Gamma Knife Collimator Alignment Correction via Optical Feedback
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Solution Overview
Problem
The existing gamma knife apparatuses face challenges in accurately aligning the collimator with radiation sources due to decreased motor accuracy and improper operation, leading to misalignment and increased penumbra at the focus, resulting in dose deviations during radiation therapy.
Innovation Solution
A method and apparatus that correct the collimator position by obtaining projection images of rays passing through collimation holes at multiple positions, determining the target position with the highest alignment based on gray values and penumbra values, and recording position parameters to control the collimator's movement, ensuring precise alignment and focused radiation delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the collimator is moved to the design position using motor drive, then the collimator can be positioned at the theoretical alignment position, but motor accuracy degradation and improper operation cause misalignment and increased penumbra
Solution Approach 1:
The patent replaces the mechanical motor-driven positioning system with an optical measurement and feedback system. Projection images are acquired at multiple positions, and image analysis (gray values, penumbra values) determines the optimal position, substituting mechanical precision with optical measurement precision.
Solution Approach 2:
The patent implements feedback by acquiring projection images at multiple collimator positions, analyzing the images to determine alignment quality (using gray values and penumbra values), and using this feedback information to identify the target position with highest alignment degree, thereby compensating for motor accuracy degradation.
2Measurement precision
If projection images are acquired at multiple collimator positions, then the optimal alignment position can be determined, but the correction process requires additional time and operational steps
Solution Approach 1:
The patent performs preliminary action by acquiring projection images at multiple predetermined positions (including design position and positions with small displacements) before final treatment. This preliminary measurement and analysis establishes the target position in advance, so that during actual treatment, the collimator can be quickly positioned without repeated adjustments.
3Manufacturing precision
If the collimator is misaligned, then the penumbra at the focus increases, but maintaining precise alignment requires complex measurement and correction procedures
Solution Approach 1:
The patent introduces an intermediary measurement system using projection images as a mediator between the collimator position and the alignment assessment. The projection images serve as an intermediate representation that can be analyzed to determine alignment quality without requiring direct measurement of the collimator's physical position or complex interferometric methods.
Data Source
AI summary
Embodiments of the present disclosure provide a method and an apparatus of correcting a collimator, which may correct a position of a collimator of a gamma knife apparatus. The method includes: separately obtaining a projection image of rays sequentially passing through collimation holes and an isocenter plane in the collimator in cases where the collimator moves to M positions; determining a target position with a highest degree of alignment of the collimator from the M positions according to obtained projection images of rays; recording position parameters corresponding to the target position, so as to control the collimator to move to the target position in a case where the a gamma knife apparatus is used for treatment.