lens identification to prevent radiation induced cataracts ......#cmimi18 the problem in computed...
TRANSCRIPT
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Lens Identification to Prevent Radiation Induced Cataracts Using Convolutional Neural Networks
Ross Filice, M.D.Associate Professor
Chief of Imaging InformaticsMedStar Georgetown University Hospital
MedStar Medical Group Radiology
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Disclosures
Nvidia Corporation; Academic GPU grant
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The Problem
“…repeated exposure to head and neck CT is significantly
associated with increased risk of cataract incidence.”
Yuan MK, Tsai DC, Chang SC, Yuan MC, et al. The Risk of Cataract Associated With Repeated Head and Neck CT Studies: A Nationwide Population-Based Study. AJR Sep 2013; 201(3):626-30.
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The Problem
In computed tomographic (CT) imaging of the brain, the lens of the eye is of special concern, as cataract formation is a well-documented result of radiation damage.
Particular attention is paid to…cataracts…hence, threshold doses appear to be lower than previously considered.
ICRP, 2012 ICRP Statement on Tissue Reactions / Early and Late Effects of Radiation in Normal Tissues and Organs – Threshold Doses for Tissue Reactions in a Radiation Protection Context. ICRP Publication 118. Ann. ICRP 41(1/2).
Reimann et al. Organ-Based Computed Tomographic (CT) Radiation Dose Reduction to the Lenses: Impact on Quality for CT of the Head. JCAT May/June 2012; 36(3):334-8.
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The Problem
In computed tomographic (CT) imaging of the brain, the lens of the eye is of special concern, as cataract formation is a well-documented result of radiation damage.
Particular attention is paid to…cataracts…hence, threshold doses appear to be lower than previously considered.
ICRP, 2012 ICRP Statement on Tissue Reactions / Early and Late Effects of Radiation in Normal Tissues and Organs – Threshold Doses for Tissue Reactions in a Radiation Protection Context. ICRP Publication 118. Ann. ICRP 41(1/2).
Reimann et al. Organ-Based Computed Tomographic (CT) Radiation Dose Reduction to the Lenses: Impact on Quality for CT of the Head. JCAT May/June 2012; 36(3):334-8.
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AAPM – Routine Adult Head CT
To reduce or avoid ocular lens exposure, the scan angle should be parallel to a line created by the supraorbitalridge and the inner table of the posterior margin of the foramen magnum. This may be accomplished by either tilting the patient’s chin toward the chest (“tucked” position) or tilting the gantry. While there may be some situations where this is not possible due to scanner or patient positioning limitations, it is considered good practice to perform one or both of these maneuvers whenever possible.
https://www.aapm.org/pubs/CTProtocols/documents/AdultRoutineHeadCT.pdf
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AAPM – Routine Adult Head CT
To reduce or avoid ocular lens exposure, the scan angle should be parallel to a line created by the supraorbital ridge and the inner table of the posterior margin of the foramen magnum. This may be
accomplished by either tilting the patient’s chin toward
the chest (“tucked” position) or tilting the gantry. While there may be some situations where this is not possible due to scanner or patient positioning limitations, it is considered good practice to perform one or both of these maneuvers whenever possible.
https://www.aapm.org/pubs/CTProtocols/documents/AdultRoutineHeadCT.pdf
#CMIMI18 Futacsi B, Kovacs B, Karlinger, K. Dose alertness: how to lower lens dose in standard brain CT scans? Our clinical experience. ECR 2014.
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Previous Work at MGUH
Manual paper-based technologist feedbackResulted in improvement….
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Previous Work at MGUH
Manual paper-based technologist feedbackResulted in improvement….
…when project stopped returned to baseline.
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Continuous Feedback Works
Lumish et al. Reporting Scan Time Reduces Cardiac MR Examination Duration. JACR Apr 2014; 11(4):425-8.
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Continuous Feedback Works
Lumish et al. Reporting Scan Time Reduces Cardiac MR Examination Duration. JACR Apr 2014; 11(4):425-8.
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Methods
- 100 routine head CTs- 4128 512x512 3mm axial soft tissue kernel images- Manual bounding boxes drawn on eyes and lenses- CNN based on GoogLeNet with modification to allow simultaneous detection of two objects (eyes; lenses)- 10 studies consisting of 404 images used for testing- 138 routine outpatient exams over 2 months used to establish baseline technologist compliance
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Modified GoogLeNet
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Example Bounding Boxes
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Example Bounding Boxes
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Saliency Features
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Image and Study Level ResultsModel
Lens None
Trut
h Lens 45 2
None 1 356
Model
Eye None
Trut
h Eye 66 2
None 1 335
Sensitivity: 95.7%Specificity: 99.7%Accuracy: 99.3%
Sensitivity: 97.0%Specificity: 99.7%Accuracy: 99.3%
* Both FP had relatively low confidence scores* 1 lens FP was an implant; 1 eye FP was a lens
Study level accuracy: 100%
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Baseline Technologist Performance
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Baseline Technologist Performance
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Future Directions
- Automatically screen exams on ingestion- Notifications and/or reports for technologist leads- Evaluate for improvement
- Limitations: Sensitivity perhaps could be improved- Some patients cannot comply with positioning; some feedback mechanism to override or exempt “noncompliance”
