department of clinical physics and bioengineering 7th
TRANSCRIPT
Department of Clinical Physics and Bioengineering
7th Symposium
Programme 2019
Queen Elizabeth Teaching and Learning Centre
7th November 2019
7th DCPB Symposium
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Contents
DCPB 7th Scientific Symposium Schedule ................................................................................................ 4
Oral Presentation Abstracts ....................................................................................................................... 5
Dr Sarah Allwood-Spiers - Safety testing of a custom-built head coil for 7T human scanning .......... 6
Peter Houston - MRI only radiotherapy planning with Varian’s HyperArc SRS system for brain metastases. .......................................................................................... 7
Dr Pauline Hall Barrientos - Review of single vs. multi-voxel spectroscopy in the paediatric MRI clinical service ............................................................................................... 8
Daniela Teixeira Macarico - Comparison of Gastric Emptying Results Using 15, 30 or 60 Minutes Sampling Over Two Hour Study – A retrospective study ............................. 9
Stephen Dacombe - Paroxysmal Atrial Fibrillation Detection .................................................... 10
Robin Sayer - Delivering virtual consultations for emergency eye care .......................... 11
Dr Ruth Hamilton - Visual outcome in children born to opioid-dependent, methadone-maintained mothers: is there a foetal opioid syndrome? ............................ 12
Poster Presentation Abstracts ................................................................................................................. 13
Poster Board Number List ........................................................................................................................ 14
1. Comparison of robustness of VMAT plan quality to shifts in patient position with either
knowledge based planning or multi-criteria optimisation for pancreas planning .................... 16
2. Can the Use of a Hydrogel Spacer Enable Intra-prostatic Boosts Without Increasing Rectal Doses? .................................................................................................................................... 18
3. Development of an alternative applicator arrangement for colpostat only brachytherapy
treatments for gynaecological cancer patients ....................................................................... 20
4. HyperArcTM radiotherapy for the treatment of Thyroid Eye Disease: a plan comparison with VMAT and 2-field parallel opposed technique ........................................................................ 21
5. De-intensification of radiotherapy dose to the elective neck in oropharyngeal squamous cell cancers .................................................................................................................................... 23
6. Assessment of Advanced Head and Neck Treatment Planning Techniques for Photon and
Proton Therapy using Post-Treatment Cone-Beam CT Scans .............................................. 25
7. Flatness and Symmetry Quality Control for Variable Dose-Rate and Arc Delivery ................ 26
8. Feasibility of Dose Escalation in Head and Neck Cancers with Multi-criteria Optimisation ... 27
9. Characterisation of 99mTc-Tektrotyd Physiological and Tumour Uptake using Standardised
Uptake Values ......................................................................................................................... 29
10. Audit of V/Q SPECT Ventilation to Perfusion Count Rate Ratios using 99mTc - Technegas/ 99mTc-MAA ........................................................................................................ 30
11. 123I FP-CIT Image Characteristics in Parkinson’s Disease and Lewy Body Dementia ........ 31
12. Serum creatinine measurement as a predictor for single sample GFR using 99mTc-DTPA . 32
13. Referral Rates and Overall Survival of Patients Receiving Ra223 Therapy for mCRCP at the Beatson West of Scotland Cancer Centre ........................................................................ 34
14. Preliminary Evaluation of Wholebody Quantitative 123I-MIBG SPECT/CT in Neuroblastoma36
15. Radionuclide Ventriculography Phase Analysis for Risk Stratification of Patients Undergoing Cardiotoxic Cancer Therapy ................................................................................................... 37
16. DaTQUANT: Beyond the Scatter-gram A Neural Network add-on to classify DaT images ... 38
7th DCPB Symposium
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17. Dose Optimisation of F18-FDG in PET for patients with weight less than 67 kg ................... 39
18. Evaluation of transplant renal vascular disease by 4D flow ................................................... 41
19. Optimisation of Functional Magnetic Resonance Imaging in Phantoms and Volunteers Using Simultaneous MultiSlice ................................................................................................ 42
20. Active Transmit/Receive Switching for Fast Field-Cycling MRI .............................................. 43
21. The Effect of B1 Variation on T1 Estimates at 7 Tesla ............................................................ 44
22. Acoustically Characterising Materials for Use in a Transcranial Ultrasound Phantom .......... 45
23. A Comparison of Nomograms to Diagnose Bladder Outlet Obstruction in Women ............... 46
24. Registration of Pre-Operative Lung Cancer PET/CT Scans with Post-Operative Histopathology Maps............................................................................................................... 47
25. A Review of Clinical Outcome Measures and Proposed Active Prosthetic Users’ Mobility Evaluation Tool Set (APUMET) .............................................................................................. 48
26. Development of Tripod Walking Aids for an Adult with Spastic Diplegia Cerebral Palsy: from
Concept to Delivery ................................................................................................................. 50
27. Augmented Reality Enhanced Ophthalmic Diagnostics ......................................................... 52
28. Does Changing Virtual Reality Scenes Alter Walking Patterns of Healthy Adults? ............... 53
29. A Virtual Reality Program for Upper Limb Rehabilitation Following Stroke ............................ 54
30. Raigmore Cath Lab: Tactics to Minimise Occupational Exposure ......................................... 56
Appendix: Scottish Trainee Event Schedule and Innovation Papers ............................................ 58
Sarah Williams - Comparison of Left Ventricular Ejection Fractions between Anger and Solid-State Gamma Cameras ..................................................................... 59
Lauren Urquhart - Impact on SPECT Reconstruction of Iterative Metal Artefact Reduction . 65
Thomas McMullan - Long-term Outcomes of Prostate Cancer Patients Treated with Low Dose Rate Brachytherapy at Edinburgh Cancer Centre ...................................... 71
Megara Srikaran - The Use of Virtual Reality Technology To Improve Radiotherapy Information for Patients With Breast Cancer .............................................. 76
7th DCPB Symposium
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DCPB 7th Scientific Symposium Schedule
Teaching & Learning Centre, Queen Elizabeth University Hospital Campus
Thursday 7th November 2019: 4pm – 7.20pm
4.00 – 5.00 pm Posters & Refreshments (Chaired by Dr Stuart Parks) Session 1: DCPB Service Updates (Chaired by Ted Mullen) (Room 006, TLC) 4.30 – 4.35 pm Welcome 4.35 – 4.40 pm Imaging – Dr Michael Bradnam 4.40 – 4.45 pm Equipment Management – Ted Mullen 4.45 – 4.50 pm Clinical Engineering – Dr Stuart Parks 4.50 – 4.55 pm Radiotherapy – Martin Glegg Session 2: John Lenihan Lecture & Oral Presentations (Chaired by Dr Michael Bradnam) (Main Lecture Theatre, TLC) 5.00 – 5.05 pm Welcome 5.05 – 5.35 pm John Lenihan Lecture – Professor David Porter 5.35 – 5.40 pm Trainee prize-giving 5.40 – 5.52 pm Dr Sarah Allwood-Spiers – Safety testing of a custom-built head coil for 7T human scanning 5.52 – 6.04 pm Peter Houston – MRI only radiotherapy planning with Varian’s HyperArc SRS system for brain metastases 6.04 – 6.16 pm Dr Pauline Hall Barrientos – Review of single vs. multi-voxel spectroscopy in the paediatric MRI clinical service 6.16 pm – 6.30 pm Posters & Refreshments Session 3: Oral Presentations (Chaired by Martin Glegg) (Main Lecture Theatre, TLC) 6.30 – 6.42 pm Daniela Teixeira Macarico – Comparison of gastric emptying results using
15, 30 or 60 minutes sampling over two hour study – a retrospective study 6.42 – 6.54 pm Stephen Dacombe – Paroxysmal atrial fibrillation detection 6.54 – 7.06 pm Robin Sayer – Delivering virtual consultations for emergency eye care 7.06 – 7.18 pm Dr Ruth Hamilton – Visual outcome in children born to opioid-dependent,
methadone-maintained mothers: is there a foetal opioid syndrome? Concluding Remarks
DCPB Symposium
Oral Presentation Abstracts
Oral Presentation: Dr Sarah-Allwood Spiers
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Safety testing of a custom-built head coil for 7T human scanning
1Allwood-Spiers S, 2McElhinney P, 1Foster J, 2Shajan G. 1Dept of Clinical Physics & Bioengineering, MRI Physics, NHS Greater Glasgow and Clyde.
2University of Glasgow
Background An 8-channel transmit, 32-channel receive head coil has been constructed at the University of Glasgow for use at the 7T clinical MRI scanner at the Imaging Centre of Excellence, Glasgow. The coil may be operated both in single channel transmit, by means of an 8x splitter, or full parallel transmission operation [1]. The radiofrequency pulses used for 7T MRI have a short wavelength, smaller than the size of the head. This causes spatial variations in the power deposition which may lead to local hotspots. We follow a rigorous safety validation before use on humans [2]. This includes modelling and experimental measurement of RF distributions and temperature rise.
Materials and Methods RF heating tests were performed using a gel phantom with similar electrical properties to the brain. The same phantom and RF heating sequence were modelled in CST [Dassault Systems, France]. For temperature measurement the PRF (proton resonance frequency) method was used: the phase change after heating the phantom was measured and converted to a temperature difference map.
Key Results SAR simulations show no significant RF deposition away from the head. In the maps of B1+ and temperature change (figure 1) good agreement was obtained: the maximum temperature rise in the simulation was 1.6°C, compared to 1.4°C in experiment.
Figure 1: (a) Simulated and (b) measured B1+ maps in a phantom [nT/V]; (c) Simulated and (d) measured maps of temperature change in a phantom after an RF heating test [°C].
Conclusion Imaging of volunteers using the new head coil is underway (figure 2). This coil shows improved coverage across the brain compared to a commercial 7T head coil. Before each use of the coil we follow a QA procedure using a phantom and in each volunteer we check the B0 and B1 field maps before continuing with further imaging.
Figure 2: TSE image using the coil in single channel transmit mode.
References [1] G Shajan, P McElhinney, S Allwood-Spiers, G Paterson, J Goense. An 8-channel transmit 32-channel receive 7T head coil for 1Tx and pTx scanner modes. Proceedings of ISMRM, Montreal, Canada, 2019. Abstract 0572. [2] Hoffmann J, Henning A, Giapitzakis IA, Scheffler K, Shajan G, Pohmann R and Avdievich NI. Safety testing and operational procedures for self-developed radiofrequency coils. NMR in Biomedicine 29(9) 1131–1144.
Oral Presentation: Peter Houston
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MRI only radiotherapy planning with Varian’s HyperArc SRS system for brain metastases.
P Houston1, W Ingram1, S Currie1
1 Radiotherapy Physics, NHS Greater Glasgow and Clyde
Background Radiotherapy planning and treatment delivery of stereotactic radiosurgery (SRS) for brain metasases is performed in Glasgow with a non-coplanar treatment technique, HyperArc [Varian Medical Systems, Palo Alto, CA, USA]. Planning is performed on a CT scan, used to derive electron density, to model dose deposition in the patient. The planning CT is fused to an MRI scan to aid delineation of the target lesions. There is evidence that compressing a patient’s pathway and reducing time from the initial MRI scan to treatment can limit growth of brain metasases and improve the management of treatment1. A potential method of compressing the patient pathway is to omit the planning CT and plan on MRI imaging. The purpose of this work is to evaluate the feasibility of MRI only radiotherapy planning with Varian’s HyperArc SRS planning solution by comparison with CT planning.
Materials and Methods Radiotherapy plans for ten patients, previously treated for cranial metastases in a single fraction, were recalculated on their diagnostic MRI scans. Selected PTVs were at least 1cc to limit partial volume effects in dose calculation due to MRI slice thickness. The MRI scans were registered, by rigid registration, to the treatment planning CT. Brain, body and bones were outlined in the MRI scans and assigned bulk HU values based on the sample of patients. Treatment plans were recalculated using the Eclipse Treatment Planning System v15.1 [Varian Medical Systems, Palo Alto, CA, USA] and AAA 15.05.07. Comparisons were made between the original CT plan, CT_Bulk with; bone, brain and water bulk assigned, MRI_Bulk with; bone, brain and water bulk assigned and MRI_Water with the entire scan assigned to 0 HU, irrespective of anatomy. Plans were compared by D99%, Dmax, Gradient Index (V40/V80), V100%, dose to OARs and dose to brain by V12Gy. Water Equivalent Depth (WED) to the geometric centre of PTV was also measured to determine the significance of bulk assigning densities.
Key Results Fitting a line to WED values for CT and MRI_Bulk gives a goodness of fit R-squared value 0.9259, indicating strong correlation (Fig.2). In comparison to the planning CT, MRI_Bulk is underestimating the WED to the PTV. Relative to the original RT plan, the average change in D99% is 0.1%, 0.9% and 2.4% and average change in DMax is 0.1%, 1.1% and 3.1% for CT_Bulk, MRI_Bulk and MRI_Water respectively (Fig.3). There is no significant change in Gradient Index V100% or V12Gy to brain. Visual differences in dose coverage of PTV are primarily at the most superior and inferior edges of PTV. This may be due to the difference in reconstructed slice thickness between MRI and CT i.e. 2.5mm vs. 1mm, and partial inclusion of PTV along those voxels.
Conclusion MRI only planning with HyperArc using bulk assignment of HU is possible and calculated doses to PTV and OARs and plan quality metrics are similar to those on an uncorrected CT. Although WED is decreased in the MRI_Bulk approach, this is not significantly affecting the dose distribution. Prior to implementing MRI only planning, further testing may be done on reconstructing the available MRI scans to a smaller slice resolution.
References [1] Salkeld AL, Hau EKC, Nahar N, et al. Changes in brain metastasis during radiosurgical planning. Int J Radiat Oncol Biol Phys 2018;102: 727-733.
Oral Presentation: Dr Pauline Hall Barrientos
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Review of single vs. multi-voxel spectroscopy in the paediatric MRI clinical service
P Hall Barrientos, H O’Neil, L McDade, M Pirie
1Department of Clinical Physics and Bioengineering, NHS Greater Glasgow and Clyde, UK 2MRI department, Royal Hospital for Children, Glasgow
Background Magnetic resonance spectroscopy (MRS) is a non-invasive measurement of metabolites in tissues. There are a number of metabolites that can be measured and in the brain there are as many as 10 that can be detected. Since MRS assesses the current metabolic status of the tissues, it is a complementary technique to anatomical MRI scans. For some patients it helps to diagnose various abnormalities. Currently at the RHC MRS is it used to help assess the extent of damaged tissue in Hypoxic-Ischaemic Encephalopathy (HIE) patients.
Materials and Methods Twenty HIE patients who had undergone MR spectroscopy as part of their MRI scan were assessed. Within this cohort ten patients had single voxel spectroscopy (SVS) method only and ten patients with multi-voxel spectroscopy (CSI) method only. Figure 1 demonstrates the difference between both methods. In total there were four MRS acquisitions performed per patient. All scans were performed on either 1.5 T Aera or 1.5 T Avanto scanner. The following assessments were made for each patient: •Total MRS scan time. This includes MRS planning and acquisition. •Quality of data. Identifying whether the acquired data was noisy and if it could be used for analysis. •Presence of lipid-contamination. If present then the data was unsuitable.
Figure 1. Left single voxel (SVS) and right multi-voxel (CSI)
Key Results It was seen that for this cohort of patients the overall MRS protocol time, for both techniques, were similar. The inter-operator variability had improved and the number of non-diagnostic scans was reduced with the CSI technique. This has an impact on the patient pathway as the number of recalled scans has decreased.
Conclusion The CSI technique also acquires data over a larger region of the brain. Therefore, we have also reduced the length of the overall MRS session if multiple regions of the brain were to be measured.
References [1] Downling C., Bollen A. W., Noworolski S. M., McDermott M. W., Preoperative Proton MR Spectroscopic Imaging of Brain Tumours: Correlation with Histopathologic Analysis of Resection Specimens, Am J of Neuro, 22, 4 2001
Oral Presentation: Daniela Teixeira Macarico
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Comparison of Gastric Emptying Results Using 15, 30 or 60 Minutes Sampling Over Two Hour Study – A retrospective study
Teixeira Macarico, D.1; Laurins, C.1; Gribben, D.1; Nicol, A.1
1NHS Greater Glasgow and Clyde – Queen Elizabeth University Hospital, New Victoria Hospital and Institute of Neurological Sciences
Background Gastric Emptying (GE) studies at Nuclear Medicine Department in the Hospitals of South of Glasgow are performed using static, erect anterior-posterior images acquired every 15 minutes for two hours. This study aims to compare the diagnostic results of the procedure using images acquired at 30 and 60-min intervals in comparison with the current protocol of 15-min intervals.
Materials and Methods Half-time of GE was obtained from curves using an exponential (or Siegel) fit. A normal T1/2 of 30-90min is used and results categorised as normal, borderline or abnormal. In Part I the pictures of 78 patients were processed for 15, 30 or 60 minutes sampling by one technologist. In Part II, 30 randomly selected patients were processed for 15 and 30 minute sampling by three technologists and Intra and Inter-Operator variability obtained.
Key Results Part I: Compared with 15min sampling, category changed in 6.4% of the patients when 60min sampling was used and 2.6% when 30min sampling was used. The average change in T1/2 is -2.49% and -1.16% respectively. Part II: There was 100% of correlation for operators 2 and 3 and a change in the category of 3.3% for the 1st Operator. For Inter-Operator variability the average of change was -2.71%.
Conclusion Using 60 or 30 minute sampling produces good results - average of overestimation of -2.49% and -1.16% respectively. There is high reproducibility of results between operators for 30-min sampling with overestimation of -2.71%. The authors found it more difficult to select the appropriate curves with 60-min sampling and don’t recommend it. For 30-min sampling, the results are the same and more data doesn’t change the clinical report. It seems reasonable to use this technique for clinical practice.
Oral Presentation: Stephen Dacombe
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Paroxysmal Atrial Fibrillation Detection Stephen Dacombe1, Tom Whiting1, Mark Watts2, Paul Britten1, Simon Rowsby1
1Medical Devices Unit, WGACH, NHS Greater Glasgow & Clyde 2Glasgow Royal Infirmary (GRI), NHS Greater Glasgow & Clyde
Email: [email protected]
Background Stroke has been a clinical priority for NHS Scotland for over 15 years. It is estimated that about 15,000 people in Scotland have a stroke each year[1]. Stroke is the leading cause of disability in Scotland and the third biggest killer in Scotland.[1] It is estimated that one in six strokes are caused by Atrial Fibrillation(AF) but it is unknown how many strokes are caused by Paroxysmal Atrial Fibrillation(PAF). AF is one of the most common irregular heart rhythms and people over the age of 40 have a lifetime risk of one in four of developing a stroke[2]. In 2016, 96,367 people in Scotland had been diagnosed with AF. It is estimated that 2.6% of the Scottish population have AF which would mean nearly 50,000 people are living with undiagnosed AF. It is unknown how prevalent PAF is in the general population. We know that 28-day continuous ECG’s pickup PAF in 15% of patients who have already suffered an ischaemic stroke[3]. Therefore, when compared to current NHS Scotland practice, we could potentially diagnose 1,326 patients, in Scotland, per year, with PAF, if we create a wearable automated AF/PAF detection system.
Materials and Methods Existing device reviews: There are many non-invasive devices claiming to detect AF, the market was initially analysed to see if any were suitable for use. Device review is an ongoing process because wearable AF detection is a hot topic and new products are continually appearing. Medical Devices Unit (MDU) capability: The MDU is evolving its skills, knowledge and capabilities. It makes sense that the MDU develops in tandem with a commercial partner in the wearable medical device field. Plan: A plan was devised to extend work previously completed with an SME, where the MDU could modify the SME’s platform to create a solution. This is a win-win for the NHS and the SME. The IP remains with the NHS and if we find a solution that works then we can discuss how the IP is licensed or bought. This project also extends the skills and knowledge base of the MDU. Proposed architecture: A commercial wireless wearable patch communicates continuously with an Android Tablet. It streams detected R-peaks as R-R intervals in near real time. The Tablet detects variation in the R-R intervals, and if the rhythm is considered not to be Normal Sinus Rhythm the patch will send a Lead II ECG trace to the tablet. From the trace the tablet will decide whether it is AF or not. If it is AF, the Tablet will alert a clinician to the trace on the server.
Key Results The system can accurately detect R peaks in noisy environments, detect arrythmias and record the ECG trace. The system shows promise to detect variations in R-R interval and store the ECG in real time. The system shows promise to last for 28 days.
Conclusion This work reports the potential of an automated AF/PAF detection system designed for use out with the hospital environment. The next stage of this project is to find the optimum position, minimise the effect of artefact, optimise the battery life and fully test in simulated environments. The following stage will require a clinical trial.
References [1] Scottish Stroke Care Audit National Report 2019 [2] Cross Party Group Report on Heart Disease and Stroke ‘A Focus on Atrial Fibrillation in Scotland’ [3] David J. Gladstone, M.D., Ph.D., Melanie Spring, M.D., Paul Dorian et al, Atrial Fibrillation in Patients with Cryptogenic Stroke, N Engl J Med 2014; 370:2467-2477
Oral Presentation: Robin Sayer
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Delivering virtual consultations for emergency eye care
Robin Sayer1, Iain Hendry1, Stephen Dacombe1, Tom Whiting1, Lindsey Steele2, Kirsten Graham2 1Medical Devices Unit (MDU), Dept of Clinical Physics & Bioengineering, West Glasgow ACH
2Glasgow Centre for Ophthalmic Research (GCOR), Dept of Clinical Phys & Bioengineering, GGH
Background Traditionally, a patient attending A&E for emergency eye care is triaged by a remote ophthalmologist who extracts key details over-the-phone from non-ophthalmic experts' description. The referring departments have variable experience with eye disease and eye examination equipment so information relayed to the ophthalmologist may not be optimal for triage. This can result in additional patient appointments in the Acute Referral Centre or ophthalmologists travelling to the A&E site. Tele-ophthalmology (remote triage via video feed) is being trialled as a solution, enabled through the use of bespoke mobile device (e.g. iPad) adaptors
Materials and Methods A proof of concept tele-ophthalmology slit lamp adaptor was developed by the University of Strathclyde (UoS) for initial deployment in NHS Forth Valley (FV). The MDU refined the design and is manufacturing new devices to suit slit lamps in GG&C and other health boards under its ISO 13485 certified Quality Management System (QMS). The MDU device has been designed and developed under the Health Care Institution Exemption (HIE) of the Medical Devices Regulations (MDR). Although the MDR doesn’t come into full force until May 2020, it’s been adopted early by the MDU as best practice for in-house medical device design and manufacture. The MDU is now developing a retinal imaging adaptor for use in FV and GG&C, based on another UoS proof of concept device. The use of slit lamp devices in GG&C and FV has been evaluated through user and patient surveys.
Key Results Slit lamp adaptor use in FV has been beneficial in terms of patient/clinician satisfaction, time-saving and prevention of unnecessary clinic reviews. Overall, both clinicians and patients report high levels of satisfaction. An appointment in secondary care was deemed to be obviated in 73% s.d+/-3.5 of cases. However, a more limited uptake of the system was experienced in the QEUH due to less experienced receiving ophthalmologists (the most junior of a 3-tier system) with a preference for direct examination rather than decision making based on a relayed examination. The trial is being extended to the RAH where the receiving ophthalmologists are more experienced.
Conclusion Tele-ophthalmology offers potential for significant cost savings without compromising high standards of service delivery, but uptake is highly dependent on the experience of the receiving ophthalmologists.
References [1] Legarreta, J.E., Conner, I.P., Loewen, N.A. et al. The Utility of iPhone-based imaging for tele-ophthalmology in a triage capacity for emergency room consultations. Invest Ophthalmol Vis Sci. 2014;55. [2] Kulshrestha M, Lewis D, Williams C, Axford A. A pilot trial of tele-ophthalmology services in north Wales. J Telemed Telecare. 2010;16(4):196-197. [3] Poyser & I Livingstone. Lessons Learned from a Scottish Tele-Ophthalmology Pilot Project
Oral Presentation: Dr Ruth Hamilton
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Visual outcome in children born to opioid-dependent, methadone-maintained mothers: is there a foetal opioid syndrome?
R. Hamilton1,2, A. Mulvihill3, K. Spowart4, D.L. McCulloch5, H Mactier6,2
1Department of Clinical Physics & Bioengineering, Royal Hospital for Children, NHS GG&C, Glasgow, UK;
2College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK; 3Paediatric Ophthalmology, Princess Alexandra Eye Pavilion, NHS Lothian, Edinburgh, UK;
4Childrens Visual Impairment Services, William Street Clinic, NHS GG&C, Glasgow, UK; 5Princess Royal Maternity, NHS GG&C, Glasgow, UK.
Background Previously, abnormal visual evoked potentials (VEPs), independently associated with methadone exposure, and abnormal visual findings at six months were reported in a cohort of children born to opioid-dependent, methadone-maintained mothers but not in comparison children. The aim of this study was to describe long-term, follow-up vision findings in the same cohort. ClinicalTrials.gov: NCT03603301.
Materials and Methods Children born in 2008–10 at Princess Royal Maternity, Glasgow and previously enrolled in the Vision in Drug-Exposed Infants (VIDI) study attended for comprehensive visual assessment. In utero drug exposure was previously established via maternal antenatal urine and infant urine and meconium samples. Acuities (distance and near), stereovision, binocular fusion, strabismus, eye movements (subjective and infra-red remote tracking), nystagmus, VEPs, fundoscopy and retinoscopy were assessed. Researchers were masked to exposure status.
Key Results 20 drug-exposed and ten comparison children attended, aged 8–10 years: groups were matched for neonatal parameters of birthweight, gestation, feeding, socio-economic status and head circumference but not for maternal smoking or excess alcohol use. Drug-exposures included methadone (19/20), opiates (18/20), benzodiazepine (15/20), cannabis (12/20), cocaine (4/20) and amphetamine (4/20). 11/20 drug-exposed and 1/10 comparison children ‘failed’ visual assessment. Drug-exposed children failed with a combination of strabismus, poor acuity, poor binocular function and/or nystagmus.
Conclusion The drug-exposed children with abnormal vision were all exposed to opioids (methadone and/or heroin) and most also to benzodiazepine. Their pattern of abnormalities supports failure of binocular vision development, and extends similar findings reported worldwide. Additional neurodevelopmental problems are associated with opioid exposure. We postulate an opioid teratogenic effect causing loss of binocular connections within the striate cortex. Despite the challenges of adequate environmental or socio-economic control in comparison children, there appears to be a foetal opioid syndrome which includes the visual problems described here. Funders: Tenovus Scotland; Glasgow Children’s Hospital Charity; Action Medical Research UK; Chief Scientist Office (Scotland).
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DCPB Symposium
Poster Presentation Abstracts
7th DCPB Symposium
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Poster Board Number List
1. Peter Houston - Comparison of robustness of VMAT plan quality to shifts in patient position with either knowledge based planning or multi-criteria optimisation for pancreas planning
2. Nikki Laverick - Can the Use of a Hydrogel Spacer Enable Intra-prostatic Boosts Without Increasing Rectal Doses?
3. Dr Susan Morris - Development of an alternative applicator arrangement for colpostat only brachytherapy treatments for gynaecological cancer patients
4. Dr Ronan Valentine - HyperArcTM radiotherapy for the treatment of Thyroid Eye Disease: a plan comparison with VMAT and 2-field parallel opposed technique
5. Dr Ronan Valentine - De-intensification of radiotherapy dose to the elective neck in oropharyngeal squamous cell cancers
6. David Church - Assessment of Advanced Head and Neck Treatment Planning Techniques for Photon and Proton Therapy using Post-Treatment Cone-Beam CT Scans
7. Kate Sexton - Flatness and Symmetry Quality Control for Variable Dose-Rate and Arc Delivery
8. Dr Laura Grocutt - Feasibility of Dose Escalation in Head and Neck Cancers with Multi-criteria Optimisation
9. Caitlin Reilly - Characterisation of 99mTc-Tektrotyd Physiological and Tumour Uptake using Standardised Uptake Values
10. Daniela Teixeira Macarico - Audit of V/Q SPECT Ventilation to Perfusion Count Rate Ratios using 99mTc - Technegas/ 99mTc-MAA
11. Dr Alice Nicol - 123I FP-CIT Image Characteristics in Parkinson’s Disease and Lewy Body Dementia
12. Gary Hilland - Serum creatinine measurement as a predictor for single sample GFR using 99mTc-DTPA
13. Iain Kerr - Referral Rates and Overall Survival of Patients Receiving Ra223 Therapy for mCRCP at the Beatson West of Scotland Cancer Centre
14. Hugh Wallace - Preliminary Evaluation of Wholebody Quantitative 123I-MIBG SPECT/CT in Neuroblastoma
15. Kirsty Jones - Radionuclide Ventriculography Phase Analysis for Risk Stratification of Patients Undergoing Cardiotoxic Cancer Therapy
16. Jennifer McCormick - DaTQUANT: Beyond the Scatter-gram A Neural Network add-on to classify DaT images
17. Jennifer Summersgill - Dose Optimisation of F18-FDG in PET for patients with weight less than 67 kg
18. Dr Pauline Hall Barrientos - Evaluation of transplant renal vascular disease by 4D flow
19. Amy Morton - Optimisation of Functional Magnetic Resonance Imaging in Phantoms and Volunteers Using Simultaneous MultiSlice
20. Christopher Taylor - Active Transmit/Receive Switching for Fast Field-Cycling MRI
21. George Bruce - The Effect of B1 Variation on T1 Estimates at 7 Tesla
22. Eilidh Avison - Acoustically Characterising Materials for Use in a Transcranial Ultrasound Phantom
7th DCPB Symposium
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23. Craig Lees - A Comparison of Nomograms to Diagnose Bladder Outlet Obstruction in Women
24. Gabriel Reines March - Registration of Pre-Operative Lung Cancer PET/CT Scans with Post-Operative Histopathology Maps
25. Clodagh Duffy - A Review of Clinical Outcome Measures and Proposed Active Prosthetic Users’ Mobility Evaluation Tool Set (APUMET)
26. Clodagh Duffy - Development of Tripod Walking Aids for Adults with Spastic Diplegia Cerebral Palsy: from Concept to Delivery
27. Olivia Lala - Augmented Reality Enhanced Ophthalmic Diagnostics
28. Rachel Jackson - Does Changing Virtual Reality Scenes Alter Walking Patterns of Healthy Adults?
29. Sarah Francis - A Virtual Reality Program for Upper Limb Rehabilitation Following Stroke
30. Rebecca Stace - Raigmore Cath Lab: Tactics to Minimise Occupational Exposure
Poster Presentation: Peter Houston
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Comparison of robustness of VMAT plan quality to shifts in patient position with either knowledge based planning or multi-criteria optimisation for
pancreas planning
P. Houston Radiotherapy Physics, NHS Greater Glasgow and Clyde
Background Radiotherapy treatment planning for abdominal sites is complicated by abdominal motion causing target and organs at risk (OAR) to move and by difficulty in distinguishing targets which comprise of soft tissue on on kV imaging. As radiotherapy planning has advanced and become more conformal, facilitating greater OAR sparing, the robustness of plan quality to target motion has to be considered. The purpose of this work is to perform a comparison of the robustness of two treatment planning optimisation methods to shifts in patient position for VMAT Pancreas Planning. The optimisation methods investigated were a knowledge based planning solution, RapidPlan (RP v15.5), and a multi-criteria optimisation solution (MCO v15.5).
Materials and Methods Knowledge based planning was performed with RP. Multi-criteria optimisation was performed with MCO. All plans were normalised to a PTV mean of 100% dose. RP generates estimated DVHs and planning objectives based on the library of plans it is built from. MCO is a planning trade off tool that calculates multiple plans for each planning objective; this allows the planner to explore the Pareto surface of the ideal dose distribution to determine the optimal trade off between PTV coverage and OAR doses. RP and MCO were applied to 10 Pancreas planning cases. Previous work, Houston P., Laverick N. Planning comparison of knowledge based planning and multi-criteria optimisation for VMAT pancreas planning. ESTRO 2017 compared the plans with regards to plan quality. The treatment plans were investigated for robustness to patient set-up by shifting the patient and re-measuring dose volume statistics. Plans were shifted ±0.3cm and ±0.5cm in the x, y and z directions and worst case dose values recorded for each PTV and OAR.
Key Results
Figure 1:Robustness of GTV & PTV to a variety of set-up errors
Robustness of PTV and GTV coverage to set-up Errors
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4200.0
4400.0
4600.0
4800.0
5000.0
Mean PTV D 98% Mean PTV D 95% Mean GTV D98%
Do
se (
cG
Y)
RP no shift
RP 0.3cm shift
RP 0.5cm shift
MCO No Shift
MCO 0.3cm Shift
MCO 0.5cm shift
1
Poster Presentation: Peter Houston
17
MCO v15.5 and RP v15.5 plans show comparable robustness to 0.3cm shifts. MCO v15.5 gives higher PTV D98% coverage after a 0.5cm shift than RP v15.5. GTV coverage is not significantly affected by either a 0.3cm or 0.5cm shift, as expected due to GTV to PTV margins of 1cm.
Figure 2: Robustness of ipsilateral kidney to a variety of et-up errors.
The improvements in Plan Quality with MCO conferred a significant advantage in the robustness of OAR dose to shifts in patient position. Average ipsilateral kidney D50% was lower with MCO v15.5 shifted 0.5cm when compared to unshifted RP plans, 837cGy and 1200cGy respectively.
Duodenum, which is often the dose limiting organ in pancreas planning, did not display a significant change in robustness of D33% or D2cc
Conclusion MCO treatment planning does not degrade the robustness of PTV coverage to shifts in patient position and may in some cases improve that robustness. Robustness of OAR doses to set-up shift uncertainties are either comparable or improved when planned with MCO. This general robustness to changes in patient shifts indicates that current margining, imaging and set-up protocols are appropriate for MCO planned pancreatic radiotherapy treatments.
Robustness of Ipsilateral Kidney to Set-up Errors
500
1000
1500
2000
2500
3000
3500
D50% D2cc
DVH parameter
Do
se (
cG
y)
RP no shift
RP 0.3cm Shift
RP 0.5cm shift
MCO no shift
MCO 0.3cm Shift
MCO 0.5cm shift
Poster Presentation: Nikki Laverick
18
Can the Use of a Hydrogel Spacer Enable Intra-prostatic Boosts Without Increasing Rectal Doses?
N. Laverick1, S. Currie2
1Radiotherapy Physics, Beatson West of Scotland Cancer Centre
Background
Rectal spacers are devices inserted between the rectum and the prostate prior to radiotherapy treatment, with the aim of potentially reducing doses to organs at risk and the incidence of side effects. This planning study aimed to assess the impact of a hydrogel spacer (SpaceOAR®, Boston Scientific) on plan quality when an intra-prostatic focal boost was included.
Materials and Methods Treatment plans were created on scans of ten patients pre- and post-implantation of the hydrogel spacer. All plans used VMAT with two coplanar arcs to treat the prostate to 60Gy in 20 fractions (PTV60) and the seminal vesicles to 47Gy (PTV47). All plans were optimised using the Centre’s RapidPlan model (Varian Medical Systems). A boost volume was then identified for each patient and outlined on both the pre- and post- scan sets with the aid of MRI imaging. These volumes were planned to two separate dose prescriptions, 67Gy and 78Gy. Plans were compared in terms of target coverage and doses to bladder and rectum. For the plans without the focal boost and the 78Gy boost plans, the robustness of the OAR doses was also assessed by inducing a 5mm target shift in all directions and recording the poorest rectal and bladder doses.
Key Results Target coverage was not affected by the presence of the hydrogel spacer; however rectal doses were reduced post-implantation. As Figure 1 shows, the volume of rectum receiving both intermediate and higher doses is reduced with the spacer. The implantation of the spacer has allowed boosting of an intra-prostatic volume to 78Gy whilst still achieving lower rectal doses than the treatment plans produced on the pre-implantation scans with no boost volume. Significant increases were found in rectal dose when boosting without the hydrogel spacer, whereas increases with boosting with the spacer in place were not significant. The mean dose to the rectum, which is associated with faecal incontinence and high stool frequency following radiotherapy, is also reduced; the reduction is such that similar levels (p = 0.04) are achieved for the pre-implantation with no boost (median 19.6Gy) and the post-implantation with 78Gy boost (median 17.0Gy). No overall change in bladder dose was seen.
Figure 3: Median values of rectal DV statistics pre and post implantation of hydrogel spacer for different boost dose prescriptions.
Median Rectal DV Statistics
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
V24Gy V32Gy V40Gy V48Gy V52Gy V56Gy V60Gy
% V
olu
me r
eceiv
ing
do
se
Pre, No Boost
Pre, 67Gy Boost
Pre, 78Gy Boost
Post, No Boost
Post, 67Gy Boost
Post, 78Gy Boost
2
Poster Presentation: Nikki Laverick
19
As seen in Figure 2, the worst-case increase in rectal doses was reduced when using the hydrogel spacer, especially at higher dose levels which are associated with rectal bleeding. No meaningful change in the robustness of bladder dose was observed.
Figure 4: Median "worst case" increases in rectal DV statistics when shifting target by 5mm.
Conclusion The implantation of the hydrogel spacer enables the use of intra-prostatic focal boosts whilst maintaining similar or reduced rectal doses to those achieved pre-implantation and also improving the robustness of these doses to PTV shifts.
Median "worst case" increase in rectal doses after 5mm target shift
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
V24Gy V32Gy V40Gy V48Gy V52Gy V56Gy V60Gy
Incre
ase i
n v
olu
me r
eceiv
ing
do
se (
%)
Pre, No Boost
Pre, 78Gy Boost
Post, No Boost
Post, 78Gy Boost
Poster Presentation: Dr Susan Morris
20
Development of an alternative applicator arrangement for colpostat only brachytherapy treatments for gynaecological cancer patients
Susan Morris, Fergus Rattray
Radiotherapy Physics, Dept of Clinical Physics & Bioengineering, The Beatson West of Scotland Cancer Centre
Background Colpostat only brachytherapy treatments are part of the standard treatment for post-hysterectomy gynaecological cancer patients. The colpostat applicators are nearing their maximum number of sterilistation cycles and are no longer supported by the manufacturer. As a result an alternative applicator arrangement is required. It has been suggested that using the ring only from a plastic ring and tandem applicator set could be a viable option.
Method 10 colpostat patients (20 plans), with a range of applicator sizes, have been re-planned using the plastic ring only from a standard 60º ring and tandem applicator in an attempt to emulate the original dose distribution. Various parameters have been analysed in order to assess whether or not an acceptable plan could be produced using this new arrangement.
Results Measurements of the total insertion diameter of the colpostat applicators varied from 4.0-5.4cm. The diameter of the plastic ring is 3.2cm without the cap, or 4.0cm with the cap which would suggest that it could have been accommodated for all patients in the study. Using the available source positions in the ring applicator it was possible to emulate the dose distribution produced in the original plans. Dice co-efficients of similarity of 0.93-0.97 were achieved for the distributions. An increase in the dose to tissue at the surface of the applicator was found due to the difference in the displacement of this tissue by the applicator. However these doses were comparable to those routinely found in other standard intra-cavitary brachytherapy treatments. Differences between the geometry of the two applicators mean that the source channel in the ring is closer to the surface of the applicator and hence potentially closer to OARs resulting in higher doses (see figure 1). It was found that the bladder D2cc (dose to the maximally irradiated 2cm3) breached the tolerance in 6/20 plans. The rectum and bowel doses were well within the acceptable limits for all plans. This suggests that the bladder will be the limiting organ in this process.
Figure 1 – (a) Distance from the source channel to the edge of the applicator in the ring and medium colpostat.
For the standard colpostat arrangement the normalisation point is positioned at 5mm from the surface of the applicator. However it became apparent that this is not appropriate for use with the ring applicator. Analysis of all the new ring plans showed that the 100% isodose line consistently fell at a distance of 1.6cm from the surface of the source channel and is therefore proposed as a suitable reference point for such plans.
Conclusion This work has shown that treating brachytherapy patients using a plastic ring only applicator arrangement is a viable option with respect to accommodation of the applicator in the patient anatomy and also the creation of an acceptable dose distribution. Consideration should be given to the variation in OAR doses and changes required to the planning technique.
3
Poster Presentation: Dr Ronan Valentine
21
HyperArcTM radiotherapy for the treatment of Thyroid Eye Disease: a plan comparison with VMAT and 2-field parallel opposed technique
Ronan Valentine1, Stefano Schipani2,3, Paul Cauchi4, Vikas Chadha4, Julie Connolly4, Tim Mitchell2,
Diana Ritchie2, Suzanne Currie1 1Beatson West of Scotland Cancer Centre, Radiotherapy Physics Department, Glasgow, UK
2Beatson West of Scotland Cancer Centre, Radiation Oncology Department, Glasgow, UK 3University of Glasgow, Institute of Cancer Sciences, Glasgow, UK
4Gartnavel General Hospital, Tennent Institute of Ophthalmology, Glasgow, UK
Background To compare HyperArcTM (HA) radiotherapy with 2-field VMAT (2F-V) and 2-field parallel opposed (2F-PO) technique for the treatment of Thyroid Eye Disease (TED).
Materials and Methods Patients with high dose steroid refractory TED were selected. The patients were immobilized with a stereotactic radiosurgery (SRS) encompass shell. A non-contrast enhanced CT was acquired with 1mm slices for planning purposes. CT was fused with a baseline diagnostic MRI to better define the Organs at Risk (OARs). CTV was defined as the bilateral retro-ocular soft tissues including the ocular muscles and the retro-bulbar fat and excluding the lacrimal glands with a 3mm margin. CTV was expanded to PTV with a 2mm margin. Lenses, optic chiasm, brain, lacrimal ducts, brainstem, hippocampus, pituitary, nasal cavity and lacrimal glands were defined as OARs. HA, 2F-V and 2F-PO plans were generated with Eclipse TPS v15.5 (Varian Medical Systems, Palo Alto, CA, USA). HA used up to 4 arc fields, 3 of which were non-coplanar, optimised collimator angles and a SRS normal tissue objective (NTO) function for plan optimisation. 2F-V plans consisted of two full rotational arcs. HA and 2F-V plans were generated using high definition 2.5 mm leaf width MLCs along with a 1.25 mm optimisation resolution and grid size. 2F-PO plans were constructed with both anterior field edges placed posterior to the lenses and the posterior field edges covering the orbital apex. All plans were generated using a photon beam energy of 6MV, a dose rate of 600 MU/min, and a dose prescription of 2004 cGy in 12 fractions to the PTV. Dosimetric parameters for PTV and organs at risk (OARs) were evaluated.
Key Results Ten patients were included in the study. HA plans offered superior PTV coverage (p<0.05) at particular dose metrics compared to 2F-V (D99%, D98%) and 2F-PO (D99%, D98%, D95%, D50%). For the HA plans, Dmean to the brain, brainstem, hippocampus, pituitary and nasal cavity were reduced (p<0.05) compared to the 2F-V plans. Also, for the 2F-PO plans, Dmax to optic chiasm, Dmean to lacrimal ducts, nasal cavity, lacrimal glands was higher (p<0.05) and Dmax to lenses lower (p<0.05) compared to the HA and 2F-V plans. The dosimetric results are reported in Table 1.
Conclusion HA offers a good compromise between PTV coverage and OARs sparing especially for lenses and lacrimal glands with possible advantage in TED symptom control and long term complications (cataract and ocular dryness). A prospective study will be carried out in our institution.
4
Poster Presentation: Dr Ronan Valentine
22
Table 1. Dosimetric results for PTV and OARs (n = 10 patients)
HyperArc (HA) 2F- VMAT 2F-PO
Constraint Dose (%)
PTV
D99% 91.6 ± 3.9 89.0 ± 6.3 6.3 ± 2.1
D98% 94.0 ± 2.1 92.4 ± 3.1 8.2 ± 3.4
D95% 96.2 ± 1.5 95.1 ± 2.5 16.0 ± 7.6
D50% 101.8 ± 0.6 101.5 ± 1.5 99.6 ± 0.8
D5% 105.8 ± 1.1 105.8 ± 2.1 103.2 ± 0.8
D2% 106.9 ± 1.3 106.9 ± 2.2 104.1 ± 1.0
OARs Dose (Gy)
Optic Chiasm
Dmax
5.1 ± 1.4 6.5 ± 3.2 10.2 ± 6.9
Left Lens 5.7 ± 1.9 5.9 ± 1.1 2.3 ± 1.8
Right Lens 5.8 ± 1.9 5.8 ± 1.3 1.6 ± 0.8
Brain
Dmean
2.5 ± 0.2 2.6 ± 0.2 1.0 ± 0.2
Lacrimal Ducts 8.4 ± 3.4 9.5 ± 3.2 11.4 ± 6.9
Brainstem 2.5 ± 0.5 3.4 ± 1.4 0.2 ± 0.02
Hippocampus 2.6 ± 0.4 3.9 ± 1.3 0.2 ± 0.02
Pituitary 2.8 ± 0.6 4.2 ± 2.3 2.0 ± 1.4
Nasal Cavity 7.8 ± 1.7 11.5 ± 2.8 13.5 ± 1.5
L Lacrimal Gland 8.6 ± 4.2 9.5 ± 3.9 17.1 ± 2.3
R Lacrimal Gland 8.6 ± 4.0 9.4 ± 4.0 16.8 ± 2.9
Poster Presentation: Dr Ronan Valentine
23
De-intensification of radiotherapy dose to the elective neck in oropharyngeal squamous cell cancers
Ronan Valentine1, Amy Martin2, Claire Paterson2, Suzanne Currie1.
1Beatson West of Scotland Cancer Centre, Radiotherapy Physics Department, Glasgow, UK. 2Beatson West of Scotland Cancer Centre, Radiation Oncology Department, Glasgow, UK
Background The incidence of oropharyngeal squamous cell cancer (OPSCC) is rising due to Human Papilloma Virus (HPV) infection. HPV-positive (HPV+) OPSCC has a good prognosis and is sensitive to treatment. Standard of care is high dose radiotherapy which is very effective but causes significant and permanent toxicity. There is a consensus that investigation into less toxic treatments for these patients is required. A retrospective planning study was carried out evaluating the effect of delivering a reduced radiotherapy dose to the elective neck, known as Planning Target Volume (PTV_LR) on dose received by the organs at risk (OARs).
Materials and Methods Ten representative patients (HPV+, non-smokers, OPSCC) were re-planned retrospectively using Eclipse TPS v15.5 [Varian Medical Systems, Palo Alto, CA, USA], RapidPlan® (RP) and multi-criteria optimisation (MCO). All plans consisted of two VMAT fields with two full rotational arcs at 6 MV and 600 MU/min. In our centre, head & neck squamous cancers are typically prescribed 65Gy in 30 fractions to gross disease; High Risk Planning Target Volume (PTV_HR) while the PTV_LR is treated to 54Gy in 30 fractions (50Gy equivalent). The original clinical plans were re-optimised with a locally published RapidPlan® model and MCO to achieve optimal PTV coverage while maintaining OAR sparing consistent with our centre’s specified dose constraints. Subsequently, all plans were similarly re-optimised only this time PTV_LR was prescribed 42.1Gy in 30 Fractions [40Gy (EQD2Gy)] while retaining 65Gy to PTV_HR. Finally, plan deliverability for all plans was assessed using the modulation factor (MF) and MLC average leaf pair opening (ALPO).
Key Results Table 1 highlights the dose differences found between PTV_HR, PTV_LR and pertinent OARs when comparing between the 54Gy and 42.1Gy prescriptions to PTV_LR. Acceptable and within protocol, PTV_HR coverage was still achieved for 42.1Gy with only a small % reduction found in the D99% and D95% constraints. Comparing between the prescriptions, the dose constraints for PTV_LR were clinically acceptable with each of the appointed OAR doses significantly reduced for 42.1Gy (p<0.05). On average, we found the MF to be 0.40 and 0.46 and the ALPO to be 2.9 and 3.0 for the 54Gy and 42.1Gy plans, respectively, suggesting highly deliverable plans.
Conclusion By reducing the dose from 54Gy to 42.1Gy to PTV_LR, we found a significant reduction in OAR doses while maintaining acceptable doses to the PTV_HR. Due to steep dose response curves seen in OARS, we anticipate that this reduction in radiotherapy dose will translate into potentially important toxicity gains for patients. This approach is likely to be safe due to maintained dose to gross disease yet with potential clinically relevant reductions in dose received by OARS. On the basis of these results a larger dosimetric study is in progress and will form the basis for the radiotherapy protocol and QA work for a clinical trial investigating this strategy.
5
Poster Presentation: Dr Ronan Valentine
24
Table 1. Dose differences between 54Gy and 42.1Gy prescriptions (n = 10 patients)
Dose Prescribed to PTV_LR
PTV Coverage/Constraint 54Gy 42.1Gy Reduction
(%)
Dose (%)
D99% > 90% 93.4 ± 0.9 90.6 ± 0.5 -3.0
PTV_HR D95% > 95% 96.1 ± 0.5 95.2 ± 0.3 -0.9
65Gy D5% < 105% 103.8 ± 0.3 103.8 ± 0.4 0.0
D2% < 107% 104.5 ± 0.4 104.7 ± 0.5 0.2
D99% > 90% 93.0 ± 0.7 90.8 ± 0.7 -2.4
PTV_LR D95% > 95% 96.2 ± 0.4 95.5 ± 0.5 -0.7
D5% 109.1 ± 0.8 116.9 ± 3.8 7.1
D2% 113.6 ± 1.2 129.7 ± 3.7 14.2
OARs Dmean (Gy)
Ipsilateral Parotid 32.5 ± 11.4 29.3 ± 11.8 -9.8
Contralateral Parotid 20.6 ± 3.7 15.6 ± 2.6 -24.3
Larynx 42.8 ± 5.9 39.3 ± 6.2 -8.2
Constrictor Muscles 57.2 ± 2.2 50.9 ± 2.7 -11.0
Poster Presentation: David Church
25
Assessment of Advanced Head and Neck Treatment Planning Techniques for Photon and Proton Therapy using Post-Treatment Cone-Beam CT Scans
David Church1, Ronan Valentine2, Suzanne Currie2, Peter Houston2, Eliane Miguel-Chumacero2, Lisa
Hay2, Claire Paterson1. 1Beatson West of Scotland Cancer Centre, Radiotherapy Physics Department, Glasgow, UK.
2Beatson West of Scotland Cancer Centre, Radiation Oncology Department, Glasgow, UK
Introduction Dosimetric advantages of proton therapy compared to photon radiotherapy for head and neck cancer (HNC) have been reported at baseline. However, it is well recognised that patient contour can change significantly during a multi-week course of radical treatment for HNC affecting the delivery of planned dose. This is of particular concern with proton therapy given its highly conformal nature. The aim of this study was to compare dosimetry at baseline and throughout treatment with robust optimised Intensity Modulated Proton Therapy (IMPT) and photon Volumetric Arc Radiation Therapy (VMAT)
Materials/Methods 11 patients with locally advanced oropharyngeal cancer were included. 5 plans were made for each patient:
a) RapidplanTM (RP) b) RP+Multi-Criteria Optimisation (MCO) c) IMPT- (no robustness criteria) d) IMPT+3mm (3mm perturbations included in the optimisation process) e) IMPT+5mm (5mm perturbations included in the optimisation process).
Synthetic CT (sCT) scans were created from the registration of the weekly CBCTs and the original planning CT (pCT) scans of each patient using VelocityTM. Using these sCT scans, verification plans were created from the original plans for each patient. For 10 patients there were 6 sCT plans per treatment per patient and for 1 patient there was 5. Prescribed dose and fractionation for each patient was 65Gy in 30 fractions for the high-risk PTV (defined as gross disease with a margin and entirety of involved nodal level) and 54Gy in 30 fractions for the low-risk PTV (defined as areas considered at risk of containing microscopic disease). The PTV margins for all patients were 3mm added isotropically to CTV. A PRV of 3mm was applied to critical organs at risk (OARs). ‘Larynx’ was used to describe the midline mucosa from hyoid to cricoid.
Results Target volume coverage was acceptable during 6 weeks of treatment with RP, MCO, IMPT+5. IMPT+3 and IMPT- resulted in inadequate CTV coverage during radical treatment. Dose to PRV brainstem and spinal cord was acceptable with all modalities throughout treatment. IMPT- achieved the lowest dose to contralateral parotid (17.6 ± 7.9Gy) with similar doses seen with RP (22.0 ± 7.3Gy), MCO (20.6 ± 6.3Gy) and IMPT+3 (20.7 ± 9.2Gy). IMPT+5 resulted in higher doses to contralateral parotid (25.4 ± 9.9Gy). A similar pattern was seen with mean dose to larynx; IMPT- (33.1 ± 12.6Gy), RP (40.5 ± 11.4Gy), MCO (39.8 ± 11.9Gy), IMPT+3mm (35.1 ± 14.1Gy) and IMPT+5mm (41.4 ± 12.9Gy)
Conclusions Robustness of 5mm is required when planning HNC treatment with protons to ensure adequate target coverage throughout 6 weeks of treatment. This results in increased dose to contralateral parotid and larynx compared to RP or MCO. The dosimetric advantages for OAR sparing, previously demonstrated with proton therapy compared to photon therapy for HNC, are lost when robustness is added to ensure adequate target volume coverage throughout treatment. Advanced photon planning techniques such as MCO result in better OAR sparing while maintaining CTV coverage.
6
Poster Presentation: Kate Sexton
26
Flatness and Symmetry Quality Control for Variable Dose-Rate and Arc Delivery
Kate Sexton1, Megan Couper2, Natalie McInally2
1Department of Clinical Physics and Bioengineering, Health Physics, Gartnavel Royal Hospital, Glasgow
2Department of Radiotherapy, Ninewells Hospital, Dundee
Background Currently, as part of the monthly linear accelerator (linac) quality control (QC) in the Radiotherapy Department of Ninewells Hospital, Dundee, Sun Nuclear’s IC Profiler (ICP) is used for routine beam flatness and symmetry measurements for open and wedged field photon beams at static gantry angles. To ensure accurate dose delivery in dynamic mode, the field flatness and symmetry should be equal to the baseline profile in static mode throughout gantry rotation. Since treatment planning systems (TPSs) rely on data acquired at gantry 0°, beam profiles must be stable during gantry rotation and while dose rate is altered. International guidance recommends that flatness and symmetry should be evaluated during arc delivery and at a range of dose rates that will be used for VMAT, with values better than 2% at all dose rates compared to the baseline values for 0° gantry angle and a dose rate of 600 monitor units per minute (MU/min). Due to the continuously changing field shape and gantry angle, VMAT plans generally consist of more dose segments at low dose rates than in IMRT plans, to meet the speed-limiting properties of the various linac components.
Materials and Methods The Sun Nuclear Corporation IC Profiler (ICP) is a device containing ionisation chambers along the x- and y-axes and along the diagonals. The profiler is attached to the gantry via a custom jig, which positions it at a fixed source-to-surface distance (SSD). Data was taken on the Varian TrueBeam linac in treatment room 3. The ICP was attached to the treatment head using the gantry mount with SSD of 75 cm. Field size was set to 35 cm × 35 cm for each beam. Fixed dose rates of 40, 60, 100, 200, 400 and 600 MU/min were used as the beam was delivered through gantry rotation from 182° and 302° and at static gantry angles of 0° and 270°. 50 MU were delivered for static gantry angles. The baseline values were taken as those obtained for flatness and symmetry at a dose rate of 600 MU/min at gantry angle 0°. Flatness and symmetry were calculated using ICP software as well as Varian DoseLab software. These results were compared and then assessed with current the QC tolerance level of ±0.5 %.
Key Results ICP and DoseLab values for symmetry were in good agreement, with a range of X values of 0.4% and of Y values of 0.2% over the delivered dose rates. Discrepancies between calculations were evident at lower dose rates, perhaps due to decreased statistics. However, all values were within the tolerance values of baseline ±5% for both X and Y profiles. Time averaged ICP flatness results were found to agree well with flatness values calculated in DoseLab. Discrepancy at the dose rate of 40 MU/min may be due to the large variability in flatness observed at this low dose rate, in conjunction with inherent decreased statistics. It was consistently seen for static and VMAT delivery that flatness worsened with decreasing dose rate. In addition, throughout delivery of both static and VMAT beams at 40 MU/min and 60 MU/min dose rates, flatness frequently exceeded tolerance values.
Conclusion IC Profiler has been used successfully to assess beam flatness and symmetry at static gantry angles and during VMAT beam delivery at a variety of dose rates. It has been shown that dose rates > 100 MU/min have flatness and symmetry values within tolerance of the 600 MU/min at gantry 0° baseline, and as such, do not require frequent assessment. Further investigation is recommended into flatness and symmetry at lower dose rates as well as an investigation into changing dose rates during beam delivery.
7
Poster Presentation: Dr Laura Grocutt
27
Feasibility of Dose Escalation in Head and Neck Cancers with Multi-criteria Optimisation
L. Grocutt1, S. Currie1, C. Paterson2, A. Martin2, R. Valentine1 1Beatson West of Scotland Cancer Centre, Radiotherapy Physics Department
2Beatson West of Scotland Cancer Centre, Radiation Oncology Department
Background The incidence of oropharyngeal squamous cell cancer (OPSCC) has increased in recent years, while a considerable portion of intermediate and high risk HPV- patients with a significant smoking history continue to relapse despite radical radiotherapy. This current study investigates whether increasing the delivered radiotherapy dose to the gross tumour volume (GTV) to 84 Gy is feasible while maintaining optimal PTV coverage along with acceptable organs at risk (OARs) doses.
Material /Methods Ten representative patients (HPV-, smokers) with high risk, locally advanced OPSCC, were re-planned retrospectively using Eclipse TPS 15.5 [Varian Medical Systems, Palo Alto, Ca, USA], RapidPlan® (RP) and multi-criteria optimisation (MCO). All plans consisted of two VMAT fields with two full rotational arcs at 6 MV and 600 MU/min. At our centre, OPSCCs are typically prescribed 65 Gy in 30# to the high risk planning target volume (PTV_65) while the low risk PTV_54 is treated to 54 Gy in 30#. The original clinical plans were re-optimised with a locally published RP model and MCO to achieve an escalated dose to the GTV (84 Gy in 30# ) while achieving comparable PTV coverage and OAR sparing consistent with our centre’s specified dose constraints. Comparisons were made between the 1) clinically reviewed plans and four additional groups consisting of the clinical plans re-optimised with 2) RP, 3) RP + MCO, 4) Escalated + RP and 5) Escalated + RP + MCO. Finally, plan deliverability for all plans was assessed using MapCheck, modulation factor (MF) and MLC average leaf pair opening (ALPO).
Results Dose escalated (Group 5) plans offered significantly superior PTV_65 and GTV coverage (p<0.05) at particular dose metrics compared to the original (Group 1) plans (D95%, D2%). We found no significant difference between these groups for PTV_54 coverage for D95% (p=0.87) and D2% (p=0.09). Also, escalating the GTV dose did not significantly increase the OARs pertinent to this study; mean laryngeal (p=0.51), contralateral- (p=0.14) and ipsilateral- (p=0.11) parotid doses between these groups, seen in Table 1. On average, the overall hotspot increased from 108.6% to 128.4% for Group 5 resulting in sharper dose gradients around the target volumes affording equivalent OAR sparing. We found that Group 5 and Group 1 plans were clinically comparable in terms of plan deliverability with pre-treatment QA MapCheck results recorded at 3%/3mm. Also, the MF and ALPO for group 5 (0.48; 3.5) compared to group 1 (0.49; 3.1) further proved comparable plan deliverability.
8
Poster Presentation: Dr Laura Grocutt
28
Conclusions This planning feasibility study exploring RP combined with MCO has enabled the dose to the GTV to be escalated without significantly increasing pertinent OARs. As evidence showing that recurrences most often occur in the GTV is growing, dose escalation has the potential to treat high risk patients more effectively in the first instance and is likely to be safe due to comparable OAR doses currently administered.
Poster Presentation: Caitlin Reilly
29
Characterisation of 99mTc-Tektrotyd Physiological and Tumour Uptake using Standardised Uptake Values
Caitlin Reilly1, Alastair Gemmell2, Alice Nicol1
1. Dept of Nuclear Medicine, Queen Elizabeth University Hospital, Glasgow 2. Dept of Nuclear Medicine and PET, Gartnavel General Hospital, Glasgow
Background To investigate and determine standardised uptake values (SUVs) from 99mTc-Tektrotyd (99mTc-HYNIC-TOC) SPECT/CT imaging. 99mTc-Tektrotyd specifically binds to somatostatin receptors and is used clinically to localise neuroendocrine tumours and potential metastases. Quantification of 99mTc-Tektrotyd uptake could be useful as an adjunct to visual assessment and for monitoring disease progression or response to treatment. SUVs will be established in organs with normal physiological uptake and areas of tumour uptake to allow comparison.
Materials and Methods Patients referred for 99mTc-Tektrotyd imaging were retrospectively analysed. SPECT/CT imaging was performed 4 hours post injection on a Siemens Intevo16 SPECT/CT system (Siemens, Germany). Siemens xQuant software was utilised to produce absolute quantification values (SUVs). Volumes of interests (VOIs) in areas of normal liver, normal spleen, liver metastases and lung lesions were produced using Hermes Medical software (Hermes Medical Solutions, Sweden) and categorised from the Radiology report.
Key Results Preliminary results showed average SUVmax ± standard deviation to be 6.4 ± 1.8 in normal liver (n=5), 28.6 ± 3.5 in normal spleen (n=7), 14.7 ± 5.7 in liver metastases (n=2) and 22.8 ± 15.7 in lung lesions (n=2). This work will be extended further to include analysis of more normal organs and tumour uptake. However these initial SUVmax results show good differentiation between uptake in normal liver and liver metastases, and correspond with reported SUVmax values from Ga68-labelled somatostatin receptor radiopharmaceuticals.
Conclusion This investigation has demonstrated a methodology for determining SUVs from 99mTc-Tektrotyd SPECT/CT images which could aid visual interpretation, potentially be useful for monitoring disease progression and response to treatment.
9
Poster Presentation: Daniela Teixeira Macarico
30
Audit of V/Q SPECT Ventilation to Perfusion Count Rate Ratios using 99mTc - Technegas/ 99mTc-MAA
Gribben, D.(1); Teixeira Maçarico, D. (1); Laurins, C.(1); Nicol, A.(1)
(1) NHS Greater Glasgow and Clyde – Queen Elizabeth University Hospital, New Victoria Hospital and Institute of Neurological Sciences
Background V/Q SPECT scans using sequential 99mTcTechnegas/99mTc-MAA are performed for the assessment of pulmonary embolus. The target ratio of Perfusion:Ventilation countrate should be greater than 4:1 but not always achieved due to patient compliance . An audit of Perfusion and Ventilation count rate ratios (Q:V) in V/Q scans before and after a change in the local DRL for 99mTc-MAA was performed.
Materials and Methods An audit was performed in 22 patients and the ratios Q:V were compared using the count rate from the PPM and the first projection (40/20MBq 99mTc Technegas, 185MBq/80MBq 99mTc-MAA, reduced for pregnancy or Pulmonary Hypertension). Following this, the 99mTc-MAA DRL was increased to match the ARSAC value (200MBq/100MBq) and another 22 patients were audited.
Key Results At our centre, most V/Q scans are performed using reduced activity (73% in this study) due to e.g. pregnancy. For the original DRL the Q:V ratio had an average of 5.0±1.4 with a minimum of 2.3 and maximum of 8.2. Four (18%) of the patients had a ratio less than 4. Using revised DRL, the average Q:V ratio was 6.1±1.2 (minimum=3.3 and maximum=8.2) and two (9%) of the patients had a ratio less than 4.
Conclusion Several cases were observed with Q:V ratio under 4. This may occur due to patient related factors and should be flagged to the staff reporting. The department decided to increase the 99mTc-MAA DRL and considerably fewer cases with low ratios were obtained. Therefore, this audit showed the benefit of increasing the 99mTc-MAA DRL for the scan.
10
Poster Presentation: Dr Alice Nicol
31
123I FP-CIT Image Characteristics in Parkinson’s Disease and Lewy Body Dementia
Nicol A, Spratt A, Jampana R, Grosset D, Jackson E, Sheridan M
Background 123I FP-CIT imaging of striatal dopaminergic neuron terminals is used in the diagnostic pathway of Parkinson’s Disease (PD) and Lewy Body dementia (DLB). 123I FP-CIT scans of a series of consecutive patients with PD or DLB who had 123I FP-CIT imaging in their diagnostic phase were assessed. The frequency and characteristics of the patterns of 123I FP-CIT uptake were determined. Materials and Methods Patients were followed up clinically and PD or DLB subsequently confirmed. Clinical follow up was also performed on a group of subjects subsequently determined to have neither PD nor DLB. The 123I FP-CIT scan appearances were assessed visually (normal, anterior-posterior gradient or balanced loss) and frequencies compared for the PD and DLB groups. Putamen-caudate ratios were calculated for the scans classified as normal, anterior-posterior gradient and balanced loss.
Key Results Subjects with PD (n=19, 14 M, 5 F, mean age 69 (SD 9.3)) had an anterior-posterior gradient pattern in 95% of cases, with the remaining scan a balanced loss. Subjects with DLB (n=13, 9 M, 4 F, mean age 77 (5.5)) had an anterior-posterior gradient in 46% of cases and a balanced loss in 54% of cases. The frequency of scan patterns was different for the PD and DLB groups (chi squared test of homogeneity, p<0.01). All the subjects subsequently determined to have neither PD nor DLB (n=22) had a normal 123I FP-CIT scan. The putamen-caudate ratios of the striata in the normal (n=44, mean 0.94, SD 0.07), anterior-posterior gradient (n=48, mean 0.75, SD 0.10) and balanced loss (n=16, mean 0.87, SD 0.08) groups were significantly different (ANOVA, p<0.01)
Conclusion The frequency of 123I FP-CIT scan patterns differs between PD and DLB. Knowledge of the prevalence of patterns of dopaminergic loss is critically important when clinically evaluating scans. N Anterior-posterior gradient
(%) Balanced loss (%)
Parkinsons Disease 19 18 (95) 1 (5) Lewy Body Dementia 13 6 (46) 7 (54)
11
Poster Presentation: Gary Hilland
32
Serum creatinine measurement as a predictor for single sample GFR using 99mTc-DTPA
Gary Hilland1, Ana Matos1, Dr Caroline Findlay1
1Dept of Nuclear Medicine, Gartnavel General Hospital, NHS Greater Glasgow and Clyde.
Background Radionuclide measured Glomerular Filtration Rate (mGFR) assessment using 99mTc-DTPA (Diethylenetriamine Pentaacetic Acid) is widely used in Nuclear Medicine for patient’s pre-nephrotoxic chemotherapy or assessment of potential live kidney donors (PLKD). British Nuclear Medicine Society (BNMS) guidelines published in 2004 recommended using a 4-sample slope intercept GFR protocol (SI-GFR).(1) However updated BNMS guidelines published in 2018 recommend a single sample GFR measurement (SS-GFR) for patients without ascites, oedema or other expanded body space. (2) The recommended single sample time should be based on the best available estimate of body surface area normalised GFR. One such measurement is the estimated GFR (eGFR) based on serum creatinine concentration. The purpose of this audit was to compare SI-GFR and the SS-GFR measurements to aid confidence in transitioning to a SS-GFR method. We also wished to look at the validity of using eGFR as a single sample time predictor.
Materials and Methods Using 4-sample SI-GFR measurements, the equivalent SS-GFR was calculated using the single sample time point identified in the guidelines. The patient’s most recent eGFR measurement was used to identify which of the 4 blood samples would be the SS equivalent. eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Creatinine 2009 equation. (3, 4)
Figure 1: CKD-EPI Creatinine 2009 Equation
Key Results Eighty nine 99mTc-DTPA SI-GFR patients were retrospectively reviewed. The eighty nine patients comprised of 63 pre-chemotherapy assessment, 25 PLKD patients and 1 other with an average eGFR of 94.4 ± 25.3 mL/min/1.73m2. The average SI-GFR and SS-GFRs were 86.4 ± 23.5 and 86.8 ± 22.2 mL/min/1.73m2 respectively. Time between eGFR and mGFR was 22.8 ± 31.2 days. Using the non-parametric Wilcoxon Signed Rank test, recommended single sample times across all eGFRs values demonstrated no statistically significance between SI-GFR and SS-GFR (p=0.70, N=89) with an absolute average difference between the SI-GFR and SS-GFR of 2.01 ± 1.6 mL/min/1.73m2. Further investigation revealed that there were no significant differences between the SI-GFR and SS-GFR for eGFRs >100 mL/min/1.73m2 (p=0.09, N=42) and eGFRs between 70-100 mL/min/1.73m2 (p=0.12, N=36). However, there was significant differences for eGFRs <70 mL/min/1.73m2 (p=0.006, N=11).
12
Poster Presentation: Gary Hilland
33
Figure 2: Comparing GFR methods by sample time
Conclusion Preliminary findings using eGFR to determine single sample times for 99mTc-DTPA mGFRs gave mixed results. As anticipated eGFR is not a good predictor of SS-GFR or SI-GFR measurements. With regards to mGFR methods, SS-GFRs taken at 2 and 3 hours do correlate with SI-GFRs. However results from this cohort of patients demonstrate that SS-GFRs taken at 4 and 6 hours were different from the SI-GFR measurement. Further work would be needed to expand on the results for GFRs < 70 mL/min/1.73m2. It would also be useful to explore whether there is improved accordance between the two methods if an eGFR measurement was performed on the morning of the mGFR procedure to assist the SS-GFR time point identification. Finally the clinical significance of any discrepancies between SS and SI GFRs will also be of relevance during this transition period.
References (1) Fleming, J., Zivanovic M., Blake G., Burniston M., Cosgriff P. (2004) Guidelines for the
measurement of glomerular filtration rate using plasma sampling. British Nuclear Medicine Society. Nucl Med Commun [Internet]. 25(8):759–69.
(2) Burniston, M. (2018). Clinical Guideline for the measurement of glomerular filtration rate (GFR) using plasma sampling. British Nuclear Medicine Society.
(3) Levey, A. S., Stevens, L. A., Schmid, C. H., Zhang, Y. L., Iii, A. F. C., Feldman, H. I., …
Greene, T. (2014). A New Equation to Estimate Glomerular Filtration Rate. Annals of Internal
Medicine, 150, 604–612.
(4) Florkowski, C. M., & Chew-Harris, J. S. C. (2011). Methods of estimating GFR - Different
equations including CKD-EPI. Clinical Biochemist Reviews, 32(2), 75–79.
0.0
20.0
40.0
60.0
80.0
100.0
120.0
2 3 4 6
GFR
(m
L/m
in/1
.73m
2)
Sample Time (Hrs)
Comparing GFR methods by sample time
eGFR SS-GFR SI-GFR
Poster Presentation: Iain Kerr
34
Referral Rates and Overall Survival of Patients Receiving Ra223 Therapy for mCRCP at the Beatson West of Scotland Cancer Centre
I. Kerr, G. Buchanan, Dr C. Brown, Dr C. Findlay
NHS Greater Glasgow and Clyde
Background In May 2016, the Beatson Oncology Centre (BOC) opened a Ra223 therapy service treating mCRPC patients in the West of Scotland. This catchment area includes referrals from six Health Boards, and a population of 2.8M. The aim of this work was to review the referral patterns and the outcome of patients in the three years since the service was established.
Materials and Methods The date of patient referrals to the service were audited to establish any trends in patient throughput. The Overall Survival (OS) of patients that completed all six cycles of Ra223 were compared with published data from the ALSYMPCA trial [1].
Key Results A total of 186 patients were referred between May 2016 and August 2019. The audit of patient treatments revealed an intial referral rate in the first six months (8.3 ± 2.5 per month) which was higher compared to the overall mean of the data (4.6 ± 1.0 per month). This higher rate corresponds to a backlog of patients waiting for the service to open. As these patients were more likely to have progressed while waiting for treatment, they were more symptomatic and, therefore, less patients completed all six fractions (40% compared to 54.1%).
Of note, following the Pharmacovigilance Risk Assessment Committee (PRAC) guidance [2] which relegated Ra223 to third line treatment in 13 July 2018, from September 2018 onwards, the referral rate has more than halved to 1.8 ± 0.5 per month. Of those patients completing all six fractions, 52 out of 94 patients (55.3%) are now deceased with mean OS of 9.7 months. The mean OS for the first cohort of patients however was 3.9 (range 1.1-6.4) months with the following patients’ mean OS being 10.8 (range 2.2-26.3) months. The remaining 42 patients are still alive following six cycles of treatment, and aren’t included in this OS analysis.
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Poster Presentation: Iain Kerr
35
The OS is less than that demonstrated by the ALSYMPCA clinical trial, which reported 14.9 months. It is likely that lower OS locally is due to less stringent inclusion criteria for clinical patients compared with ALSYMPCA clinical trial patients. This is particularly evident in the first cohort of more symptomatic patients that were treated when the service first launched who show a markedly reduced mean OS to that of later patients.
Locally only, 55% of patients completed all six fractions, whereas in the ALSYMPCA trial 63% completed the full course of six injections. Again, this difference is likely to be due to less stringent inclusion criteria locally with a singificant number of patients with disease progression while waiting for the service to commence.
Conclusion Due to less stringent referral criteria clinically and patients who progressed while waiting for the service to open, patients completing all six cycles of Ra223 therapy showed a lower OS compared to that reported by the ALSYMPCA clinical trial. Patients that are still alive were not included in the OS analysis. The number of patients being referred to the service has been significantly impacted by the new PRAC guidance. The overall survival of this new cohort of patients has not yet been evaluated.
References
[1] Parker, C. et. al. 2013. Alpha Emitter Radium-223 and Survival in Metastatic Prostate Cancer. N Engl J Med 2013;369:213-23 [2] EMA restricts use of prostate cancer medicine Xofigo https://www.ema.europa.eu/en/medicines/human/referrals/xofigo
Poster Presentation: Hugh Wallace
36
Preliminary Evaluation of Wholebody Quantitative 123I-MIBG SPECT/CT in Neuroblastoma
HJ Wallace1,4, MS Bradnam1,4, AA Bolster1,4 JE Foster1,4,
A Watt2, G Irwin2,4 D Murphy3, M Ronghe3, J Sastry3,4
1 Department of Clinical Physics and Bioengineering, 2 Paediatric Radiology, 3 Paediatric Oncology, NHS Greater Glasgow and Clyde.
4College of Medical, Veterinary and Life Sciences, University of Glasgow.
Background We present an audit of wholebody quantified 123I-metaiodobenzylguanidine (123I-MIBG) SPECT/CT in Neuroblastoma. The purpose was to report on the level of CT exposure achievable using wholebody SPECT/CT and to assess the viability of physiological liver uptake as a reference for normalisation of SUV between patients.
Materials and Methods Wholebody 123I-MIBG SPECT/CT was performed under general anaesthetic in 7 paediatric patients (14 scans) with confirmed Neuroblastoma and negative abdominal MRI for liver metastases. 6 patients (13 scans) were imaged from head to ankle (3x SPECT fields of view) and the remaining patient scan imaged from head to mid-thigh (2x SPECT FoVs). 4 patients had repeat images within the audit period. All images were acquired with a Siemens Intevo 16 SPECT/CT scanner using an optimised low-dose CT protocol developed using an anthropomorphic phantom. Hermes Medical SUV SPECT was used to reconstruct each wholebody SPECT acquisition quantitatively. A 3cm diameter spherical Volume of Interest (VOI) was placed in the upper right lobe of liver in each image. The mean and standard deviation of SUV within each VOI was recorded and used to assess inter-patient variability (first scan in the series per patient) and intra-patient variability (serial scans in the same patient).
Key Results The mean dose-length product (DLP) for head-ankle scans was 28.6mGycm, and the mean DLP per SPECT field of view was 9.54 mGycm. These figures showed good agreement with CT dosimetric modelling undertaken with the imPACT dose calculator. Based on these figures, the additional effective dose from CT in a 5 year old patient was estimated at 0.4 mSv for a head to mid-thigh image and 0.6 mSv for a head to ankle image. Both of these doses are less than 10% of the estimated exposure from an 123I-MIBG scan in a 5 year old patient. The mean SUV value for liver VOIs across all patients was 1.9 ± 0.6 (mean ± standard deviation). The coefficient of variation (CoV) within each liver VOI was consistent across the cohort (range: 10-15%). However the CoV between serial images was highly variable (range: 7-28%) with liver uptake appearing elevated immediately following treatment. In the worst case, the variability between serial patient images was equivalent to the variability between patients (standard deviations of 0.5 vs. 0.6 SUV respectively).
Conclusion With a modelled dose burden of less than 10% of the nuclear medicine exposure, the optimised low-dose wholebody SPECT/CT protocol is sufficiently low-dose for multiple repeat scans of Neuroblastoma throughout treatment. However for patients older than five years of age increased CT parameters are required to avoid artefacts. The variability of liver SUV measured between serial patient images may indicate that the liver is a poor physiological reference tissue for MIBG in Neuroblastoma. In patients undergoing serial scans throughout the treatment pathway, liver uptake appeared relatively increased immediately following chemotherapy or radiotherapy compared to scans several months post-treatment. Follow up work is planned to further investigate this liver variability and to exclude any additional technical factors.
14
Poster Presentation: Kirsty Jones
37
Figure 1 - Baseline LVEF vs baseline LVEF
Radionuclide Ventriculography Phase Analysis for Risk Stratification of Patients Undergoing Cardiotoxic Cancer Therapy
K.A Jones1,2, A.D Small1,3, C.A. Paterson1,2, D.J. Hamilton1,2, N.E.R. Goodfield1
1Dept of Nuclear Cardiology, Glasgow Royal Infirmary 2 School of Physics & Astronomy, University of Glasgow
3School of Medicine, Dentistry & Nursing, University of Glasgow
Background Accurate diagnostic tools to identify patients at risk of cancer therapy related cardiac dysfunction (CTRCD) are critical. CTRCD has become one of the main causes of morbidity and mortality in cancer survivors. Trastuzumab (Herceptin) is one example of cardiotoxic cancer treatment. It targets the epidermal growth factor and has been proven to improve life expectancy for breast cancer patients, but it is also known to be cardiotoxic. Approximate Entropy (ApEn) is a regularity statistic that quantifies unpredictability of fluctuations in data. It has not previously been widely investigated for assessing ventricular contraction. The aim of this work is to determine if ApEn calculated from baseline RNVG phase images can predict which patients are at a higher risk of CTRCD.
Materials and Methods Phase analysis was retrospectively carried out on sequentially acquired baseline RNVG studies of 177 breast cancer patients before they received Trastuzumab therapy. Using in-house R code, ApEn was calculated from the baseline RNVG phase images. Patients were split into groups based on the maximum LVEF decline during therapy.
Key Results 95 patients had no significant drop (< 10%) in LVEF, 71 patients showed a drop of more than 10% while maintaining a normal LVEF (> 50%), 11 patients were found to have a drop in LVEF of more than 10% to below 50%. A significant difference (p <0.05) in ApEn was found between the group that had an LVEF decline of more than 10% to below 50% and the other two groups.
Conclusion Patients with a high LVEF and low ApEn at their baseline RNVG are more likely to maintain a normal LVEF during therapy (Figure 1).This may help identify those at highest risk of CTRCD and allow
commencement of protective therapy and more focussed follow up.
15
Poster Presentation: Jennifer McCormick
38
DaTQUANT: Beyond the Scatter-gram A Neural Network add-on to classify DaT images
Jennifer McCormick
Dept of Nuclear Medicine, Medical Physics, Aberdeen Royal Infirmary, NHS Grampian
Background Ambiguous cases of suspected Parkinson’s disease and Lewy body dementia are often referred for imaging to confirm diagnosis and guide patient treatment. DaTQUANT™ generates a range of semi quantitative values representing the DaT (specific binding ratios (SBR)) uptake in the caudate and putamen). It can also compare the relationship between these values in an individual, to a well defined cohort of normal controls. In this study neural networks (NN) were developed to classify DaT images into positive or negative using these values; the classification gold standard was the radiological interpretation by an expert observer. The NNs were developed separately using two reconstruction approaches and their performance compared. Additional demographic data was introduced into the data sets to assess the discriminatory value of age, gender and referral group (Parkinson or Lewy Body Dementia).
Materials and Methods Using the DaTQUANTTM tool, data was extracted from 61 DaT datasets (the discovery set) and used to define a single layer perceptron NN. A further collection of 60 more datasets was used to validate the NN. This was repeated for both reconstructions (default DaTQUANT™ NC OSEM and Siemens Flash3D AC). The demographic measures were introduced separately and in combination and the process was repeated. Performance of all the NNs was quantified using the AUC ROC approach. Each process was repeated six times randomly assigning each patient dataset to either the discovery or validation set.
Key Results Using the default DaTQUANT™ OSEM reconstruction the imaging measures produced an AUC of 0.930 (StDev 0.008). This was significantly improved by including the referral group in the NN: AUC of 0.945 (0.010). Using the Flash3D data the AUC was calculated to be 0.922 (0.004). The addition of gender and referral type in the NN improved the performance to 0.942 (0.010). There were no significant differences found between the AUC ROC of the Flash3D and default DaTQUANT™ reconstructions when using the same demographic measures.
Conclusion The weaknesses of this study were the single site used and the expert observer as the gold standard, however, the approach shows potential to assist diagnosis and patient classification. No significant differences were found between the AUC ROC potential diagnostic ability of the reconstruction techniques, despite the significant differences in image contrast and SBR values.
16
Poster Presentation: Jennifer Summersgill
39
Dose Optimisation of F18-FDG in PET for patients with weight less than 67 kg
Jennifer Summersgill1 1Dept of Nuclear Medicine, Ninewells Hospital, NHS Tayside
Background Positron Emission Tomography (PET) has shown to be an important image modality for in-vivo quantitative measures of biochemical, physiological or pharmalogical processes. F18-FDG plays a major role in oncology aiding in the initial disease diagnosis, disease staging and for assessing treatment response. In NHS Tayside the activity administered to the patient is based off the patient weight as 3MBq/kg. However, if the weight of the patient falls below 67 kg they will be administered a minimum dose of 200 MBq irrespective of weight. This value has little evidence as to why it was chosen, this project aims to look into whether the activity can be optimised for patients of weight < 67 kg or to provide evidence for using 200 MBq as the minimum activity. Currently for each patient scan the PET scanner provides 2 reconstructions; OSEM and QClear. The Ordered Subsets expectation Maximisation (OSEM) algorithm works by finding the image that gives the maximum likelihood of producing data that equals that collected from the PET scanner. One drawback to this algorithm is the as the number of iterations increase the noise in the image grows. Therefore, the algorithm is generally stopped after 2-4 iterations to minimise the amount of noise. QClear is a new algorithm that came when the new scanner was installed. This is also an iterative reconstruction algorithm however it contains an additional term in the objective function. This term increases as the image noise increases, reducing the objective function and steering the algorithm away from noisier images. QClear has the advantage that the image can run to full convergence whilst suppressing background image noise and providing superior image quality, shown in Figure 2.
In NHS Tayside the clinicians currently report from the QClear reconstruction. This project also looked to compare these two algorithms and to confirm that QClear is the preferred reconstruction.
Materials and Methods Six patients were selected who had had a whole-body PET scan this year with a weight of 67 kg or less Two additional sets of images were created for each patient that simulated a lower administered activity. To simulate this the time per bed was shortened. Each patient ended up with four reconstructions; OSEM, QClear - 200 MBq, QClear - 3 MBq/kg, QClear- 2.5 MBq/kg. All images were anonymised and positioned so all four reconstructions were on the same display as shown in Figure 3.
17
Poster Presentation: Jennifer Summersgill
40
Key Results The feedback for the OSEM reconstructions were that they were less sharp and focal with more noise than the QClear ones and that they would be worried about missing small lesions. All four clinicians said they would be happy reporting from all three of the QClear reconstructions and stated they found it difficult to see the difference between the three QClear reconstructions.
Conclusion This project has been very subjective in the clinician feedback as they were purely looking at the images qualitatively. They were not given any patient history and were not asked to produce a diagnosis based on Standardised Uptake Values (SUVs). However, this project has highlighted that lowering the patient dose in these patients does not greatly alter the image quality.
Poster Presentation: Dr Pauline Hall Barrientos
41
Evaluation of transplant renal vascular disease by 4D flow P Hall Barrientos1, A J Rankin2, G Roditi3, P B Mark2, K A Gillis2
1Department of Clinical Physics and Bioengeering, NHS Greater Glasgow and Clyde, UK 2Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK
3Department of Radiology, NHS Greater Glasgow and Clyde, UK
Background
Investigation for transplant renal artery stenosis can be challenging given that doppler ultrasound is highly user dependent and given the issues with both iodinated and gadolinium based contrast in renal impairment. We aimed to evaluate the use of 4D flow to measure parameters in renal transplant arteries.
Materials and Methods 4D flow data were acquired for the abdominal aorta, iliac and transplant renal arteries. Conventional 2D phase contrast magnetic resonance imaging slices were acquired along the aorta for native native kidneys, and ipsilateral iliac artery. Studies were performed on a 3 T Siemens Prisma with a body array coil and ECG gating. The sequences used were as follows: 4D flow WIP 785k: TR/TE 45.92/3.19 ms, spatial resolution 1.5 x 1.5 x 1.5 mm, flip angle = 7°, venc = 100 cm/s and 30-50 cm/s, ~20 cardiac phases, scan duration ~8 minutes. 2D: TR 51.9 ms, TE 5.1 ms, spatial resolution 0.8 x 0.8 x 5 mm, flip angle = 20°, venc 100 cm/s, ~30 cardiac phases, scan duration 9 s. 4D flow datasets were analysed using a work-in-progress package supplied by Siemens. 2D datasets were analysed using Argus by Siemens.
Key Results
5 participants were recruited: 4 patients with kidney transplants, and 1 healthy volunteer. Table 1 demonstrates the results of net flow and peak velocities with the renal artery. There were no significant differences between 2D and 4D net flow measurements (p=0.48, mean bias 0.8 ± 4 mL/s).
Conclusion Renal artery blood flow measured by 4D flow was variable, in both kidney transplant recipients and in the native kidneys of a healthy volunteer. Turbulent flow, suggestive of stenosis, was not identified in any of the participants. 4D flow allows measurement and visualisation of renal artery flow in transplant and native kidneys. Further studies are required to fully understand flow dynamics and normal range of renal artery velocities in native and transplant kidneys.
References 1. Markl, M., Frydrychowicz, A., Kozerke, S., Hope, M., & Wieben, O. (2012). 4D flow MRI. Journal of Magnetic Resonance Imaging, 36(5), 1015-1036.
Volunteer 1 Patient 1 Patient 2 Patient 3 Patient 4
Net flow (mL/s) L 2.7 R 3.7 2.3 13.2 5.3 7.4
Peak velocity (cm/s)
L 58 R 53 66 81 68 66
Area (mm2) L 11 R 16 9.2 43.7 25 75
18
Poster Presentation: Amy Morton
42
Optimisation of Functional Magnetic Resonance Imaging in Phantoms and Volunteers Using Simultaneous MultiSlice
Amy Katharine Morton1, Dr. Jennifer Macfarlane1
1Medical Physics, Ninewells Hospital, Dundee
Background Blood-Oxygen-Level Dependent (BOLD) imaging is a method used in fMRI to investigate the activity of regions of the brain by measuring the level of oxygen in the blood stream. It is used for a variety of different purposes, from pre-surgical clinical scans to highlight areas of specific function to plan a surgical route, to research studies trying to determine which parts of the brain are associated with
various tasks or decision making processes.
This project investigated the impact of parameters used in fMRI sequences on image quality. Concerns about distortion and signal dropout in fMRI data had been raised, and so specific sequences were optimised to rectify this. Additionally, a trial license of Simultaneous MultiSlice (SMS) was investigated as to whether this was worth investing in to aid with optimisation.
Materials and Methods Data were collected using a Siemens 3T Magnetom Prismafit MRI scanner and a 20 channel transmit-receive head coil. Phantom work looked at the signal dropout and signal-to-noise ratio (SNR). Repetition time (TR), echo time (TE) and flip angle were investigated, along with the effects of increased slice acceleration using SMS. These results were used to influence the volunteer acquisitions which focused on optimisation of the fMRI protocols used extensively in the past.
Key Results The phantom work showed areas of distortion were reduced by using a minimum TE value allowed by parallel imaging, as there was less time for distortion to develop. The optimal flip angle, the calculated Ernst angle, gave an increase in signal and hence SNR. When applying SMS, the increased slice acceleration allowed very low values of TR and therefore more EPI volumes. However, with higher slice acceleration, SNR was significantly reduced with artefacts present, increasing distortion. The volunteer work optimised two protocols using a combination of basic parameters and SMS. In both cases, the TE was reduced to a minimum value, reducing distortion. The TR was also reduced, allowing the number of EPI volumes to be increased and hence theoretically increasing the statistical strength of the functional analysis.
Conclusion Phantom data showed that minimum TE could reduce the distortion, and an optimal flip angle could be used to increase the overall signal. Both imaging protocols investigated by the volunteer work could be optimised without the use of SMS, so the purchase of the license for these purposes was not indicated.
References [1] B. Forster et. al. Functional magnetic resonance imaging: the basics of blood-oxygen-level dependent (BOLD) imaging. Canadian Association of Radiologists Journal, 49(5):320-9, 1998. [2] M. Barth et. al. Simultaneous multislice (SMS) imaging techniques. Magnetic Resonance in Medicine, 75(1):63-81, 2016.
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Poster Presentation: Christopher Taylor
43
Active Transmit/Receive Switching for Fast Field-Cycling MRI
Christopher Taylor1, Dr James Ross2 1Medical Physics Department, Ninewells Hospital, NHS Tayside
2Biomedical Physics, School of Medicine, Medical Science & Nutrition, University of Aberdeen
Background Fast Field-Cycling (FFC) MRI is a novel technology that offers more clinical information for pathology compared to conventional MRI [1]. However, like conventional MRI, the transmission of pulse sequences used for imaging relies on the RF system. This includes the use of a Transmit/Receive (T/R) switch, which isolates parts of the RF system during transmit and receive. Currently, passive T/R switches are used, which relies on the AC current from a RF pulse to switch between transmit and receive. However, the use of RF pulses limits their ability to provide high fidelity pulse shapes during transmission and directly impacts the slice profile of the scanner. One way this can be overcome is the use of an active T/R switch that is able to switch between transmit and receive using gating DC current. This project investigated the considerations and construction of an active T/R switch for use with the 0.2T whole-body FFC-MRI. The performance of the active T/R switch was directly compared with a passive T/R switch by means of slice profiles and SNR. The introduction of an active T/R switch requires sensitive electronics that are subject to damage in the presence of RF. This project also investigates methods of RF blocking for these components.
Materials and Methods
An active T/R switch was successfully constructed (Figure 1). The T/R switch performance was measured by observing the RF fidelity, measuring the slice profile and the image signal to noise ratio (SNR). These results were then compared to a previously used passive T/R switch.
Figure 1
Summary of methods: - The RF fidelity was measured using a search coil placed perpendicular to the B1 field of the RF coil. - The slice profile was obtained using a spin-echo pulse sequence with readout oriented along the slice direction. - SNR was obtained by using a knee coil with a flood phantom. Images were acquired using a spin-echo pulse
Key Results An Active T/R switch was successfully constructed for the FFC-MRI. The addition of the new T/R switch saw improved RF pulse shape fidelity and an improved slice profile. The Images produced with the use of the active T/R switch, resulted in 37% improvement in SNR.
Conclusion The active T/R switch was successfully constructed and offered improvements in slice profiles and SNR. A RF blocking component was also constructed providing suitable protection to the addition of RF sensitive components. The use of the active T/R switch has overall improved the performance of the 0.2 T whole-body FFC-MRI scanner.
References [1]Broche, L. M. et al. (2019) ‘A whole-body Fast Field-Cycling scanner for clinical molecular imaging studies’, Scientific Reports. Nature Publishing Group, 9(1)
20
Poster Presentation: George Bruce
44
The Effect of B1 Variation on T1 Estimates at 7 Tesla G.Bruce1,2, G.Keith1, S.Williams1, D.Porter1
1Imaging Centre of Excellence (ICE), Institute of Neuroscience and Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow; 2NHS Greater Glasgow and Clyde.
Introduction Tissue relaxation times for white matter, grey matter and cerebrospinal fluid (CSF) in the brain have been studied extensively at 1.5T and 3T. However, due to limited data for the corresponding values at 7T, there is still a need for investigation of these relaxation measurements, which will be useful clinically. As field strength increases, T1 values tend to get longer and T2 values shorter, and so relevant relaxometry information is required to optimise scan protocols for 7T. Alongside the known benefits offered by 7T MRI [1], come new challenges which are less prominent at lower field strengths, such as greater radiofrequency transmit (B1) field inhomogeneity. This preliminary study uses phantom measurements to investigate the impact of this B1 variation on T1 estimates derived from an optimised inversion recovery spin echo (IR-SE) scan protocol.
Methods
For this study, a MAGNETOM Terra 7T MRI scanner (Siemens Healthineers, Erlangen, Germany) was used with a head and shoulder phantom with an unknown, uniform T1 (40.3% water, 58.3% sucrose, 1.24% NaCl, 0.08% preservative conductivity 0.38 Sm-1, permittivity 49.8F Fm-1). The gold standard method for T1 relaxometry, an IR-SE sequence, was used [2]. The IR-SE signal can be
modelled using an exponential equation [3]. In this case, the signal model, 𝑆(𝑇𝐼) = 𝑎 + 𝑏𝑒−𝑇𝐼/𝑇1 was
used, where parameters a, b and T1, were estimated from the IR curve plotted using magnitude data for 6 inversion times (TI). The data were fitted to this model using a non-linear least squares fitting algorithm [3]. The model assumes that the TR >> T1 of interest. A nominal flip angle T1 map in vivo was created from multiple EPI sequences to investigate the effects of this B1 inhomogeneity.
Results Data from the IR-SE phantom scan, Figures 1(a) and 1(b) illustrate the impact of the B1 variation on the T1 estimate. The T1 estimate for this phantom within the nominal flip angle range 85° to 95° is 467 ± 7ms. However, the estimate obtained for a lower range, 55° to 65° reported a value of 481 ± 24ms. The T1 estimates for different flip angle ranges, with errorbars representing the SD for that range, is shown in Figure 1(c). The suggestion that the effects of B1 inhomogeneity at 7T on T1 mapping is significant was not validated by the nominal flip angle T1 map created using multiple EPI sequences.
Discussion & Conclusions Using a phantom with a uniform T1 value, it was not possible to obtain a uniform T1 estimate due to B1 field inhomogeneities. The large SDs for low flip angle ranges in Figure 1(c) indicate that T1 estimates from those regions are not reliable. Work is currently ongoing to obtain a T1 estimate which is more robust to B1 variation, through scan protocol optimisation and consideration of B1 field effects. Preliminary scan data acquired in vivo also indicate that the B1 inhomogeneities are a confounding factor, causing a variation in T1 estimates beyond the expected effects due to anatomical variation. Further in vivo studies will be carried out to provide reliable estimates of these relaxation times in brain tissues. Creating a nominal flip angle T1 map showed no significant difference in T1 estimate with B1 inhomogeneities and so further work is required to investigate the impact of this more thoroughly.
References [1] Kraff, Oliver, et al Journal of Magnetic Resonance Imaging 41.1 (2015): 13-33. [2] Paul S Tofts..In: Proc Int Soc Magn Reson Med. 2009, pp. 1–6 . [3] Jo ̈elle K Barral et al.. In:Magnetic resonance in medicine 64.4 (2010), pp. 1057–1067
Figure 1(a) The flip angle map for the Phantom. (b) A map of T1 estimate across the
phantom. (c) Mean T1 values at different flip angle ranges with standard deviation (SD).
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Poster Presentation: Eilidh Avison
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Acoustically Characterising Materials for Use in a Transcranial Ultrasound Phantom
1Avison E, 1Prosser J, 1Tarbuck A, 1Kerr P, 2Inglis S, 3Seton H
1Medical Physics, NHS Highland, UK 2Medical Physics, NHS Lothian, UK
3Medical Physics, University of Aberdeen, UK
Background The effective treatment of stroke is time critical and relies on differentiation between ischaemic and haemorrhagic strokes. Transcranial ultrasound can be used to identify stroke when CT is not available, with potential uses in telemedicine and in rural settings [1]. An acoustically equivalent head ultrasound phantom, with both brain and bone components, would be useful for training purposes and to further develop this method. Aim: to investigate and acoustically characterise potential materials for use in a head phantom.
Methods Potential brain- and bone-equivalent materials were identified, and several simple test phantoms made with jelly and psyllium husk powder were created to mimic haemorrhages in the brain. These were imaged with ultrasound. The speed of sound and acoustic attenuation of agar-based samples doped with different concentrations of aluminium oxide and silicon carbide powders, for brain-equivalence, and epoxy resin and Peopoly UV resin, for bone-equivalence, were measured using an acoustic macroscope.
Key Results The average speed of sound for all agar samples was 1555 m s-1, 2401.4 m s-1 for epoxy resin and 2399 m s-1 for Peopoly UV resin. Attenuation results can be seen in Figures 1 and 2. The speed of sound in agar, epoxy resin and Peopoly resin were within the clinical range of the tissues. The agar samples had some non-uniformity in attenuation values and, although they agreed well with liver, were low compared to brain. Both bone-equivalent samples had low attenuation compared to temporal bone.
Conclusion With further work, the chosen and tested materials show promise for use in transcranial ultrasound phantoms.
Key references [1] Eadie et al. “Remotely supported prehospital ultrasound: A feasibility study of real-time image transmission and expert guidance to aid diagnosis in remote and rural communities”. J Telemed Telecare. 2018 [2] Duck, Physical Properties of Tissue: A Comprehensive Reference Book 1990 [3] Bai et al., Design and Characterization of an Acoustically and Structurally Matched 3-D-Printed Model for Transcranial Ultrasound, J. Acoust. Soc. Am. 2012 [4] Pfaffenberger et al., Can a commercial diagnostic ultrasound device accelerate thrombolysis? An in vitro skull model, Stroke 2005 [5] Ammi et al., Characterization of ultrasound propagation through exvivo human temporal bone, Ultrasound Med Biol. 2008
Fig. 1: Agar attenuation coefficients from three samples of each concentration compared to brain
and liver attenuation data from [2].
Fig. 2: Bone equivalent attenuations compared to temporal bone experimental attenuation data from
[3-5].
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Poster Presentation: Craig Lees
46
A Comparison of Nomograms to Diagnose Bladder Outlet Obstruction in Women
Craig Lees1, Duncan Middleton2, Tom Waterhouse1, Lesley Hogg1
1Dept of Clinical Physics & Bioengineering, Royal Alexandra Hospital 2Dept of Clinical Physics & Bioengineering, Queen Elizabeth University Hospital
Background Although several definitions have been historically proposed, no universally accepted urodynamic criteria currently exists to diagnose the presence of bladder outlet obstruction (BOO) in female patients. Among the proposed criteria for defining BOO in women, nomograms based on maximum flow rate (Qmax) and detrusor pressure (Pdet) parameters have been developed by Blaivas and Groutz (2000) and, more recently, by Solomon and Greenwell (2018) as tools in the urodynamic investigation. Along with their nomogram, Solomon and Greenwell proposed a female bladder outlet obstruction index (BOOIf) defined as; Pdet@Qmax – (2.2)Qmax with the thresholds, BOOIf< 0 signifying a probability of
obstruction < 0.1, BOOIf> 5 signifying the probability of obstruction being 0.5 (“likely obstructed”) and BOOIf> 18, which was interpreted as “obstruction almost certain” with a probability > 0.9.
Materials and Methods A retrospective analysis of the urodynamic traces of 100 patients from the Queen Elizabeth University Hospital (QEUH) was conducted. Both the Blaivas-Groutz and Solomon-Greenwell nomograms were applied to the obtained results to compare the prevalence of BOO in the sample population as defined by both methods.
Key Results Comparison of the classification of BOO in the sample population using both methods was varied. All patients classified as unobstructed via the Blaivas-Groutz method (N=35) were found to have a BOOIf< 5 while all patients with BOOIf> 5 (N=23) were similarly classified with some degree of obstruction according to the Blaivas-Groutz criteria. An additional 42 patients were also evaluated with a BOOIf< 5 but classified as either mildly (N=37) or moderately (N=5) obstructed according to Blaivas-Groutz showing significant disagreement between both methods.
Conclusion Blaivas-Groutz criteria for diagnosing BOO in our sample indicated that 65% of patients in the sample population suffered from obstruction to some degree. Typical estimates of the prevalence off BOO in women range from 2.7% to 29% and so the Blaivas-Groutz diagnosis rate appears to be unrealistically high. The 23% of patients calculated to have a BOOIf> 5 is more in line with conservative estimations and as such, could possibly indicate that the Solomon-Greenwell method is the more diagnostically accurate method of the two. This disparity highlights the need for a better understanding of physiological parameters with which to diagnose BOO in female patients through pressure flow studies (PFS) alone without the need for additional, confirmative procedures.
References [1] Blaivas JG, Groutz A. Bladder outlet obstruction nomogram for women with lower urinary tract symptomatology. Neurourol Urodyn. 2000;19:553–564. [2] Solomon E, Yasmin H, Duffy M, et al. Developing and Validating a New Nomogram For Diagnosing Bladder Outlet Obstruction in Women. Neurourol Urodyn. 2018;37:368-378.
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Poster Presentation: Gabriel Reines March
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Registration of Pre-Operative Lung Cancer PET/CT Scans with Post-Operative Histopathology Maps
G. Reines March1,2, C. Dick3, S. Harrow4, R. Sayer1, X. Ju1, S. Marshall2
1Medical Devices Unit, West Glasgow ACH, NHS Greater Glasgow and Clyde, Glasgow 2Dept. of Electronic and Electrical Engineering, University of Strathclyde, Glasgow
3Clinical Pathology, Queen Elizabeth University Hospital, NHS Greater Glasgow and Clyde, Glasgow 4Thoracic Oncology, Beatson WoSCC, NHS Greater Glasgow and Clyde, Glasgow
Background There is currently insufficient data describing the cellular make-up of a tumour in relation to its functional imaging. This research project focuses on registering pre-operative PET/CT scans from lung cancer patients to their post-operative histology slides, enabling clinicians to draw spatial correlations between the tumour’s metabolic fingerprint and its actual histopathology map.
Materials and Methods Between January and June 2018, the research team identified and recruited 9 patients diagnosed with primary NSCLC and referred for radical lobectomy, across NHS Greater Glasgow and Clyde sites. Each participant was scanned in a combined PET/CT scanner prior to surgery, as per standard of care. The resected lobe was fixed in formalin for a minimum of 48 hours and injected with a 4% agar solution through the airways to stiffen the tissue and facilitate slicing. Once solid, the whole lobe was placed in a purpose-built slicing rig and dissected at regular 5-millimetre intervals. Each slice was photographed using a digital camera, then processed using a microtome and stained using immunohistochemistry (IHC) methods. Virtual 3D tumour models were reconstructed from the CT and gross pathology images and registered using a linear affine transformation algorithm in Matlab 2017b (The MathWorks Inc, US). Real CT data was subsequently deformed using the same transformation matrix to match the gross pathology cutting planes. Histology slides were also aligned to the block-face photographs by applying a non-linear registration algorithm, constrained by one-to-one correspondences between common landmarks (i.e. edges, vessels, airways) identified on both image datasets.
Key Results An average Dice similarity coefficient of 83% was obtained for the CT-to-pathology tumour model registration. Due to the quasi-spherical shape of most tumours, the orientation was found to be wrong in 3 cases, despite high overlapping scores. Therefore, the registration algorithm used considered fiducial markers located in and around the tumour (e.g. airways or vessels) to ensure correct orientation. The figure below shows a sample slice of a transformed CT volume (A,B) which is matched to its corresponding gross pathology photograph (C), with overlapped histopathology data.
Conclusion This proof-of-concept study has managed to spatially match pre-operative CT tumour data with its actual histopathology map, and we are in the process of extrapolating these results to 4D FDG PET data. This acquired knowledge shall provide an informed, targeted approach for future radiotherapy studies.
A
B C
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Poster Presentation: Clodagh Duffy
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A Review of Clinical Outcome Measures and Proposed Active Prosthetic Users’ Mobility Evaluation Tool Set (APUMET)
Clodagh Duffy 1,2, Michael Dolan2, Arjan Buis1
1 Biomedical Engineering Department, University of Strathclyde. 2 Southeast Mobility and Rehabilitation Technology Centre, Astley Ainslie Hospital.
Background In 2014 funding was allocated in Scotland to support provision of state of the art (SOTA) prosthetics to active lower limb prosthetic users meeting SOTA criteria. An earlier piece of work looked at case-based outcomes of 21 of these patients aged 52.2 ± 11.6 years, specifically transfemoral prosthetic users, who transitioned from a standard mechanical knee joint to a microprocessor-controlled prosthetic, using data collected both in a clinical environment and in the everyday setting with an activity sensor measuring continuously over one week [1]. These prostheses are intended for active patients and may in fact impair a less active patient’s walking due to a trade off between energy efficiency and stability. Therefore assessing prosthetic patient outcomes pre to post intervention is crucial in determining future patient interventions and directing review of practice with the aim of improving the service’s quality of care [2]. There is a lack of consensus regarding use of rehabilitation outcome measures, and the methods used to assess psychometric properties. The purpose of this study was to evaluate and review the use of outcome measures in clinical practice and to quantify their psychometric properties in order to define a toolset.
Materials and Methods Data was collected retrospectively from 12 outcome measures used by the gait analysis laboratory and prosthetics service which assess functional mobility, performance, comfort, gait deviation and balance both pre-intervention and 42 ± 14.5 weeks post-intervention. Correlations between outcome measures were measured using Pearson’s correlation coefficient and Spearman’s signed rank for non-normal data. A review of 36 existing outcome measures was also undertaken, taking into consideration factors such as reliability, validity, consistency, ceiling and floor effects and the minimal clinically important difference. These factors were considered, if available, and based on these a toolset was identified for active amputees.
Key Results Strong and significant (p<0.05) correlations were measured between the Locomotor Capability Index (LCI-5) and Activity-specific Balance Confidence (ABC) Scale scores (ρ=0.855) as well as Amputee Mobility Predictor (AMP) and LCI-5 (ρ=0.855), which measure balance and independent completion of activities. Strong and significant (p<0.05) correlations were also measured between the 10 metre timed walk test and L-Test of functional mobility (ρ=0.943) and the L-Test and 2 Minute Walk Test (2MWT) (ρ=-0.902), which are performance based measures. In contrast to this, non-significant (p>0.05) and weak (ρ<0.2) correlations existed between the Gait Profile Score (GPS) & Functional Assessment Questionnaire (FAQ) (ρ= -0.094) and the LCI-5 (ρ=-0.139) and FAQ, which are functional and self-assessment measures. Interestingly the same is seen between the Maximum Walking Distance & mean steps per day (ρ=0.145).
Conclusion A number of functional outcome measures exhibited strong and significant (p<0.05) correlations which may indicate possible redundancy of outcome measures and that the use of both measures may not be clinically useful, thus allowing the number used clinically to be reduced. Additionally, results suggest a disparity between functional changes and self-reported changes pre- to post- intervention, as well as changes measured at home and in clinic, suggesting that the patient’s own assessment of their rehabilitation does not always correlate to a similar observed or measured change. Thus changes in the self assessed and measured biomechanical function, performance and patient satisfaction should all be considered to provide a comprehensive picture. Additionally, the lack of correlation between the maximum walking distance assessed in clinic and the number of steps taken suggests that functional assessments within the hospital setting may not be
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Poster Presentation: Clodagh Duffy
49
the most accurate measure of performance. Assessing outcomes continuously in the home or community is rarely undertaken in patients with lower limb loss [3], however activity measurement is a valuable measure of real world benefit. With this information in mind the Active Prosthetic Users’ Mobility Evaluation Tool Set (APUMET) was created to capture all aspects of rehabilitation relevant to active amputees. Outcome measures include the Prosthetic Evaluation Questionnaire, 2 Minute Walk Time, Amputee Mobility Predictor, Gait Profile Score, Goal Attainment Scale, Activity Monitoring and Cognitive Demand Task Testing. This work provides evidence to shape the methods that can be utilised to assess future patient interventions.
References
[1] C. Duffy, "Comparison of function and mobility pre and post prescription of a microprocessor-controlled knee joint," in British Association of Prosthetics and Orthotics, Harrogate, 2019.
[2] G. Clarke, S. Conti, A. Wolters and A. Steventon, "Evaluating the impact of healthcare interventions using routine data," BMJ, vol. 365, pp. 1-7, 2019.
[3] B. Hafner and J. Sanders, "Considerations for development of sensing and monitoring tools to facilitate treatment and care of persons with lower limb loss," Journal of Rehabilitation Research and Development, vol. 51, no. 1, pp. 1-14, 2014.
Poster Presentation: Clodagh Duffy
50
Development of Tripod Walking Aids for an Adult with Spastic Diplegia Cerebral Palsy: from Concept to Delivery
Clodagh Duffy* and James Hollington
Southeast Mobility and Rehabilitation Technology (SMART) Centre, Astley Ainslie Hospital, Edinburgh. *Contact: [email protected]
Background The Custom Design Service at the SMART Centre exists to develop medical devices for patients with disabilities to support everyday functionality. A 35 year old male with Cerebral Palsy Diplegia was referred to the service by a physiotherapist concerned that an injury may occur while walking or completing a sit to stand manoeuvre with his walking sticks, as the sticks were consistently failing within months. It was determined that to allow the patient to maintain independence, an alternative solution was required.
Materials and Methods The process began with observation of the patient during normal use at the day centre he attended. This demonstrated that the patient supported the majority of his weight with the sticks. The patient highlighted the areas where failures tended to occur. The user specifications were identified and the design specification outlining the requirements for the device was created. The applicable standards were identified and existing devices on the market were researched; following this, design concepts were developed for the handle and legs. Designs were created with CAD software (Alibre) and mechanical loading under the most likely circumstances were simulated via FEA with a SimWise add on. FEA was undertaken by defining the materials and mesh size and adding boundary constraints. Forces applied were 200N, 900N and 300N forces added in the x, y and z directions respectively. These forces were chosen as representative forces applied when transferring 75% body weight to the sticks and were estimated on the patient’s mass of around 83kg. A safety factor of 1.5 was used and the forces were applied in the least favourable direction, as specified by BS EN 12182:2012. von Mises stress distribution is mapped and compared with the failure limit. Results indicated that design 2 was least suitable with high stress concentrations existing some areas. Some stresses were high enough to suggest there is a possible risk of failure. Designs 1 and 3 exhibited the lowest stresses (see figure 1). FEA was also carried out on handle designs which included a modified crutch handle, a steel handle and a steel reinforcement handle.
Figure 1. FEA Analysis undertaken on 4 designs. A modified Pugh’s design matrix with weighted scores was created to score four leg reinforcement and three handle designs. A clinical scientist independently scored the concepts and achieved the same result. Work instructions and CAD drawings were then submitted to the workshop for manufacture. The final design (see figure 2) involved welding inner steel vertical support tubes and triangular reinforcements to the legs to prevent high stresses due to bending moments at the joints, and removing the handle. A modified portion of a crutch handle was used to provide a base for the new
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Poster Presentation: Clodagh Duffy
51
handle. A new handle was made using steel tubing and covered with foam for comfort and grip. Physical testing was then carried out using the same forces used for FEA simulations. The sticks were placed on force plates and weights added to the handles to apply vertical force for at least 60 seconds. Horizontal forces were applied manually. Force magnitudes were then verified by taking force plate measurements in the x, y and z directions.
Figure 2. The final design
Key Results The physical testing and finite element analysis indicated that the design meets safety standards. During the delivery appointment the Goal Attainment Scale indicated a positive outcome as both goals set were achieved. The patient’s mother was also contacted two weeks post delivery. The patient was asked a few questions regarding satisfaction and the patient answered positively to each of these. The patient was also asked to rate satisfaction with the design from 1 – 10, 10 being very satisfied. The patient scored the design 10. He also expressed that he was “happy with the design” and is able to use the devices on his own without fear of breaking. The patient’s mother also expressed that these had increased his confidence while living independently.
Conclusion The design process was successful and resulted in devices which meet the design specification and are safe to use. The devices should act to enable the patient to live independently and to continue to exercise and access educational activity at his day centre.
Poster Presentation: Olivia Lala
52
Augmented Reality Enhanced Ophthalmic Diagnostics Olivia Lala, Dr Mario E Giardini, Dr Iain AT Livingstone
Department of Biomedical Engineering, University of Strathclyde
Background In slit-lamp imaging, an ophthalmologist can determine the size of eye structures using handheld measuring tools (e.g. callipers, rulers). This technique is both subjective and outdated, leading to unreliable and variable measurements even between clinical experts[1]. With the aim of achieving more reliable measurements, a virtual measuring system which complements slit-lamp use, was developed during the project.
Materials and Methods On a slit-lamp fitted with digital video cameras (fig. 1B), an augmented reality (AR) system was built in Python, using open source software. Virtual measuring tools were designed which could be overlaid on the slit-lamp image (figs. 1E-1H). These allowed for the size and orientation of an object on the eye to be defined. A 3D-printed, handheld manipulator (fig. 1C), displaying an Aruco marker ring, allowed the operator (fig. 1D) to prompt and control the virtual system.
Figure 1: Left: System set-up: A – patient; B – slit-lamp; C – handheld manipulator; and D –
operator. Right: Different virtual tools: E – circle tool (calculates size of circular object); F – ruler tool (calculates lengths of two axes); G – angle tool (defines angular orientation); and H – pointer tool
(indicates to area of interest).
Key Results To assess the accuracy of the different tools, objects were measured virtually and compared to the
real object measurements. The average differences in measured value were (0.120.07) mm,
(0.120.08) mm and (1.152.02) degrees for the circle, ruler and angle tool tests respectively. A noise
test was also carried out, comparing the difference between the true and virtual centre of the Aruco array. The test indicated instability between the real and virtual system, with offsets between the two centres.
Conclusions A novel AR measuring system was successfully developed. The different tools can define the orientation and size of a measured object through the slit-lamp. Noise tests identified instability in the system, with discordance between real and virtual points. Frame rate analysis highlighted the need for higher processing power. A preliminary use evaluation indicated the need for enhanced ergonomics. Future development of the project would see: the device undergo clinical trials to assess user validation; a more powerful processor being implemented to run the programme; and increased virtual functionalities to improve ergonomic constraints.
References
1. Parikh PC, Valikodath NG, Estopinal CB, Shtein RM, Sugar A, Niziol LM, Woodward MA. How
reliable are slit lamp biomicroscopy measurements of anterior segment
structures? Cornea 2017; 36(4).
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Poster Presentation: Rachel Jackson
53
Does Changing Virtual Reality Scenes Alter Walking Patterns of Healthy Adults?
Rachel Jackson1, Dr Andrew Kerr2, Dr Craig Childs2
1Dept of Clinical Physics & Bioengineering, Queen Elizabeth University Hospital 2Dept of Biomedical Engineering, University of Strathclyde
Background Virtual reality (VR) systems which incorporate gait training as a means of rehabilitation have had effective and promising outcomes in studies surrounding stroke, cerebral palsy, Parkinson's disease, and amputees1,2. A leading example is the Motek Computer Assisted Rehabilitation Environment (CAREN) system. Optic flow (OF) is known as the visual motion generated by the eye as a person moves. OF contains visual information which controls the direction and speed of walking. In the CAREN system, OF is integrated within a real-time feedback loop where the walking speed of the subject synchronises with the VR environment speed. The aim of the project was to investigate the effect of altering OF rate on spatiotemporal parameters, including stride length, stride time and cadence.
Materials and Methods Seven healthy participants were recruited following Ethics approval. Participant information including height, weight and lower body anthropomorphic data was collected and inputted into Vicon Nexus software. Markers were attached to anatomical landmarks according to the Plug-In-Gait lower body model to capture participant movement. Subjects were instructed to walk on a treadmill in a CAREN system environment at a comfortable walking speed which remained constant throughout. Participants were exposed to alterations of the visual field where OF rates were altered in a randomized order through eleven experimental conditions [Figure 1]. Data was captured using the Vicon Nexus system and spatiotemporal data at OF levels of -75%, 0%, and +100% were analysed on MATLAB software.
Figure 1. Different OF rates used in experimental conditions
Key Results Altering OF rates impacted gait patterns of healthy participants, although relationships were not found in each parameter across participants. In five out of seven participants, the highest cadence, or number of steps per minute, resulted from 0% condition which is the automated CAREN OF level. Stride length and stride time gave particularly sporadic results with no relationships present.
Conclusion Changing OF levels does have an effect on walking patterns in healthy individuals. The developed protocol will also be useful for University of Strathclyde’s future work developing rehabilitative gait training programmes for patients with stroke, Parkinson’s disease and lower limb prosthetics. Using the protocol to alter cadence may improve patient confidence in walking and enable clinicians to pinpoint areas where patients are struggling.
References 1. Fung, J., Richards, C.L., Malouin, F., McFadyen B.J., & Lamontagne, A. (2006) A treadmill and motion
coupled virtual reality system for gait training post-stroke. CyberPsychology and Behavior, 9, 157−162
2. Kruger, S. (2010) A virtual reality approach to gait training in service members with lower extremity amputations. Proc. 8th
Intl Conf. Disability, Virtual Reality & Associated Technologies.
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Poster Presentation: Sarah Francis
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A Virtual Reality Program for Upper Limb Rehabilitation Following Stroke
Sarah Francis, MEng MSc; Dr Wei Yao, PhD CEng MMechE (Supervisor) Dpt. of Biomedical Engineering, University of Strathclyde, Glasgow
Background Approximately 75% of the over 1.2 million stroke survivors who live in the UK experience weakness in their upper limbs. [1] Regular physiotherapy can significantly benefit recovery, but rehabilitation services in the NHS are struggling to meet the growing demand. [2] A virtual reality rehabilitation tool could allow stroke survivors to practice intensive, task specific physiotherapy at home, reducing the required number of clinical appointments. The aim of this project was to develop a clinically relevant VR program for rehabilitation of the upper limb following stroke, and to validate the ability of the virtual hand to replicate movement in real-time.
Design Following a literature review and a discussion with a physiotherapist, a list of design requirements for the rehabilitation program was developed. The program must include at least one clinically relevant rehabilitation activity which uses a virtual avatar to accurately recreate captured motion in real-time. The program also should include adjustable difficulty settings, give useful feedback to the user and be suitable to use at home. The program was designed in Unity (Unity Technologies, San Francisco, CA, v. 2019.1.5f1). It comprises of a main menu screen and three rehabilitation activities: the ‘Reach’ and ‘Pinch’ activities allow users to repetitively practice fundamental movements, while the ‘Virtual Kitchen’ provides a safe environment in which to practice activities of daily living. Each activity includes a virtual hand avatar3 which was programmed to replicate captured motion of a user’s hand, thumb and index finger in real time.
Key Results – Testing
Testing Methodology Optitrack’s V120:Trio camera was used for marker-based motion capture of phantom devices representing a hand, a thumb and an index finger. Motive: Tracker (Natural Point, Inc.) software was used to record the translation of the phantom hand in the x-y plane during the reach activity, and the rotation of the phantom thumb and finger around fixed z axes during the pinch activity. Simultaneously, the corresponding translation/rotation of the virtual hand, thumb and finger in Unity was recorded. To investigate the similarities between the phantom and virtual movements, the results were compared graphically and by calculating Pearson correlation coefficients.
A B C
Figure 1A: Reach activity – the user must reach with their hand to switch the lights from green to red, intermittingly returning to the centre of the screen. Figure 1B: Pinch activity – the user must repeatedly open and close their index finger and thumb to grasp the ball. Figure 1C: Kitchen activity – the user can interact with objects on the counter by reaching with their hand. The goal is to add milk to a bowl of cereal.
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Poster Presentation: Sarah Francis
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Key Results
Pearson correlation coefficients between the physical and virtual data were calculated at 0.917 and 0.904 for translations (x and y directions) of the hand (Fig. 2A), 0.915 for rotations of the thumb (Fig. 2B) and 0.764 for rotations of the finger (Fig. 2C).
Conclusion The results confirm the programs’ ability to accurately represent physical motion with a virtual avatar, and the program was able to meet the design requirements. Comparisons with similar designs in the literature demonstrate the potential of this program as a clinically effective rehabilitation tool. A random control clinical trial with stroke patients is necessary to confirm this prediction.
References [1] Stroke Association. (2018). State of the Nation - Stroke Statistics. [2] School of Population Health and Environmental Sciences King’s College London. (2019) Sentinel Stroke National Audit Programme (SSNAP) Clinical Audit - Annual Public Report. [3] GitHub - ololralph/vrsandboxgame: Open Source VR Sandbox Game Made With Unity. at <https://github.com/ololralph/vrsandboxgame> Date Accessed: [05/08/2019].
Figure 2A: Translation of the phantom (blue) and virtual (red) hand during the reach activity. Figure 2B: Rotation of the phantom (blue) and virtual (red) thumb during the pinch activity. Figure 2C: Rotation of the phantom (blue) and virtual (red) finger during the pinch activity.
A B C
Poster Presentation: Rebecca Stace
56
Raigmore Cath Lab: Tactics to Minimise Occupational Exposure Rebecca Stace1, Lera Köhler2, Andrew Hince3
1Pre-Registration Clinical Scientist, Dept of Medical Physics and Clinical Engineering, Raigmore Hospital, NHS Highland,
2Principal Clinical Scientist, Dept of Medical Physics and Clinical Engineering, Radiation Protection, Raigmore Hospital, NHS Highland,
3Consultant Clinical Scientist, Dept of Medical Physics and Clinical Engineering, Head of Radiation Protection, Raigmore Hospital, NHS Highland
Background Interventional cardiology procedures, involving exposure to ionising radiation from angiographic X-ray systems for diagnosis or treatment purposes, subject both the patient and operators to high doses [1]. With an increase in complex procedures, requiring longer exposure times, restricting staff doses has become more critical, requiring radiation safety measures to be reviewed – particularly to those areas of the body not protected by personal protective equipment (PPE) [1] [2]. Consequently, those staff present during a cardiac procedure should be made aware of “good” and “bad” practice with respect to radiation protection techniques. The current work hopes to provide recommendations on the most effective use of protection facilities available to staff working in the Cath Lab at Raigmore Hospital (NHS Highland). As such, the work is to serve as a learning aid by means of a poster for display in the Cath Lab.
Materials and Methods Three radiation detectors were employed to map the scatter levels (µGy/min), from a perspex phantom, at various staff positions during a simulated cardiac angiography procedure. Positions were defined for the collar and leg of a cardiologist in addition to the collar of a radiographer and scrub nurse. Measurements were obtained in the presence and absence of radiation shields (ceiling-mounted shield and table-suspended drape) for clinically relevant tube angulations.
Key Results The cardiologist benefits most from the protective radiation shields whereby the scatter-level at the position of the leg and collar are reduced by up to 100% and 90% respectively. For the straight PA view and RAO30 projection during fluoroscopy, the shielding provides suboptimal protection to the scrub nurse (less than 30% dose-rate reduction). In the presence of shielding, the CAUD30 LAO40 projection results in the maximum dose-rate to all staff groups. For PA acquisition, the scrub nurse position receives the highest dose-rate (3.7µGy/min). Across all tube angulations, the radiographer is in a position of relatively low scatter-level due to their increased distance from the patient. Minor adjustments in the ceiling-mounted shield has a large impact on scatter-level at the position of the cardiologist and scrub nurse. The gap between the patient table and bottom of ceiling-suspended shield could be creating a pathway for the scatter to the scrub nurse and cardiologist. It was found that when using additional shielding to close this gap, the greatest reduction in dose-rate (93%) was observed.
Conclusions Efforts should be focussed on a pragmatic response to help reduce radiation exposure to staff working within the Cath Lab. Of particular concern is the scrub nurse for which additional protective measures are encouraged to reduce dose-rates. The project supports the continued use of the radiation protection measures employed such as the ceiling-mounted shield and the table-suspended drape. Furthermore, it is hoped that the results obtained will encourage staff members to consider extra shielding in addition to protective eyewear – particularly for the CAUD30 LAO40 tube angulation.
References [1] C. J. Martin and D. G. Sutton, “Practical Radiation Protection in Healthcare, 2nd edition,” Oxford University Press, 2015. [2] D. Fornell, “Diagnostic and Interventional Cardiology: Defining the Cath Lab Workplace Radiation Safety Hazard,” [Online]. Available: http://www.dicardiology.com/content/blogs/. [Accessed April 2018].
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Scottish Trainee Event
Innovation Project Presentation Papers
7th DCPB Symposium
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Appendix: Scottish Trainee Event Schedule and Innovation Papers
Scottish Trainee Event
Imaging Centre of Excellence, Queen Elizabeth University Hospital Campus
Thursday 7th November 2019: 2 – 4pm
2.00 – 2.15 pm Tea, coffee & welcome (Chaired by Dr Doug Small)
2.15 – 2.35 pm Sarah Williams – Comparison of Left Ventricular Ejection Fractions between Anger and Solid-State Gamma Cameras
2.35 – 2.55 pm Lauren Urquhart – Impact on SPECT Reconstruction of Iterative Metal Artefact Reduction (iMAR)
2:55 – 3.15 pm Thomas McMullan – Long-Term Outcomes of Prostate Cancer Patients treated with Low Dose Rate Brachytherapy at Edinburgh Cancer Centre
3.15 – 3.35 pm Megara Srikaran – The use of Virtual Reality (VR) Technology to Improve Radiotherapy Information for Patients with Breast Cancer
3.35 – 3.50 pm Concluding remarks
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Comparison of Left Ventricular Ejection Fractions between Anger and Solid-State Gamma Cameras
Miss S.Williams 1,2, Miss K.Jones 2, Dr C.Paterson 2, Dr J.Robinson 2 , Dr N.Goodfield 2
1 Nuclear Medicine Department, Glasgow Royal Infirmary, Glasgow, UK 2 Nuclear Cardiology Department, Glasgow Royal Infirmary, Glasgow, UK
Abstract Introduction: In March 2019, GE’s dedicated cardiac solid-state gamma camera, the Discovery NM530C was installed at Nuclear Cardiology, Glasgow Royal Infirmary. A study was performed to compare the left ventricular ejection fraction (LVEF) measurements between the department’s existing Anger gamma camera, the IS2 and the solid-state camera, GE’s Discovery NM530C. The main objective was to compare the LVEF measurements between the acquired 2D planar data from IS2, the 2D reprojected planars from GE’s SPECT data and the 3D acquired SPECT for multi-gated blood pools.
Methods: An anonymised patient observer study involving 60 patients was carried out with three observers: two experienced clinical scientists and one trainee clinical scientist. This study involved observers analysing the acquired 2D planar and 2D reprojection images, obtaining LVEF measurements for both datasets, providing measures of inter-operator variation. A further assessment was performed to compare both 2D LVEF datasets with the 3D SPECT LVEF results using 4DM MUGA SPECT software for 28 patients and using Cedars-Sinai QBS software for 15 patients.
In addition to the clinical comparison using patient data, a prototype dynamic cardiac phantom was designed and manufactured to provide a comparison of both cameras with known LVEFs.
Results: Results indicate there is a strong correlation between all three LVEF measurements methods (2D planar/2D reprojected = 0.89, 2D planar/3D SPECT = 0.79, 2D reprojected/3D SPECT = 0.78). The difference between each method was not statistically significant (2D planar/2D reprojected = 0.46, 2D planar/3D SPECT = 0.55, 2D reprojected/3D SPECT data = 0.85). Further assessment is required to assess clinical significance of images with a variation greater than 5% as this would impact on the patient’s treatment. An additional evaluation of diagnostic quality of images, wall motion and increased background counts will be included in future work.
Background & Introduction Radionuclide ventriculography (RNVG) scans are used for blood pool imaging of the heart to observe the blood accumulation within the left and right ventricles and allow for an evaluation of cardiac function. The scan is performed using in vivo labelling of red blood cells (RBCs) by administering pyrophosphate (PYP) 20 minutes before administration of 99mTc-pertechnetate. The radiotracer labelled RBCs allow for imaging of the blood using a gamma camera. Analysis of these images provides an assessment of the left ventricular ejection fraction, wall motion and phase analysis.
At Nuclear Cardiology in Glasgow Royal Infirmary, there are two cardiac dedicated gamma cameras, the IS2 which is an anger technology gamma camera and the Discovery NM530c, a solid-state camera. The main difference between the solid-state and the conventional anger technology gamma camera is the use of Cadmium Zinc Telluride (CZT) [1] (GE Healthcare, 2019). CZT is a semiconductor which provides a direct conversion between the gamma photon and electrical signal for image generation, eliminating the need for photomultiplier tubes (PMTs) and reducing the need for collimation, resulting in improved sensitivity. As a photon is incident on the crystal lattice, charge pairs are produced and detected between a cathode and anode. As the electronics are compact, the anode is only millimetres from photon detection which results in improved resolution.
The Discovery NM530c uses multi-pinhole, angled collimator technology with a 3 by 9 configuration as shown in figure 1 and has a multiple detector array of pixelated CZT. The detectors and pinhole collimators are positioned towards a focal point to optimise cardiac imaging as shown in figure 2 and this increases the proximity to the heart [2] (Gimelli, A, 2010). Each individual detector has its own processing unit and applied corrections such as spatial linearity correction to further improve image quality and detector configuration [3] (Erik Mattsson, 2013).
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This project was carried out as part of the Scottish Medical Physics training scheme to fulfil the requirements for the innovative project and aimed to compare Nuclear Cardiology’s Anger technology and solid-state gamma cameras for RNVGs. An investigation was carried out to assess the possibility of using a 3D SPECT data reprojection technique. This would provide 2D images of the GE SPECT acquisition whilst transitioning from acquired planar to acquired SPECT data for RNVGs. The main objective of this project was to compare the LVEF measurements for the 2D planar, 2D reprojected planar and 3D SPECT data for a dataset of 60 patients. Finally, to provide a fair comparison between the two cameras, a bespoke dynamic cardiac ventricle phantom was designed and manufactured to have known ventricular ejection fractions, allowing for a comparison between the two cameras.
Methods Following the installation of GE’s Discovery NM530C, all patients attending for an RNVG scan received a 2D planar image acquisition on the IS2 according to the department’s standard protocol. This protocol involves acquiring an image at the angle of best separation and then a 10-minute acquisition at a left oblique angle, the 70 LAO. The patient then underwent additional imaging on the NM530C, acquiring a five minute 3D SPECT acquisition. The planar and SPECT data was acquired in list mode with gating of the patient’s electrocardiograph (ECG). Using an application on GE’s Xeleris workstation, all of the 3D SPECT images were reprojected into 2D multigated planar views with the operator deciding the angle of best separation on the short axis view. This resulted in a dataset of 60 patients that had received RNVG imaging on both cameras. The groups of patients included in this project are those that attended an RNVG for a Thallium stress test, LVEF assessment or had been prescribed Herceptin, a cardiotoxic drug, as part of their breast cancer treatment.
To assess the LVEF measures of different techniques, the following comparisons were carried out:
1. IS2 2D planar data and GE 2D reprojected planar data from SPECT acquisition. 2. IS2 2D planar data and GE 3D SPECT acquired data on 4DM SPECT MUGA software 3. GE 2D reprojected planar data from SPECT acquisition and GE 3D SPECT acquired data on
4DM SPECT MUGA software 4. GE 3D SPECT acquired data on 4DM SPECT MUGA software and on Cedars-Sinai QBS
LVEF 2D Planar and 2D Reprojection Comparison
To compare the LVEF between the 2D planar and 2D reprojected planar images, an anonymised and randomised observer study was performed with three observers. Each image was analysed using Corridor 4DM cardiac software. This method required the operator to draw a region of interest (ROI) around the left ventricle at end systolic (ES) and end diastolic (ED) with an automatic background ROI. The software then automatically interpolates the ROIs for the remaining frames. To compare the measurements, tests of statistical significance and correlation were performed alongside evaluation of the standard deviation, maximum difference and average difference between both cameras. A further investigation was carried out to assess the inter-operator variability.
SPECT RNVG Analysis
To assess the possibility of using the acquired 3D SPECT data from GE’s NM530C, two different software packages were used: 4DM SPECT MUGA and Cedars-Sinai Quantitative Bloodpool SPECT (QBS). To use the acquired SPECT data, it had to be reformatted from 24 frames into 16 frames to be used with the 4DM SPECT MUGA package. The reformatted image was also used for the Cedars-Sinai analysis for a fair comparison.
Figure 1 & 2: Discovery NM530C detector panel and pinhole collimator configuration.
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LVEF measurements were carried out on 28 patients, a randomly selected subset of the original 60 patients. The measurements obtained are early preliminary results as they have only been performed by one operator as a first attempt. To evaluate the 4DM SPECT MUGA package, each image was processed using the software which required the user to manually draw regions around the left ventricle on each frame using the short and horizontal long axis views.
For the Cedars-Sinai QBS, 15 patients were randomly selected from the 28 patient subset to provide a comparison between the two software packages. Processing was then performed using QBS which required the user to place markers at the septum, mitral valve and tricuspid valve and the programme automatically drew regions around both the left and right ventricles.
The LVEF measurements obtained using the 4DM SPECT MUGA package were then compared to the IS2’s reported planar value and the average LVEF for the reprojected planar obtained from the observer study results. A further comparison was then carried out to assess the relationship between the two SPECT software packages.
Statistical Analysis
To compare the function measurements achieved using the different imaging and analysis techniques, several statistical tests were performed. Firstly, the data was assessed for normality using the Kolmogorov-Smirnov test. It was found that it was not valid to assume that the data distribution was from a normal distribution, therefore, non-parametric statistics tests have been used.
To test for statistical significance, the Wilcoxon signed rank (WSR) test was applied which can be used with matched or repeated measures. The null hypothesis for this test is that the difference between datasets is not statistically significant, giving a p-value greater than 0.05. However, if the p-value returned is less than 0.05, this indicates statistical significance. To assess correlation, the Spearman’s correlation coefficient test was performed; a non-parametric test to quantify the degree of association between two variables. A coefficient of zero indicates there is no correlation between the two sets of data. However, a correlation coefficient of one or negative one means the two datasets have perfect correlation and the polarity determines if it is a positive or negative relationship [4] (Bland JM , 2000).
Bespoke Dynamic Cardiac Phantom Prototype
To provide a more accurate quantitative comparison between the two cameras, a bespoke dynamic cardiac phantom prototype was designed and manufactured. Before the initial design, the phantom requirements had to be established. Following discussions with the department’s physicists, the main requirements were to have a left and right ventricle that could be filled and emptied with known ejection fraction volumes. It was also desirable to have a fillable myocardial wall, allowing the phantom to be used for RNVG and myocardial perfusion imaging. Following a thorough literature and market review, it was found that there were no commercially available phantoms that met these requirements so the phantom had to be produced in-house. The first stage in the design process was to determine how to provide the power and mechanical motion to allow for a dynamic phantom with two filling ventricles and a filling myocardial wall. It was found that a single slider crank shaft mechanism would be easiest to produce whilst providing linear motion to operate multiple syringes.
Figure 3 shows a similar set up to the crank shaft method applied in this phantom. A rotary motor would be used to spin a Perspex disk which attached to a crank and connector rod. The connector rod is then attached to a piston which provides the linear motion by travelling between two guide rods. The piston would then be attached to another component which would connect to three syringes, providing motion to fill and empty the ventricle and myocardial wall containers. The Perspex disk would have three different connector holes to allow for a smaller rotation circle providing a shorter distance for the piston to travel and therefore, lower volumes when using syringes.
Figure 3: Dynamic cardiac phantom mechanical components providing linear motion to three syringes.
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Results
LVEF Comparison Operator Comparison
Firstly, an evaluation of inter-operator variation of LVEF measurements was performed, quoting the standard deviation, WSR p-value, correlation coefficient and maximum and mean difference.
Comparison Standard Deviation
WSR
P-value
Correlation Coefficient
Maximum Difference
Average Difference
IS2 2D Planar LVEF Measurements
Operator 1 and 2 4.2% 0.69 0.96 11% -1%
Operator 1 and 3 3.5% 0.74 0.97 10% -1%
Operator 2 and 3 3.7% 0.93 0.97 13% 0%
GE’s NM 530C Reprojected 2D Planar LVEF Measurements
Operator 1 and 2 5.4% 0.76 0.92 16% 1%
Operator 1 and 3 4.4% 0.9 0.95 15% 0%
Operator 2 and 3 4% 0.66 0.96 12% 1%
The findings in table 1 indicate that the difference is not statistically significant between operators with strong correlation between the two datasets. It was also found that the standard deviations, except one, fell within 5% of each other, highlighting an acceptable difference clinically. However, the maximum differences were higher than expected which requires further investigation to assess studies with differences greater than 5% as this would impact on the patient’s treatment.
Camera Comparison
A comparison between the two cameras was then carried out for each operator’s results in the observer study; table 2 shows the standard deviation, WSR p-value, correlation coefficient, maximum difference and average difference. These results indicate that there is no statistical significance as all of the p-values are greater than 0.05 and the correlation coefficients show there is a strong relationship between the two measures. The standard deviations suggest that the difference between the two measures could be clinical significant as they exceed 5%. To further compare these measures, Bland Altman plots were produced which assess the difference and the average between two measures.
Comparison Standard Deviation
WSR P-value
Correlation Coefficient
Maximum Difference
Average Difference
Reprojected vs Planar Operator 1 7.6% 0.28 0.85 26% 3%
Reprojected vs Planar Operator 2 5.7% 0.73 0.92 12% 1%
Reprojected vs Planar Operator 3 5.8% 0.38 0.91 14% 2%
Table 1: Operator comparison of LVEF measurements for planar and reprojected planar images.
Figure 4: Bland Altman plots showing planar and reprojected planar LVEF measurement comparison.
Table 2: Camera comparison of LVEF measurements for planar and reprojected planar images.
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These Bland Altman plots suggest the reprojection LVEF is consistently larger than the planar LVEF, however, each operator has similar confidence of limits, determined by the standard deviation.
SPECT Comparison
To evaluate the LVEF measures obtained using the SPECT images, the results were compared to the reported IS2 planar value and the average reprojected LVEF found in the observer study.
The results in table 3 indicate that there is no statistical significant difference between the two 2D planar techniques and the 3D SPECT LVEF measurements with good correlation. The maximum differences and standard deviations were larger than expected and this requires further assessment. However, it was found that the two SPECT methods were close to being statistically significant and a maximum percentage difference of 35% would be clinically significant. Bland Altman plots show that the SPECT LVEF measurements are slight overestimated when compared to both the planar and reprojected LVEF results. There is however, a large difference between the LVEF measurements found using both SPECT packages, with Cedars-Sinai typically being much larger than 4DM SPECT MUGA. However, these plots highlight that there are several outliers with larger differences which could potentially skew these results. Further evaluation of both software programmes is required following staff training and using larger patient datasets.
Bespoke Dynamic Cardiac Phantom
The final phantom design was decided as the slider crank shaft mechanism and it was found that the phantom was fully functioning and could be used to acquire images for a comparison between the two cameras. Figure 6 shows initial test images from the NM530C, reprojection planars at multiple views.
Comparison Standard Deviation
WSR P-value
Correlation
Coefficient
Maximum Difference
Average Difference
Reported Planar vs SPECT (4DM) 8.2% 0.55 0.79 19% 2%
Reprojection vs SPECT (4DM) 9.1% 0.85 0.78 18% 1%
SPECT (4DM) vs SPECT (QBS) 10.3% 0.053 0.81 35% 11%
Figure 5: Bland Altmann plots showing reported planar, reproject and SPECT LVEF comparison.
Figure 6: Test images of the dynamic cardiac phantom on GE’s NM 530C.
Table 3: Planar, reprojected and SPECT comparison of LVEF measurements.
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Discussion and Conclusion The results of this project found that the difference between the planar and reprojected planar LVEFs are not statistically significant and standard deviations did not exceed 5%, therefore these images could be used to obtain LVEF measurements. The results of a previous audit found that intra-operator variation is about 3%, therefore highlighting a difference of less than 5% would be acceptable. Further assessment will be carried to assess the clinical significance for differences greater than 5% as this would impact on a patient’s treatment. Evaluation of wall motion and increased background counts will also be carried out to further assess the acceptability of using the reprojected images clinically. The SPECT RNVG LVEF results are preliminary results from one operator, done as a first attempt. A training session has been requested with 4DM to better understand SPECT processing. However, these results indicate a good correlation between the measurements, showing potential for use of SPECT RNVG in the future. The final dynamic phantom prototype has been created and is fully functioning with initial test images acquired using the NM530C.
References [1] GE Healthcare, CZT Technology: Fundamentals and Applications – White Paper, [Available online: http://www3.gehealthcare.pl/~/media/documents/us-global/products/nuclear-medicine/whitepaper [2] Gimelli, A, Alcyone Technology, Healthcare in Europe [Available online: https://healthcare-in-europe.com/en/news/alcyone-technology.html], 3rd of November 2010, Accessed 12th of October 2019 [3] Erik Mattsson, The Alcyone CZT SPECT camera. Evaluation of performance using phantom measurement and Monte Carlo simulations, Department of Medical Radiation Physics, Lund University, 2013 [4] Bland JM. An Introduction to Medical Statistics, 3rd edition. Oxford Oxford Univ Press. 2000;137–55.
B)
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Impact on SPECT Reconstruction of Iterative Metal Artefact Reduction Miss L. Urquhart, Dr C. Brown
Nuclear Medicine Department, Gartnavel General Hospital, Glasgow
Introduction Hybrid SPECT-CT imaging is commonly used to simultaneously obtain functional and anatomical images respectively. In the reconstruction of SPECT data, Hounsfield Units (HUs) from the CT image can be converted to an attenuation coefficient map. This map is used to correct for photon attenuation, commonly known as CT-based Attenuation Correction (CTAC). The presence of high-density objects such as metal prostheses can cause photon starvation or under-sampling which can generate artefactual HUs (1). Therefore, these artefacts in the CT data could propagate to the SPECT data and, furthermore, degrade the accuracy of SPECT quantification. Siemens Healthcare have introduced an Iterative Metal Artefact Reduction (iMAR) algorithm which has been widely implemented for CT applications (2, 3). However, it is unknown what effect using this iMAR algorithm to generate the CTAC map will have on the quantification and visualisation of reconstructed SPECT data. To evaluate the effect of iMAR on SPECT reconstruction, this project comprised of two parts: a phantom study and a clinical study. The phantom study aimed to investigate the quantitative accuracy of SPECT data reconstructed with an iMAR CTAC map by analysing Standardised Uptake Values (SUVs) and CT HUs. Additionally, the effect of iMAR CTAC on three different orthopaedic metal implants was evaluated both quantitatively and qualitatively. The clinical study evaluated the use of iMAR in bone SPECT-CT studies where a metal implant was present. Assessment of the HUs and SUVs was carried out, along with a qualitative comparison of the SPECT and CT data reconstructed with and without iMAR.
Method Phantom Study: Phantom Design The phantom consisted of a 14 cm diameter cylinder in which a prosthesis surrounded by bone equivalent material could be inserted. Additionally, two 1ml sources were placed to simulate the increased uptake of a lesion (see Figure 1). Fifteen clinical SPECT-CT studies were analysed to determine average uptake ratios between soft tissue, normal bone (cortical and trabecular) and a typical lesion (displayed in Table 1). These values were used to guide the activity concentrations used to fill the phantom.
Table 1: The average count ratio obtained from 15
clinical SPECT-CT studies. Therefore, the cylindirical phantom was filled with Tc99m using a concentration ratio of 15:1 (insert: bgd) and 100:1 (source: bgd). Bone equivalent solution was prepared using a concentration of 1.4g/ml of dipotassium phosphate (K2HPO4) dissolved in water. This concentration has previously been demonstrated to have similar attenuation properties to that of bone (4). Tc99m was then added to this solution to simulate normal bone uptake. A total of four inserts were prepared for use in the phantom using 60ml syringes. The
Reference insert contained 50ml of Tc99m bone equivalent solution only. Three other syringes were
Normal Bone : Soft Tissue (BGD) 15 : 1
Lesion : Soft Tissue (BGD) 100 : 1
Figure 5: Phantom design.
Figure 6: The four phantom inserts used in this study.
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filled with Tc99m bone equivalent solution, but additionally contained a metal implant (Cobalt Chromium Alloy, Stainless Steel and Titanium Alloy). These implants had HUs of ~8000, ~9000 and ~4000 respectively. The four inserts are shown in Figure 2. Furthermore, a 1ml source of Tc99m simulating a lesion was inserted into each syringe, with a further source secured within the main cylindrical phantom (see Figure 1). The sources within each of the syringes will be referred to as ‘Source 1’ and the source within the main cylinder of the phantom will be referred to as ‘Source 2’. Quantitative Assessment: Phantom Data The SUVs of the 1ml sources were measured. Source 1 was used to evaluate intra-phantom consistency when iMAR was used for the CTAC map compared to standard reconstruction. Source 2 was used to determine the impact of the different metals on the performance of iMAR. A standard Volume of Interest (VOI) was used to compare SUVs and HUs for the two reconstructions. This was repeated three times to produce an average measurement. The ratio of the SUV in the SPECT reconstructions with and without iMAR enabled CTAC was determined for each phantom acquisition. The change in HU of this VOI was also noted. Additionally, the percentage difference in SUV between Source 2 in each acquisition with a metal prosthesis present and the reference, was determined for both iMAR and standard reconstructions. A Wilcoxon Signed-Rank Test was performed to determine statistical significance of the SUV
measured for each of the acquisitions with metal present compared to the reference acquisition. Furthermore, subtraction images for each pair of SPECT reconstructions (iMAR and standard) were produced. These were analysed using a fixed size VOI over the entire phantom to determine any quantitative difference in the SPECT reconstructions for each phantom. Qualitative Assessment: Phantom Data The respective pairs of CT reconstructions were visually evaluated by five experienced observers for all four phantom acquisitions. The observers answered a set of five qualitative questions on visual aspects of the reconstructions. Clinical Study: For the clinical study, six Tc99m bone SPECT-CT studies over a four month period contained metal in the field of view and were suitable for retrospective reconstruction with iMAR. Quantitative Assessment: Clinical Data For the six studies, CT data was reconstructed with and without iMAR. Both sets of CT data were analysed using line profiles. Placement of the line profiles was determined by finding the transverse image in which, visually, the prosthesis produced the greatest artefact. The line profiles were analysed to determine the absolute maximum difference in HU value observed between the standard and iMAR CTACs for the six clinical studies. In addition, these two CTs were used to correct for attenuation, producing two SPECT reconstructions for each clinical study. To assess the accuracy of SPECT reconstructions, SUVs were used to measure any discrepancy in activity concentration between the reconstructions with and without iMAR for the CTAC. This measurement was carried out by placing a fixed size Region of Interest (ROI) over an area visually affected by the metal implant on CT and a second ROI over an unaffected area, away from the metal implant. These ROIs were then copied to the SPECT data. The reconstructions were evaluated by determining the ratio of the SUV in an affected region in the reconstruction with iMAR CTAC compared to the same region in the standard CTAC reconstruction and the same for an unaffected region. The change in HU of these regions introduced by the use of iMAR was also noted. Results were tested for statistical significance using the Wilcoxon Signed-Rank Test. Qualitative Assessment: Clinical Data A visual assessment of the two SPECT and CT reconstructions for each clinical study was performed by one experienced observer.
Results Phantom Study: The ratios of SUV between the two sources in the cylindrical phantom, reconstructed with and without iMAR for generating the CTAC map, are shown in Table 2. This table also includes the difference in HU between the CTAC map with and without iMAR.
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Source 1 Source 2
Phantom Ratio of SUV
Difference in HU with iMAR
Ratio of SUV
Difference in HU with iMAR
Cobalt Chromium Alloy 1.00 +402 0.98 -361
Stainless Steel 0.98 -161 0.99 -72
Titanium Alloy 1.03 +567 0.98 -202
Reference Phantom 1.00 0 1.00 -2
Table 2: Intra-phantom analysis: SUV ratios for SPECT data reconstructed with and without iMAR for generating the CTAC map, and corresponding change in HU observed for each source.
The reference phantom demonstrated that iMAR has no affect on the HUs or SUV when no metal is present. It was also noted that the maximum difference in SUV between a standard SPECT reconstruction to an iMAR CTAC reconstruction was 3%. The difference in SUV between Source 2 in the reference phantom and those containing metal prosthesis is shown in Table 3.
% Difference in SUV of Source 2 from Reference
Reduction in SUV with
iMAR Enabled
Wilcoxon Test Statistic (compared to Reference
Phantom SUV) Phantom
Standard reconstruction
iMAR reconstruction
Cobalt Chromium Alloy 15.8 14.1 1.8% W(6)=0
Stainless Steel 7.9 6.8 1.1% W(6)=0
Titanium Alloy 16.8 14.6 2.2% W(6)=0
Table 3: Inter-phantom analysis; difference observed in the SUV of Source 2 when metal implants were present compared to reference for iMAR and standard reconstructions, along with Wilcoxon Test Statistic (5).
Using the iMAR CTAC map improved the SUV of the SPECT reconstruction for all three prosthesis. However, the improvement in SUV is relatively small compared to the offset from the reference phantom. The subtraction images demonstrated a variation in total SUV of <2% between the two SPECT reconstructions for all three phantom acquisitions containing a metal prosthesis. This result provides confidence that the iMAR algorithm doesn’t introduce any artefacts affecting the quantification of the SPECT data.
Respective pairs of CT reconstructions for all phantoms are shown in Figure 3 and the results from the qualitative assessment of this data are shown in Table 4.
Figure 7: Visual presentation of standard and iMAR reconstructions for all phantoms.
iMAR has:
Visualisation of: Has iMAR introduced any new artefacts?
Metal Prosthesis
Soft Tissue Source 1 Source
2
Improved 27 % 93 % 33 % 60 % YES: 33 % NO: 67 %
No Change 73 % 7 % 27 % 40 %
Worsened 0 % 0 % 40 % 0 %
Figure 8: Visual presentation of standard and iMAR reconstructions for all phantoms.
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Table 4: Results from the visual assessment of the CT reconstructions (n=5 observers; n=3 phantoms).
Clinical Study: Examples of line profile placement for areas affected by photon starvation and under-sampling from a patient with bi-lateral hip replacements are shown without and with iMAR enabled in Figures 4a and 4b respectively. These profiles demonstrate the application of iMAR in changing the CT number in areas affected by metal artefact. The largest difference in HU observed from these line profiles between the standard and iMAR CTs over all clinical studies examined was 1732HUs.
Standard Reconstruction
iMAR Reconstruction
Figure 4a: Horizontal line profile (red line in image) from regions affected by photon starvation.
Figure 4b: Vertical line profile (yellow line in image) from region affected by under-sampling.
Table 5 displays the results from SUV analysis of the 6 clinical studies, along with the corresponding change observed in HU in these regions. The SUV ratio between the SPECT reconstructions (with and without iMAR CTAC) in an affected region demonstrates that iMAR is having an impact on the SPECT quantification. This correlates with the change in HU due to iMAR in that region. The SUV ratio and corresponding HUs in an unaffected region have not changed. The Wilcoxon Signed-Rank test has demonstrated that the only statistically significant difference is the change in HU due to iMAR in a region affected by metal artefact. The visual assessment of the six clinical studies demonstrated consistent overall improvement noted in all CT studies when iMAR was applied and no new artefacts were noted. However, there was no notable visual difference to the SPECT images.
Region affected by metal artefact Region unaffected by metal artefact
Patient Study Ratio of SUV Change in HU due Ratio of SUV Change in HU
iMAR has:
Visualisation of: Has iMAR introduced artefacts?
Metal Prosthesis
Soft Tissue
Source 1 Source
2
Improved 27 % 93 % 33 % 60 % YES: 33 % NO: 67 %
No Change 73 % 7 % 27 % 40 %
Worsened 0 % 0 % 40 % 0 %
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to iMAR due to iMAR
1 1.01 +49 1.00 -1
2 0.93 +218 1.00 +1
3 1.12 +365 1.00 0
4 1.16 +313 1.04 +1
5 1.06 +116 1.01 -1
6 1.09 +319 1.00 0
Wilcoxon Test Statistic
W(6)=3 W(6)=0 W(6)=4 W(6)=10
Table 5: Average SUV ratios and corresponding average change in HU observed for areas affected by metal artefact and not affected in both iMAR reconstructions and standard reconstructions. Wilcoxon Test Statistic (5).
Discussion The aim of this project was to study the effect on SPECT data corrected for attenuation using a CT map with and without iMAR. More specifically, the effect on SPECT data from three prosthesis corrected using iMAR CTAC was assessed. Quantification of the reference phantom demonstrated that the iMAR algorithm has no effect on the SPECT or CT data when no metal is present. It was seen that iMAR had a larger effect on the HU in Source 1 than Source 2, which would relate to the different density of the surrounding material. However, this difference in HU induced a maximum difference of 3% in SUV between the SPECT reconstructions (with and without iMAR), which is not of clinical significance (as errors of >15-20% in SUV can be expected in clinical practice (6)). This small degree of change in the SUV, induced by a statistically significant change in HU was expected. For example, conversion of a change of ~400 HU to an equivalent attenuation coefficient demonstrates an increase of only ~10% over a few pixels, hence, would not induce a significant change in SUV. Source 2 within the phantom background was used for inter-phantom analysis. The phantom containing the titanium implant displayed the largest difference in quantification of Source 2 compared to the reference phantom. However, the titanium prosthesis was largest out of the three implants, which may have had an impact on the result. A Wilcoxon Signed-Rank Test showed the presence of metal in the phantom did significantly affect the SUV of Source 2 (W(6)=0 for all phantoms containing metal, significant when W(6)≤0 (7)). However, the relative change in SUV was negligible and remains clinically insignificant (6). As expected for clinical studies, observers noted there was an overall visual improvement of soft tissue around the metal implant seen in the CT when iMAR was applied. This compared with 60% of observers who noted an improvement in visualisation of Source 2 in the phantom. However, the majority of observers agreed that the visualisation of Source 1, within the bone equivalent solution, had worsened in the CT with iMAR applied. It was also noted that the air gap in Source 1 has been misinterpreted as an artefact by iMAR and subsequently been filled with tissue equivalent HUs. The introduction of new artefacts by iMAR was also seen in 33% of observations, most commonly in the phantom containing the titanium implant which agrees with the findings of Bolstad et al (8). Line profiles in the clinical CT data demonstrated how iMAR alters the CT number depending on the type of artefact present. For example, in an area of photon starvation, the HUs are increased whereas in an area of under-sampling the HU are reduced by the iMAR algorithm. However, when comparing affected and unaffected regions, a Wilcoxon Signed-Rank test showed that the only statistical significance between the different types of reconstruction (with and without iMAR) was that of the HU in an area affected by metal artefact. No statistical significance was found in the corresponding SPECT data of an affected area, or in the SPECT or CT data in unaffected areas. This finding provides confidence that iMAR only acts upon areas affected by metal artefact in the CT alone. The qualitative assessment of the clinical data confirmed consistent overall improvement in all CT studies with the use of iMAR, but no notable difference visible in the corresponding SPECT images. No new artefacts were observed in the clinical SPECT data reconstructed with iMAR CTAC. Further work is required to evaluate the use of iMAR in studies using isotopes other than Tc99m, however this would not be expected to significantly impact the results. Moreover, investigation into the impact of size and number of metal implants present is required. Additionally, no assessment was made of user definable parameters for iMAR.
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Conclusion This study confirmed that while the impact of iMAR on CT was statistically significant, concurrent with the findings of published studies, the impact of the iMAR CTAC on SPECT data was not as well-defined or quantitatively significant (3, 9). Nevertheless, the phantom study demonstrated that the presence of metal in general does cause a statistical difference to SPECT quantification when an SUV was compared to that from a reference phantom with no metal present. It was also observed that the application of iMAR to these metal phantoms does reduce this difference in SUV, bringing it closer to the reference value. However, the percentage improvement in SUV with the use of iMAR was not clinically relevant.
Acknowledgements Thank you to all my colleagues in Nuclear Medicine at Gartnavel and NHS Highland who have contributed to this project and also to Mr Martin Davison for kindly providing the orthopaedic prostheses.
References (1) Katsura M, Sato J, Akahane M, et.al. Current and Novel Techniques for Metal Artifact
Reduction at CT: Practical Guide for Radiologists. Radiographics, 2018; 38(2): 450-461. (2) Kachelrie M. Siemens White Paper. Iterative Metal Artifact Reduction (iMAR): Technical
Principles and Clinical Results in Radiation Therapy, 2015. (3) Hakim A, Slotboom J, Lieger O, et.al. Clinical Evaluation of the iterative metal artefact
reduction algorithm for Post-operative CT Examination after Maxillofacical Surgery. Dentomaxillofacial Radiology, 2017; 46(4).
(4) Dreuille O. Bone Equivalent Liquid Solution to Assess Accuracy of Transmission Measurements in SPECT and PET. IEEE Transactions on Nuclear Science, 1997. p. 1186-1190.
(5) Wilcoxon Signed-Rank Test Calculator. Date accessed: 16.10.2019. URL: www.socscistatistics.com/tests/signedranks/default2.aspx
(6) Kinahan P.E. and Fletcher J.W. Positron emission tomography-computed tomography standardized uptake values in clinical practice and assessing response to therapy. Semin Ultrasound CT MR, 2010. 31(6): 496-505.
(7) The Wilcoxon Test. Graham Hole Research Skills, version 1.0. (8) Bolstad K, Flatabo S, Aadnevik D, et.al. Metal Artifact Reduction in CT, a Phantom Study:
Subjective and Objective Evaluation of Four Commercial Metal Artifact Reduction Algorithms when used on Three different Orthopaedic Metal Implants. Acta radiologica (Stockholm, Sweden: 1987), 2018; 59(9): 1110-1118.
(9) Etemadi Z, Ghafarian P, Bitarafan-Rajabi A, et.al. Is Correction for Metallic Artefacts Mandatory in Cardiac SPECT/CT Imaging in the Presence of Pacemaker and Implantable Cardioverter Defibrillator Leads? Iran J Nuc Med, 2018; 26(1): 35-46.
Innovation Project: Thomas McMullan
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Long-term Outcomes of Prostate Cancer Patients Treated with Low Dose Rate Brachytherapy at Edinburgh Cancer Centre
Thomas McMullan1, Duncan McLaren2, Alastair Law2, Will Keough1, Tiffany Ronaldson1, Thomas
Berger1, Joanne Mitchell1, and Bill Nailon1.
1Department of Oncology Physics, Edinburgh Cancer Centre, Western General Hospital, Edinburgh. 2Department of Clinical Oncology, Edinburgh Cancer Centre, Western General Hospital, Edinburgh.
Introduction Prostate cancer is the most common form of cancer in men, in the UK, with 46,700 new cases diagnosed and 11,700 deaths each year; worldwide, approximately 1.13 million men were diagnosed with prostate cancer in 2012 - it is estimated that in their lifetime, 1 in 8 men will be diagnosed with prostate cancer [1]. Low dose rate (LDR) Brachytherapy has been shown to offer superior long-term oncological control compared to other treatment options, such as surgery, in low-risk patients, and equivalent to the combination of external beam radiotherapy (EBRT) and Brachytherapy in intermediate-risk patients [2]. LDR Brachytherapy is a treatment option offered at Edinburgh Cancer Centre (ECC) to patients with low or intermediate-risk prostate cancer. It involves the permanent implant of Iodine-125 (I-125) radioactive seeds into the prostate volume and is usually delivered as a curative monotherapy. At ECC, the implant procedure is a single stage technique carried out by a multidisciplinary team. Transrectal ultrasound is used to image the prostate and organs at risk, which are then delineated and used to produce a real-time treatment plan. This process has been in place at ECC since 2001, and as a result a significant amount of data exists relating to the treatment plans and patient-reported outcomes. The aim of this project was to report the clinical outcomes of prostate cancer patients treated with LDR Brachytherapy at ECC, using post implant dosimetry, 5 & 10-year overall survival (OS), 5 & 10- year biochemical relapse free survival (bRFS), disease specific survival (DSS), and prostate specific antigen (PSA) metrics. In this work, biochemical failure was reported according to the RTOG-ASTRO consensus conference definition [3]. Furthermore, the PSA nadir was the absolute lowest level that the PSA dropped following treatment, and initial PSA (IPSA) was the baseline PSA measurement prior to treatment. An additional aim of the project was to see if any of the PSA metrics had any predictive power in terms of predicting biochemical failure.
Methods Risk groups & patient characteristics A total of 544 patients were treated with LDR Brachytherapy up to December 2012, excluding 20 high-risk patients and those who had EBRT boost, or salvage Brachytherapy. The patient characteristics are summarised in Table 1. Low and intermediate-risk disease stratification followed the European Association of Urology (EAU) guidelines [4], where low-risk disease was defined as PSA < 10 ng/ml, Gleason grade < 7, and clinical stage T1-2a, and intermediate-risk disease was defined as PSA 10 – 20 ng/ml, or Gleason grade 7, or clinical stage T2b. Biochemical failure was defined as PSA nadir + 2 ng/ml, and excluded patients who had a transient rise in PSA (PSA Bounce) following treatment.
Table 2: Patient Characteristics
Low-risk Cohort Intermediate-risk Cohort
No. of patients 254 (47%) 290 (53%)
Median age (range) 62 (44 – 77) 64 (45 – 76)
Median IPSA (range) 6.0 (0.9 – 9.9) 8.8 (1.7 – 20)
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Dosimetry & Follow-up All patients had Brachytherapy as monotherapy, where the whole prostate volume was treated with a prescribed dose of 145 Gy, which was delivered by the implanted I-125 seeds. Most patients had 3-6 monthly interval follow-up for PSA testing, and a CT scan at six weeks, which was used for post-implant dosimetry. The dose to 90% of the prostate volume (D90), and the volume of the prostate receiving 100, 150, and 200% of the prescription dose (V100, V150, V200) were recorded from the post-implant dosimetry. PSA Kinetics We wanted to test the hypothesis “can PSA kinetics be used to predict 5-year biochemical failure in intermediate-risk patients?” To this end, we developed a model by applying a linear fit to the change in PSA of each patient over time, the output (slope and intercepts for each patient) of which was then used in logistic regression to evaluate how well the model predicted 5-year biochemical failure. Various models were tested for different PSA follow-up time ranges, ranging from 0-20, 0-27, 0-34, 0-36, 0-42, 0-48, 0-54, and 0-60 months. The performance of the models was compared using the area under the ROC curve (AUC). Once a suitable model was identified, the data was randomly split into 2/3 training set and 1/3 testing set, where the testing set was used to test if the training set model had any predictive power, which was again evaluated using the area under the ROC curve. Analysis Student t-tests were used to compare means in normally distributed data, and Mann-Whitney tests were used to compare medians in non-normal distributed data. An effect size was calculated when quoting p-values using the Mann-Whitney test.
Results
The 5 & 10-year biochemical relapse-free survival, overall survival, and disease specific survival, outcomes are summarised in Table 2. Of the 254 low-risk and 290 intermediate-risk patients, 3 (DSS 99%) and 12 (DSS 96%) patients died of prostate cancer, respectively. 5 and 10-year bRFS were 94% and 91%, respectively, in low-risk patients, and 86% and 81%, respectively, in intermediate-risk patients. 5 and 10-year OS were 96% and 90%, respectively, in low-risk patients, and 97% and 86%, respectively, in intermediate-risk patients.
Table 3: Low and intermediate-risk 5 & 10 year biochemical relapse-free survival, overall survival, and disease specific survival.
Low-Risk Disease Intermediate-Risk Disease
No. of Patients 254 (45%) 290 (51%)
Median age (range) 62 (44 – 77) 64 (45 – 76)
5 Yr bRFS 94% 86%
10 Yr bRFS 91% 81%
5 Yr OS 96% 97%
10 Yr OS 90% 86%
DSS 99% 96%
The box plots in Figure 1 are the results of comparing the median differences in IPSA and nadir in patients who survived at 5 & 10 years and those who had biochemical failure at 5 & 10 years. The median IPSA was higher in the patients who had 5-year biochemical failure in both the low (p=0.001) and intermediate-risk (p=0.002) cohorts. The median nadir was significantly higher in patients who had 5 and 10-year biochemical failure in both the low (5yr: p < 0.001, 10yr: p < 0.001) and intermediate-risk groups (5 yr: p < 0.001, 10yr: p < 0.001).
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Figure 9: Box plots comparing median IPSA and nadir with respect to 5 and 10-year biochemical failure in low and intermediate-risk patients, the median values are shown in red. (OS – overall survival, bR – biochemical relapse, bRF – biochemical relapse free)
Low-risk IPSA Low-risk nadir
Intermediate-risk IPSA Intermediate-risk nadir
Figure 10: Comparison of post-implant dosimetric parameters with respect to (wrt) 5 and 10-year biochemical failure, the median values are shown in red.
Intermediate-risk 5 yr biochemical outcome wrt
dosimetric parameters Intermediate-risk 10 yr biochemical outcome wrt
dosimetric parameters
There was also a statistically significant lower median nadir in intermediate-risk patients with 5 and 10-year overall survival (5 yr: p = 0.001, 10 yr: p = 0.013). Figure 2 shows that intermediate-risk patients who had biochemical failure at 5 and 10 years had lower V100, V150, V200, and D90, than those who didn’t fail. Of the intermediate-risk patients, those with IPSA > 10 ng/ml had higher rates of biochemical failure, bRFS 81% and 77% at 5 and 10 years, respectively, compared to those who had IPSA < 10 ng/ml, bRFS 91% and 84% at 5 and 10 years, respectively. On univariate analysis, younger men were more likely to bounce (p = 0.008, low-risk and p < 0.001, intermediate-risk), and the bigger the difference between IPSA and first PSA measurement following treatment resulted in less biochemical failure in intermediate-risk patients (p < 0.001). On multivariate analysis, IPSA was predictive of being relapse-free; lower IPSA resulted in less biochemical failure (p = 0.005, low-risk and p = 0.012, intermediate-risk). On univariate and multivariate analysis, no dosimetric factors were found to predict overall survival or biochemical relapse-free survival.
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Figure 3 shows the plot of different PSA kinetic models AUC with time, the performance of the models improves with time. The model at the 36-month time point had an AUC 0.76 and had the potential to predict 5-year biochemical failure in up to 55% of patients. Figure 4 shows the ROC curve for the 36-month 1/3 testing data set, the model for which was developed with the 2/3 training data set. The 36-month AUC of 0.76 in Figure 3 was reproduced in the testing data set, AUC 0.77, thus demonstrating the robustness of the model. Figure 3: Plot of PSA Kinetic models AUC with time. The cumulative total percentage of patient who has failed at 36 months is shown in red.
Figure 4: ROC plot for the 36-month model.
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Discussion The 5 & 10 year biochemical relapse-free survival are similar to those reported elsewhere in low-risk patients [5, 6], and intermediate-risk patients [7]. In the post-implant dosimetry data, lower V100, V150, V200, and D90 were shown to result in more 5 and 10-year biochemical failure in intermediate-risk patients. The median values of these dosimetric parameters in patients who didn’t have biochemical failure (shown in red in Figure 2 - relapse free) could be used to guide Brachytherapy treatment planning. IPSA and nadir were predictive of biochemical failure. Not reaching a low nadir following treatment may be due to local recurrence or occult metastatic disease. Earlier intervention could be achieved with the ability to predict 5-year biochemical failure in intermediate-risk patients. These patients could be suitable candidates for PET prostate-specific-membrane-antigen (PMSA) imaging, which has the ability to detect small volume disease at very low serum PSA levels. Patients with three or fewer metastases in the bone or lymph nodes could receive stereotactic body radiation therapy (SBRT), while those patients with local failure alone could be suitable for salvage prostatectomy, or focal salvage Brachytherapy. The next stage would be to validate the PSA kinetics model on an independent data set.
Conclusion LDR Brachytherapy offers excellent outcomes in terms of overall survival and biochemical relapse-free survival in low and intermediate-risk prostate cancer patients. The IPSA and nadir are significant predictors for biochemical relapse-free survival, with lower levels being more protective against biochemical failure. Lower dosimetric parameters V100, V150, V200, and D90 were shown to result in more biochemical failure in intermediate-risk patients. A model was developed to predict 5-year biochemical failure in intermediate-risk patients, which could lead to earlier local curative salvage treatment; further validation of the model is required.
References [1] Prostate cancer statistics. Resources for health professionals; Available online: www.cancerresearchuk.org. [2] Grimm P, Billiet I, Bostwick D et al. Comparative analysis of prostate specific antigen free survival outcomes for patients with low, intermediate and high risk prostate cancer treatment by radical therapy. Results from the Prostate Cancer Results Study Group. BJU Int 2012; 109(Suppl. 1): 22–9. [3] Roach M. et al. Defining biochemical failure following radiotherapy with or without hormonal therapy in men with clinically localized prostate cancer: recommendations of the RTOG-ASTRO Phoenix Consensus Conference. Int J Radiat Oncol Biol Phys. 2006 Jul 15; 65(4):965-74. [4] https://uroweb.org/guideline/prostate-cancer [5] Dickinson PD. et al. Five-year outcomes after iodine-125 seed brachytherapy for low-risk prostate cancer at three cancer centres in the UK. BJU Int. 2014 May; 113(5):748-53. doi: 10.1111/bju.12358. Epub 2013 Dec 2. [6] Crook J. et al. 10-year experience with I-125 prostate brachytherapy at the Princess Margaret Hospital: results for 1,100 patients. Int J Radiat Oncol Biol Phys. 2011 Aug 1;80 (5):1323-9. doi: 10.1016/j.ijrobp.2010.04.038. Epub 2010 Aug 1. [7] Lamb DS. et al. A prospective audit of the 10-year outcomes from low dose-rate brachytherapy for early stage prostate cancer. N Z Med J. 2018 Nov 9;131(1485):13-18.
Innovation Project: Megara Srikaran
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The Use of Virtual Reality Technology To Improve Radiotherapy Information for Patients With Breast Cancer
Megara Srikaran1, Sankar Andiappa Pillai1, Kirsty Muir2, Damian Parr2 and Ewan Eadie3. 1. Medical Physics Department, Ninewells Hospital and Medical School, Dundee, United Kingdom.
2. Radiotherapy Department, Ninewells Hospital and Medical School, Dundee, United Kingdom. 3. Photobiology unit, Ninewells Hospital and Medical School, Dundee, United Kingdom.
Introduction Breast cancer (BC) is one of the most common malignancies, affecting 1 in every 8 women in the United Kingdom, with a high mortality rate [1]. Radiotherapy (RT) is a standard treatment for BC although undergoing RT treatment can be physically and psychologically stressful for patients [2]. Studies reported that preparatory information provided to cancer patients before and after treatment has the potential to reduce anxiety, fear and stress, leading to improved patient outcomes [1, 3]. However, information-seeking patients with BC should be given maximum information, and the information avoiders should be given minimum information [4].
At Ninewells, the breast RT information is currently given both orally and written (leaflets). The literature reports that 1 in 5 patients cannot read the information given to them [5]. Due to the busy nature of cancer centres, patient’s appointments have become shorter and the patients have less time to discuss their treatment and care with healthcare professionals, thus new educational strategies are needed [6]. Virtual reality (VR) tools have become increasingly popular in healthcare, currently at low cost and widely-available [7, 8, 9].This project used the VR technology as a communication medium to support patients’ emotional needs as they advance through the complex RT treatment pathway. The visualisation of the treatment room and the linear accelerator delivering the treatment within the VR environment was shown to help patients experience and prepare them for their upcoming radiotherapy, with the intention to reduce anxiety and improve patient satisfaction and compliance [2]. It also highlights the critical importance of patient compliance for correct positioning regarding treatment reproducibility, which is vital to accurate radiation dose delivery.
The main aim of the project was to develop a breast RT patient journey VR information resource with five embedded 360◦ videos. The content demonstrates the process and sensations the patient experience at each step of the breast RT pathway at Ninewells Hospital: getting to the Ninewells RT Department , Computed tomography (CT) scan, standard RT treatment room and clinical equipment (Linear accelerator and couch), RT planning process using patient’s planning CT scan and Nurse review appointment. The 360◦ videos were produced using a 360◦ camera and viewed in VR using a Smartphone and VR headsets; Google Cardboard viewers, Google Daydream View and Samsung Gear VR or PC (e.g. Oculus Go) VR headsets.
The second aim of the project was to test the viability of the VR technology in educating the patients using questionnaires. Initial patient and staff questionnaires were provided to obtain the necessary VR content. After the 360◦ demonstration videos were created, the multidisciplinary team (MDT) and patients that undergone breast RT were provided with the second set of questionnaires for beta testing, which involved testing the video content and quality. The results were used to optimise the final 360◦ videos. The patient confidence questionnaires were provided before and after the use of VR resource. In this paper, we describe the technical production process of the RT VR information resource and report patient and RT MDT evaluation results on the viability of VR in helping patient experience and preparing them for their upcoming radiotherapy.
Materials and Method
Approvals: The Tayside Medical Science centre (TASC) Research governance department was contacted regarding the requirement of an ethics application, but the project was classified as a service development. The project was approved by the NHS Tayside Clinical Governance Department and the 360◦ Yi camera was registered with the Clinical Photography Department to comply with the NHS Tayside Policy on Recordings for Clinical and service use. All the patient and staff questionnaires were approved by qualified Physicists, Therapy Radiographers and the Tayside Communications Department.
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The project concept along with a VR technology demonstration was presented to the Ninewells MDT and a breast cancer networking group at Maggie’s centre, Dundee. The initial questionnaires were then provided to obtain necessary video content and feedback.
Production of the 360◦ demonstration videos and testing by RT staff and patients
The 360◦ videos were filmed using the Yi 360° VR camera, Figure 1, at a resolution of 5k. Positioned on a tripod, the camera was remotely controlled using a Samsung galaxy s8 mobile phone. The scripted demonstration 360◦ videos were filmed for ‘Getting to Ninewells RT department’, ‘The planning CT Scan’ and ‘RT treatment delivery’. The camera has two lenses; 360◦ videos from each lens were combined to produce a single equirectangular video format through a process called stitching using Yi 360° software. Filming was performed with the camera in a static position to avoid motion sickness to the viewer in VR [9, 10] results in multiple videos which were combined and edited using VIRB Edit and Adobe Premiere Pro CC software. The editing steps involved cropping the video timeline to remove any unwanted footage from the start to end and final 360◦ videos were exported to YouTube. The beta testing questionnaire was used to obtain feedback on the content, visual and sound quality of the 360◦ demonstration videos. The patient recruitment involved advertising using a poster, presenting at the Maggie’s centre, and asking patients currently undergoing breast RT whether they wished to participate in testing 360◦ demonstration videos. The demonstrations videos were shown to the patients aged from 33-70 years and the initial patient questionnaires were performed in a semi-interview format to obtain feedback on the project concept, video content and to identify the suitable implementation point in the breast RT pathway. For safety reasons, it was ensured that patients were sat in a swivel chair while
they were immersed in VR.
Filming the final RT patient journey 360◦ videos The patient and staff questionnaire feedback were analysed and the results were used to optimise the camera settings and video content before the final filming. The project and 360◦ filming process and structure of radiotherapy virtual experience (Refer Table 1) were discussed in detail with all the RT staff volunteers and consent was obtained. The scripted videos were filmed for ‘Getting to the Ninewells RT Department’, ‘The Planning CT scan’ and ‘Treatment delivery’ using Yi 360◦ camera with the same set-up as the demonstration videos. The resolution was set to 4k to allow in-camera stitching and reduce buffering issues. The videos were edited using Premiere CC software with the VR video sequence setting. During the filming, even experienced staff needed to practice in front of the camera, this resulted in a number of shots for each scene. The best shots were chosen and cropped for each scene to include in the final 360◦ videos. The volume levels were also adjusted to ensure consistency across the clips and the volume of the Linear accelerator was reduced such that it was realistic to what the patient would hear during treatment delivery. It was ensured that the same relative dimensions of the video were maintained during the import process of the editing software and out of the editing software when exporting to YouTube (e.g. Stereoscopic video file format) or a computer that supports the 360◦ video viewers. Various issues related to 360◦ filming are described in the literature and key aspects to consider if a VR experience is to feel immersive and fulfil the 360◦
space by various authors [9, 10, 11]. We checked the video within a VR headset at the end of each scene to avoid such pitfalls and ensure the quality of the video and audio were adequate for use and no sensitive information was captured in the 360◦ footage as it was filmed in a clinical environment.
Figure 1: Yi 360◦ Camera
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Table 1 Structure of the Radiotherapy Virtual experience
1. Getting to the Ninewells Radiotherapy Department: The Healthcare Assistant walks to the Radiotherapy reception from the Princess Alexandria entrance including visuals of the waiting area, water fountain and a vending machine.
2. Planning CT scan for Breast RT: The patient meets the Radiographers and then the patient walks into the CT room and is asked to get on the couch with the breast board. The Radiographer explains the CT process and that the CT scan is used for RT planning. The visuals of the CT scan process including the reference marks are demonstrated. End of the scan, the patient is provided with a gown, skincare advice leaflet during the Radiotherapy treatment. The Radiographer also answers frequently asked questions from the patient.
3. Breast RT Treatment Delivery: The Patient meets the Therapy Radiographer, they both walk into the treatment room 3. Therapy Radiographer explains the treatment process to and the Breast Radiotherapy patient set up is demonstrated. Visuals of the Linear Accelerator (Radiotherapy treatment machine) and its movement during treatment delivery and image acquisition using the on board imager are also demonstrated. Finally, the Radiographer answers frequently asked questions and gives the patient a holistic needs assessment appointment with the nurses to support with any symptoms and concerns which arise during the treatment.
Note: A Therapy Radiographer participated as a patient actor in all the 360˚ videos and a real patient were not involved in the filming process.
Development of Breast RT Journey VR Information Resource and Evaluation by New RT Patients with BC The RT journey VR information resource (Refer Figure 2) for patients with BC was developed in Microsoft PowerPoint and exported in a pdf format to ease distribution, to enable users to display the breast RT patient journey in 360˚ using a smartphone, tablet device and in VR using VR headsets. Quick Response (QR) codes were used to embed the 360˚ video, which can be scanned using any QR reader to load the 360˚ videos of the breast RT journey hosted on YouTube. A flyer with the project information was sent to patients who were referred for breast RT. These patients were then approached by the Radiographers after their oncology appointment to confirm their participation in the project. If they consented to participate in the project then the final ‘Getting to the Ninewells RT department’ and ‘The planning CT scan’ videos were shown to them in both VR and 360˚ format. The CT and treatment delivery confidence questionnaires were both designed to ascertain the participants’ level of anxiety related to RT before and after using the VR resource. The CT patient questionnaire was performed in a semi-interview format. The VR resource in Figure 2, was then given to the patient enabling them to access the ‘RT Treatment delivery’ video at home. How to access 360◦ videos using the QR code was demonstrated to the patients in 360◦ video format using an iPad and in VR using a Samsung S8 smartphone and Homido GRAB VR headset. An antibacterial wipe was used to clean the VR headset after each use for infection control purpose. The confidence questionnaires were performed throughout their RT pathway; pre and post CT and also Pre and post first fraction treatment. Results and analysis Qualitative methods Figure 2 RT journey VR information resource for patients with BC
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were used to analyse the questionnaire feedbacks and summary points are shown below for each of the questionnaires. 1. Patient initial Questionnaire Results Summary: 13/14 patients (age range: 33-70 years) reported that they were nervous coming to RT due to the unknown. Patient feedback highlighted that 14/14 patients wanted to receive treatment information in both 360◦ videos and VR. All the patients reported the project was a good idea and videos would have been useful to them, some of the comments are listed below:
2. Staff Questionnaire Results Summary: All 23 RT staff (Oncologists, Physicists, Healthcare Assistants, Therapy radiographers and Nurses) who completed the initial questionnaire highlighted that the project was a good idea and had the potential to benefit patients. Some of the staff feedback is listed below. The questionnaire results highlighted 17/22 RT staff were interested in testing the demonstration videos and providing feedback.
3. New Patient’s Confidence Questionnaire Results Summary: Seven patients (Age range: 40-81 years) were asked to score their anxiety levels before using the video resources and after watching the treatment delivery videos. The results in Figure 2 illustrate the anxiety levels are reduced in some patients, however, it cannot be concluded that this was due to the videos without control groups. Patient 2 and 7 were not anxious regarding the Radiotherapy process. 7/7 patients responded ‘Above Average’ and ‘Excellent’ to videos being informative and easy to understand and also ‘Agree’ to videos accurately represented their Radiotherapy experience. All the patients report that it also helped them understand the treatment and CT process. Some of the comments from the patients are listed below:
Figure 3 Patient Confidence Questionare - Anxiety Score
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Discussion The patient and staff questionnaire results highlighted the potential benefit of using 360◦ videos and VR as an information resource, with the majority of the patients reporting it as enjoyable and helped them. A number of studies [3, 12, 13] also confirm that the patients and relatives welcomed further information on RT planning, when delivered using Virtual Environment Radiotherapy training (VERT) as it helped them to improve their knowledge with a sense of empowerment, as well as reducing anxiety and fear about RT. It was interesting to observe the patients watching the demonstration 360◦ videos and they took the opportunity to look around the 360◦ space and watched the whole length of the video. Regarding the length of the videos contents, the Physicists recommended keeping the video short to prevent the viewer losing interest. However, the Therapy Radiographers pointed that the video should mimic the real planning CT or RT treatment experience as much as possible and also the necessary information should be provided without causing anxiety. Therapy Radiographer’s feedback also mentioned to include ‘Imager aspects’ during RT treatment delivery to demonstrate how close the Onboard Imaging system (OBI) gets to the patient. This was added in the final video with patient lying on the treatment couch. In addition, the Linac head (collimator) rotation was simulated to enable the viewer to experience being in the therapy room in the treatment position. One of the patient’s comment while watching the videos, “Can they hear me?” proved the immersive effect of the VR and that they felt being in the treatment room rather than the interview room. The quality of the VR resource was evaluated by the patients using a Likert scale (poor, below average, average, above average and excellent). The one negative comment was the poorer resolution in VR. High definition or resolution is required to produce a clear picture in the immersive videos. However, there are two main issues; information in each frame stretched around a central point into a full 360◦ environment leading to significant loss of resolution. The second problem is that the video is being viewed at a distance approximately 2 inches from the user’s eyes, within the 360◦ video viewer and hence any reduction in definition becomes magnified to the viewer [10]. The appropriate resolution and audio quality were investigated using the demonstration videos. The demonstration videos were filmed at 5k resolution, this resulted in a number of issues including buffering because of the limited bandwidth, high storage requirement due to the large file size, longer stitching time, also sound lagging in display and editing devices depending on the device capability and internet connection speed. One of the patient reported that she could not access the videos at home due to the slow internet connection, this was also observed at times with the hospital internet connection. Some of the above mentioned problems were resolved when filming at a lower resolution of 4k. It is also worth noting that YouTube down samples the 360◦ videos according to the display device’s capability. Furthermore, demonstration video feedback highlighted that there was slight variation in audio across the 360◦ videos; this was due to the distance between the Yi 360◦ camera and the person speaking. Since the Yi 360◦ camera does have slots to connect the microphone, a volunteer was required to speak louder when they were further away from the camera to balance the sound variation. The Premiere CC software was used to balance the audio variation in the editing process. Additional feedback was gathered from Macmillan Nurses, a patient networking group with 10 patients and Clinicians from Inverness. They reported the Clinicians also found the videos too long but none of the patients did feel the same way. They mentioned that “the videos would be good for NHS Highland”. Their patients commented “how reassuring it would be to have shown their families who might be worried". NHS Highland independent feedback echoes the feedback from the semi-interviews and questionnaires at NHS Tayside, hence removing the likely biasing of the opinions from the host institution. Implementation is one of the main challenges of the project. The patient and staff questionnaire results highlighted that before coming to the Radiotherapy department was the most popular point to implement the breast radiotherapy patient journey videos, especially at the oncology appointment. This will require a risk assessment and further discussion with the MDT.
Conclusion Advancements in immersive 360◦ technologies have allowed us to produce VR experience in healthcare at a low cost. This preliminary testing of the demonstration videos and feedback were extremely valuable as they found several areas that could be improved. The ‘Getting to the Ninewells Radiotherapy department’ , ‘Radiotherapy planning CT Scan’ and ‘Radiotherapy Treatment delivery’ 360° videos were successfully produced, available on Youtube and can be viewed on smart phones, tablets, laptops and VR headsets. The feedback from the patients and MDT at Ninewells Hospital has been positive and VR technology has a potential to benefit patients.
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Future work The next step of the project is to produce further videos covering the ‘Introduction’, ‘Breast Treatment Planning and checking process’ and ‘Review appointment’. Audit of the VR resource in terms of ease of use and benefit will be performed with patients and the Therapy Radiographers after implementation. There is an interest in Ninewells RT department to develop similar VR resources for the other RT treatment sites, e.g. prostate, and head and neck.
Acknowledgements I would like to thank all my supervisors for their generous time and support throughout this project, especially Damian and Kirsty for performing the confidences questionnaire with the patients and helping me to perform the initial patient questionnaire with the patients. My special thanks to Jonathan Ashmore for all the technical support and advice throughout the project. My huge thanks and appreciations to all the patients and staff participated in the project, checking the 360◦ videos and providing their invaluable feedback. I also would like to thank Greg Hampson for assistance with script writing, filming and editing the videos. My final thanks Professor David Sutton (Medical Physics Department at Ninewells Hospital) for funding this project. References [1] Breast Cancer Now. (2016). Breast cancer facts. Available: https://breastcancernow.org/about-breast-cancer/want-to-know-about-breast-cancer/breast-cancer-facts?deep_link=breast%20cancer%20facts.Last accessed 15/11/2019. [2] Annette Boejen. (2017). Virtual reality helps patient’s education in radiation therapy. Available: http://www.eonsmagazine.eu/springsummer-2017/virtual-reality-helps-patient-education-radiation-therapy. Last accessed 27 November 2018. [3] Amy Waller . (2014). Interventions for preparing patients for chemotherapy. Support care cancer. 22, 2297–2308. [4] Rees CE, Bath PA. Information-seeking behaviours of women with breast cancer. Oncol Nurs Forum 2001;28:899–907. [5] BBC News. (2000). One in five UK adults 'illiterate'. Available: http://news.bbc.co.uk/1/hi/uk/811832.stm. Last accessed 10/05/2019. [6] MOYRA E. MILLS. (1999). The importance of information giving for patients newly. Journal of Clinical Nursing. 0 (8), 631-642. [7] F. Cosentino, N. W. John and J. Vaarkamp, (2017). "RAD-AR: RADiotherapy - Augmented Reality," 2017 International Conference on Cyberworlds (CW), Chester, pp. 226-228. [8] Boejen A, Grau C. 2011. Virtual reality in radiation therapy training. Surg oncol;20(30): pg 185-8. [9] Jonathan Ashmore. (2018). Virtual reality preparation of children for MRI scan. Available: https://www.researchgate.net/profile/Jonathan_Ashmore. Last accessed 27 Nov 2019. [10] O'Sullivan B, Alam F, Matava Creating Low-Cost 360-Degree Virtual Reality Videos for Hospitals: A Technical Paper on the Dos and Don’ts. J Med Internet Res 2018;20(7):e239. URL: https://www.jmir.org/2018/7/e239 [11] Slater M. Place illusion and plausibility can lead to realistic behaviour in immersive virtual environments. Philos Trans R Soc Lond B Biol Sci. 2009;364(1535):3549–3557. doi:10.1098/rstb.2009.0138 [12] Jimenez YA. (2018). Patient education using virtual reality increases knowledge and positive experience for breast cancer patients undergoing radiation therapy. Available: https://www.ncbi.nlm.nih.gov/pubmed/29536200. Last accessed 27 November 2018 . [13] VR: Enhancing the prostate cancer patients experience of RT Vanita Gandhi*, Kuthpady Shrinivas, Sarah Needleman. Royal Free London Found.