Multi-Leaf Collimator Calibration for Distortion-Corrected Leaf Positioning
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Solution Overview
Problem
Existing radiotherapy systems face challenges in accurately calibrating multi-leaf collimator leaves due to lens distortion and manual placement of imaging markers, leading to time-consuming and inaccurate positioning of leaves, which affects beam geometry during treatment.
Innovation Solution
A computer-implemented method to correct lens distortion and measure minor offsets by generating undistorted images of collimator leaves, using a predetermined coordinate space and calculating distortion coefficients to accurately determine leaf positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional separate calibration methods are used for MLC positioning and dosimetry, then calibration time is reduced, but positioning accuracy and dosimetry accuracy cannot be simultaneously optimized
Solution Approach 1:
The patent combines separate MLC positioning calibration and dosimetry calibration into a single integrated calibration process. The system simultaneously determines positioning accuracy and dosimetry accuracy by processing detector data from a single calibration procedure, eliminating the need for separate calibration steps and achieving both accuracy types concurrently.
2Measurement precision
If complex calibration procedures are implemented to improve accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The calibration system performs multiple functions simultaneously - it determines both MLC positioning accuracy and dosimetry accuracy using the same detector array and data processing methodology. This multi-functional approach achieves comprehensive calibration without requiring separate complex procedures for each accuracy type.
Solution Approach 2:
The system uses detector data to create a digital representation of the radiation field and compares it with expected values to determine accuracy parameters. This computational copying and comparison approach simplifies the physical calibration process while maintaining high measurement precision.
3Measurement precision
If detailed detector arrays are used to improve calibration accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The detector array is segmented into multiple independent detectors positioned at different locations. Each detector provides localized measurement data that contributes to the overall calibration accuracy. This segmentation allows the system to achieve comprehensive calibration coverage through distributed simple detectors rather than a single complex detector.
Data Source
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AI summary
Systems and methods for calibrating and controlling leaves of a multi-leaf collimator are disclosed. According to an exemplary method, a controller may receive images of collimator leaves and may determine a minor offset between an imaging marker and the tip of the respective leaf. In addition, the controller may quantify a barrel distortion effect associated with a leaf-imaging camera. The controller may correct leaf position data using the minor offsets and barrel distortion quantification, and may use the corrected leaf positions to accurately place the leaves during radiotherapy. Advantageously, a desired beam shaping window may be formed with the leaves, ensuring that healthy tissue is minimally irradiated while also ensuring that the target tissue receives the correct radiation dose. Embodiments of the present disclosure provide collimator calibration techniques which may be faster than prior calibration techniques, allowing shortened calibration times and faster radiotherapy sessions.