Radiotherapy Setup Error Tracking with CV-PEV Encapsulation Metrics
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Solution Overview
Problem
Current radiotherapy systems lack quantitative metrics to accurately assess and track anatomical changes in patients during treatment, leading to potential misalignment of Clinical Volumes (CV) and Planning Envelope Volumes (PEV), which can result in inadequate radiation delivery or exposure to sensitive organs.
Innovation Solution
A method is introduced to determine an encapsulation metric by defining Clinical Volumes and Planning Envelope Volumes, calculating the shortest distance of representative points, and using a signed distance transform to quantify the extent of CV encapsulation within PEV, allowing for real-time monitoring and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If margins are applied to Clinical Volumes to create Planning Envelope Volumes, then robustness to patient position variation is improved, but manufacturing precision of radiation delivery deteriorates due to uncertainty about actual CV position within PEV
Solution Approach 1:
The system acquires treatment images during radiotherapy sessions, automatically contours the Clinical Volume in the treatment image, calculates the encapsulation metric to determine the actual position of CV within PEV, and provides feedback about position accuracy. This feedback loop enables real-time monitoring and correction of patient positioning, resolving the contradiction by maintaining robustness through PEV margins while improving precision through active position verification and correction.
2Ease of operation
If automated linear movement of patient couch is used for position correction, then ease of operation is improved, but measurement precision of anatomical changes deteriorates due to lack of quantitative metrics
Solution Approach 1:
The system introduces an intermediary quantitative measurement layer between the automated couch movement and the clinical decision-making process. The encapsulation metric serves as this intermediary, providing precise quantitative data about CV position within PEV. This allows the automated linear movement system to operate with measured precision, as the encapsulation metric provides exact numerical values for position deviation, enabling more accurate corrections.
3Ease of operation
If visual comparison of treatment image to planning image is performed, then ease of operation is improved, but measurement precision of anatomical changes deteriorates due to subjective assessment
Solution Approach 1:
The system replaces the mechanical/subjective visual comparison process with an automated computational system. Instead of relying on human eyes and judgment to compare treatment images with planning images, the system automatically contours anatomical structures, calculates spatial relationships, and computes the encapsulation metric. This substitution maintains ease of operation through automation while dramatically improving measurement precision by eliminating subjective assessment in favor of objective mathematical calculations.
Data Source
AI summary
A method and system for determining changes between a planning image and a treatment image of a subject is described. The method comprising the steps of: defining one of more clinical volumes on the planning image of a subject and defining a planning envelope volume around the clinical volume for the planning image; acquiring a treatment image from the subject for a location corresponding to the location of the planning image; wherein the treatment image will have the same planning envelope volume as the planning image; determining the location of the one or more clinical volumes on the treatment image relative to the planning envelope volume; determining an encapsulation metric for one or more of the clinical volumes defining the extent of encapsulation of the clinical volume on the treatment image within the planning envelope volume on the treatment image.