CT pediatry: influence of new technologies on patient dose

Redefining the Rules of clinical CT Imaging with Spectral Imaging and Iterative Reconstruction techniques

Johan de Mey PhD. MD Head of Radiology Department

Koenraad Nieboer MD Head of Emergency RadiologyNico Buls PhD. MScMedical Imaging and Physical Sciences Gert Van Gompel PhD. MScMedical Imaging and Physical SciencesToon Van Cauteren MScMedical Imaging and Physical Sciences

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Multislice CT and clinical outcome

DoseWorkflow

accuracyefficiency

function

Characterizationperfusion

Spatial ResolutionTemporalCoverageWhat makes a good CT?

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Low Dose CT = quality ?1980 2007: Dose optimalisation

More imagesHigher resolution

2008 - : Dose optimalisation

Less dose???Functional???Iterative reconDual energy

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Noise suppression The straightforward way increase # photons, increase patient dose (mAs)

120 mAs60 mAs

10 mAs

CTDIv = 0,8 mGyCTDIv = 5 mGyCTDIv = 10 mGy

4Erratic information

Effective doses for CT procedures(review over 20 published articles)

Does the age of the patient at time ofexposure affect the patient risk?

Children are 2-10 x more sensitive!Hall Pediatric Radiology Apr 2002 pg 226

source

Iterative reconstruction

sImage acquisitionsinogramdetector

source

Goal:reconstruction

Adaptive Statistical Iterative Reconstruction (0%.....100%) and noise0.8 mGy16.8 mGy

10 mAs30 mAs60 mAs120 mAsGE CT750 HD, 100 kVp, p = 0.9, r = 1, t = 2.5 mm, FOV = 230 mm

8Asir strength depends on initial noise levelCan not make a 60mAs like image from a 10mAs image

ASIR (60%) and Spatial resolution

ASIRFBP

Female 45Acute dyspnea, suspicion pulmonary embolism

Scan ParametersRange 26 cmNi: 30120KVASiR: 40% CTDIv 7.44 (mGy)E 2.7 (mSv)

0.625 mm

1.25 mm1.25 mm

Body PackersBody packers: low dose CT / GSI

ECR EPPOS: C-2068 ECR 2011 K. H. Nieboer, N. Buls, J. de Mey, G. Van Gompel; Brussels/BE, The use of iterative reconstruction in ultra low dose computed tomography for bodypacker screening

VeoTM future in dose reduction= Model Based Iterative Reconstruction

SYSTEM NOISE STATISTICSREAL 3D SYSTEM OPTICS

FBPVEOASIR

Iterative impact on image noise

Tube currentNoise

FBPASIR 50%VEOCTDIvol = 12.5 mGyResolution at standard dose

Performance at 6 lp/cm and 8 lp/cm

Catphan 504 phantom

Ultra low dose Chest follow-up with VEO4mAs, 0.06mSv*FBPVeoASiRTypical CXR effective dose is about 0.06 mSv. Source: Health Physics Society.http://www.hps.org/publicinformation/ate/q2372.html

* Determined by internal organ dosimetry on a humanoid phantom

Chest CT with Veo Cystic Fibrosis 26y * Obtained by EUR-16262 EN, using a chest factor of 0.017*DLPConversions of CTDI or DLP to effective dose are only rough estimations for children

CDTIvol = 0.10 mGy Effective dose = 0.05 mSv*

Chest CT with Veo Cystic Fibrosis 15y

FBP-images 2011Ultra low dose

Veo-images 2011Ultra low dose

FBP- Images 2010Low dose DLP = 2.51 mGy.cm CTDIvol:0,09 mGyDLP = 54,3 mGy.cm CTDIvol: 1,65 mGy

Scan protocol: 4 mAs, 80 kVSlice thickness: 0.625mm

95 % dose reductionVEO reconstruction 2011FBP reconstruction 2010Chest CT with Veo Cystic Fibrosis 15y

Chest CT with Veo Cystic Fibrosis 15y Veo-images: Ray Sum CTPrevious Chest X-ray

PATIENT 1 (2010)3Y Old, empyemaFBP-imagesCTDi 2.1

PATIENT 2 (2011)3 y old, empyemaVeo-imagesCTDi 1.25

40% dose reduction

Pediatric maxilo-facial CT with Veo 95% dose reductionCT at plain film dose+/- 0.06 mSv

70% dose reductionNo quality loss

50% dose and low KVpNo quality loss + 50 % contrast reduction

40% dose reductionBetter image, less artifacts

Equal dose and low KVpUp to 60% contrast reduction

Dual energyspectral imaging:Need for at least two datasets on different energy level

Dual tubeMaking two scansDual layer detectorPhoton counting

Discovery CT750 HD

Fast switching tube

Dual energyspectral imaging:Need for at least two datasets on different energy level

Dual tubeFOV max 33 cmSpectral filter on 140Making two scansTime DifferenceDual layer detectorResearchPhoton countingFutureFOV 50 cmReal Time

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Discovery CT750 HD

Photon energy with Tungsten? What is dual energy?

Mean 61.1 KeV120 KV scanMean 49.9 KeV80 KV scanMean 66.1 KeV140 KV scan

Spectral material differentiation

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From 2 datasets to 101 datasets? Is this real?

Phantom dataQualitative comparison DECT literature (NIST)ECR: B-851 Monday 14.00G. Van Gompel, N.Buls, K. Nieboer, J. de MeyAccuracy estimation of spectral attenuation curves obtained by dual energy

Cadaver blood vesselsFilled with CM concentration, GSI scan

ROI2: water + CMROI3: soft plaqueROI4: calcified plaqueClinical use?

Relative dose reduction? (No need for non-CE scans) Contrast reduction? (Higher contrast in image)

WaterIodine

Pleural effusion: Exudate >< transudate?ECR EPOS: C-1996 Y. De Brucker, N. Buls, G. Van Gompel, F. Vandenbroucke, H. Nieboer, T. De Keukeleire, J. de Mey; Brussels/BE Characterization of pleural effusion using dual energy CT: feasibility study.

Phantom size on quantitative iodine measurement: dual energy CT >< standard CT.

23 cm120 keVGSI 70 keV 17 cm2919310631893145 17 cm + t32553158range345Obtained CT-values (HU)

VAR10.9%1.6%

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StandardPhantom size on quantitative iodine measurement: spectral CT >< standard CT. 120 kV

DECT at 70 keVStandardSpectral

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Male 77Acute dyspnea, suspicion pulmonary embolism

Iodine image

Water imageMonochromatic 40 140 KeVAxial recon image

Water imageIodine imageScatterplot

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S

GSI: spectral imagingSubsegmental pulmonary embolismClinical value

Pulmonary embolism was not depicted during 1st reading on standard images

MD Iodine shows clearly a hypo perfusion on the left.

2nd reading confirms pulmonary embolism resulting from a small thrombus in a small pulmonary vessel

GSI allows physicians to detect pulmonary embolism by showing subtle lung perfusion defect

Embolism

70 keV images with lung window Iodine Based Images70 keV Monochromatic Images70 keV Monochromatic Images

Images Courtesy of Dr. Jean Louis Sablayrolles; Centre Cardiologique du NordPulmonary EmbolismClinical value

Pulmonary embolism was not depicted during 1st reading on standard images

MD Iodine shows clearly a hypo perfusion in left lung resulting from a pulmonary embolism. Hypo perfusion could not be seen on standard CT image

2nd reading confirms pulmonary embolism resulting from a small thrombus in a small pulmonary vessel

GSI allows physicians to detect pulmonary embolism by showing subtle lung perfusion defect

Standard 120 kV acquisitionMonochromatic with MARsGSI: Artefact reduction

MD Water (Iodine)80 keVMD Iodine (Water)55 keV

Images Courtesy of Pr Dacher, CHU de RouenIliac Stent BleedingClinical value

Endoleak is better visualized on low energy (55 keV) images (green Arrows)

MD Iodine suggests Iodine leak

GSI allows physicians to better visualize bleeding vs. conventional CT

70 keV image 110 keV images

Metal Artifact Reduction: Spine

GSI acquisition allows to create a spectrum of monochromatic images where beam hardening is highly reduced

In this case the radiologist could recover information previously hidden by the beam hardening

Images Courtesy of Dr. Sablayrolles, CCN, France

Thank you for your attentionStatistical iterative reconstruction: important dose reductionDose reduction up to 50% and same qualityScanning at low KVp and contrast reductionIn some cases alternative for plain film

Spectral imaging and real iterative rec.: a new dimension in CTUltra low dose at diagnostic quality up to 95% reductionArtifact reduction and high quality imagesCharacterization and differentiationContrast amount and concentration reduction

Conclusion: New dimensions in CT