Radiation Control Using CT-Derived DRR Matching for Breathing Motion
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Solution Overview
Problem
Existing radiation treatment systems face challenges in accurately controlling radiation beams due to periodic fluctuations in tumor position caused by subject breathing, leading to inaccuracies in radiation delivery.
Innovation Solution
A radiation control apparatus that generates DRR images based on CT images and fluoroscopic images, calculates positional deviation using normalized correlation coefficients, and permits radiation only when the deviation is within a prescribed value, ensuring accurate tumor targeting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the radiation beam is irradiated continuously without positional verification, then the treatment efficiency is improved, but the radiation delivery accuracy deteriorates due to respiratory motion
Solution Approach 1:
The system performs continuous fluoroscopic imaging and real-time positional deviation calculation during radiation treatment, maintaining continuous verification without interrupting the treatment workflow. The automated comparison between fluoroscopic images and DRR images enables continuous monitoring of tumor position while the radiation beam is delivered, ensuring both efficiency and accuracy.
Solution Approach 2:
The system establishes a feedback loop by continuously acquiring fluoroscopic images, calculating positional deviation from the treatment plan, and using this information to verify whether radiation delivery conditions are met. This real-time feedback mechanism ensures that radiation is delivered only when positional accuracy requirements are satisfied, resolving the contradiction between continuous treatment and accurate delivery.
2Device complexity
If the positional deviation calculation uses only the original DRR image without shifting, then the calculation process is simplified, but the positional deviation measurement accuracy deteriorates
Solution Approach 1:
The system generates multiple shifted DRR images by applying small displacement amounts in the craniocaudal direction, then compares the fluoroscopic image with each shifted version. This partial action approach (shifting by small increments) balances the increased computational effort with improved measurement accuracy, finding the optimal match without requiring excessive computational resources.
Solution Approach 2:
The system pre-generates multiple shifted DRR images with predetermined displacement amounts before performing the positional deviation calculation. This preliminary preparation of shifted images allows for efficient real-time comparison during treatment, as the shifted versions are already available for immediate comparison with the fluoroscopic image.
Data Source
AI summary
A plurality of shift images are generated by shifting a fluoroscopic image by a prescribed increment within a prescribed range in a craniocaudal direction. Then, a normalized correlation coefficient between a DRR image and each of the plurality of shift images is calculated. Next, a shift amount of the shift image corresponding to the largest normalized correlation coefficient among the plurality of normalized correlation coefficients is determined to be the positional deviation.