Composite Image Creation for Radiotherapy Dose Planning
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Solution Overview
Problem
Existing radiotherapy treatment planning systems face challenges in accurately computing dose distributions due to the limited field of view of fraction images, which lack sufficient material property information outside the imaging area.
Innovation Solution
A computer-based method is developed to create a composite image of a patient by combining a fraction image with surface scan data to generate an outer contour and approximate anatomical information outside the fraction image's field of view, thereby extending the image's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If CBCT scans are used for fraction images, then imaging device complexity and cost are reduced, but field of view coverage and material property information are insufficient
Solution Approach 1:
The patent combines CBCT fraction image data with surface scan contour data to create a composite image. The surface scan provides the missing field of view coverage while the CBCT provides accurate material property information within its limited field of view, merging the strengths of both imaging approaches.
Solution Approach 2:
The surface scan acts as an intermediary that bridges the gap in field of view coverage. It provides contour information for regions outside the CBCT field of view, enabling complete patient geometry representation without requiring a full-coverage CT scanner.
2Measurement precision
If CT images are used for planning images, then material property information and dose planning accuracy are improved, but cost and device complexity increase
Solution Approach 1:
The patent applies local quality by using high-accuracy CBCT material property information only where needed (within the CBCT field of view for the tumor and surrounding tissues) while using surface scan contour data for regions outside this area. This localized approach maintains dose planning accuracy for critical regions while avoiding the costs and complexity of full-body CT scanning.
3Productivity
If water density assumption is used for regions outside CBCT field of view, then dose computation can proceed, but dose computation accuracy deteriorates
Solution Approach 1:
The patent copies contour information from the surface scan and uses it to define the patient geometry outside the CBCT field of view. This copied geometric data, combined with appropriate density assignments, replaces the inadequate water-density assumption and enables more accurate dose computation without significantly increasing computational complexity.
Data Source
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AI summary
A computer based method of obtaining a 3D image of a part of a patient's body is disclosed, based on a fraction image having a limited field-of-view and extending the field of view with information from an image of the patient's outline, obtained from a surface scan of the patient. Anatomical data from the planning image are preferably used to fill in the outline image, by means of a contour-guided deformable registration between the planning image and contour.