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4D: Adaptive Radiotherapy & Tomotherapy
Bhudatt Paliwal, PhD
ProfessorDepartments of Human Oncology & Medical Physics
University of WisconsinMadison
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Additional Contributors to this Talk
W. TomeDept of Human Oncology
T. McNutt, M. Kaus, V. Pekar, Philips Medical Systems
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Radiation Oncology Workflow
Simulation Immobilization
Forward PlanningTreatment setup
Dose computation
Inverse PlanningDefine Objectives
Optimize
Plan Analysis
Delivery System QA Dose Accuracy
Verify and Monitor Delivery
Deliver Treatment
Pre-Verify Dose/Position
Export to Delivery System
Target and Structure Definition
Image Patient
Adaptive Analysis
Pretreatment CT Guidance
Modify Plan/Patient Position
Multi-modality Imaging
Planning4D ComponentsDelivery
Export for Population
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Where is the greatest uncertainty now?
Treatment Uncertainties
0
0.1
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-50 -40 -30 -20 -10 0 10 20 30 40 50Deviation from ideal
Pro
ba
bilit
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Target
Biology
Motion
Setup
Delivery
Dosimetry
Total
IMRT Improved Delivery Uncertainty
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4D Radiotherapy Adaptation Considerations
Radiobiology
Portal Images
On-line Imaging(Spirometry)
Fractionation
Setup Error
Organ Motion
Plan Modification
Target Re-Assessment
Tumor Response
PhysicianPatient
Dose Verification
4D Dose Eval
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4D Approaches - Frequency
• Multi-Fraction - Weeks– Monitor course of treatment and modify
plan at intervals of multiple treatment fractions
• Inter-Fraction - Day– “Plan of the Day” treatments– Prostate, Head and Neck
• Intra-Fraction - Seconds– Use 4D images to generate plans that
adapt to breathing cycle during treatment– Lung
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• Is it possible to daily re-plan?– 3D Conformal? IMRT?
• Is it practical to manage all the accumulated data offline and periodically re-plan?
• Are breathhold techniques acceptable or do we require dynamic motion compensation in our delivery?
• Is the incremental clinical benefit worth the cost?
• Can the process be made efficient enough for the busy clinic?
• Could we increase time per fraction and reduce the number of fractions to improve delivery?
– Biology?– Reimbursement?
4D Treatment Planning4D Treatment Planning
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4D Component Organization
4D Data Management• Time Series Volume Data• Record of Treatment Delivery• Time Series Portal Images
4D Image Processing• Deformable Registration• Model Based Segmentation• Organ Propagation• 4D Visualization
4D Evaluation• Organ Motion Analysis• Setup Error Assessment• 4D Dose Evaluation• Radiobiological Assessment
4D Treatment Planning• Geometric Uncertainty Planning • Adaptive Plan Modification• Automatic Re-planning (3D, IMRT)• Intra-fraction Motion Planning
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PROSTATE EXAMPLE (Model-Based Image Segmentation*)
*Model-based image segmentation is a work in progress
Drag and Drop organs to Initialize Segmentation
Use 3D edit tool to improveinitialization for rectumPerform model-based
auto segmentationFine adjust with 3D edit tools
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Use 3D edit tools to improve breast modelsContinue adaptation to image dataSegmentation completeAdapt organ models to the image dataDrag and Drop OrgansUse 3D edit tool to initialize spine
BREAST EXAMPLE( Model-Based Image Segmentation*)
*Model-based image segmentation is a work in progress
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Summary
• 4D RT concepts represent a challenging new step for radiation oncology
• Various image processing tools show promise in automating the image segmentation process to identify organ motion
• Data management and automated analysis are required to enable adequate monitoring of the course of treatment
• Molecular imaging may play a strong role in assessing tumor response to therapy
• Economical benefit may be realized in the trade-off be geometrical vs. radiobiological sparing of normal tissues with reduced the number of fractions, and daily re-planning