Magnetoresistive Sensor Position Detection for Radiation Therapy Collimators
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Solution Overview
Problem
Current radiation-tolerant position sensors for multileaf collimators in radiation therapy systems face issues with repeatability and reliability due to wear over time and gravity-related inaccuracies, affecting the precision of beam shaping and dosing in radiation therapy.
Innovation Solution
The use of magnetoresistive sensors to measure the rotational position of a multileaf collimator carousel, which detects ferromagnetic teeth on a toothed ring, providing precise and reliable position information for improved beam shaping and dosing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical position sensors are used to measure MLC and MLC leaf positions, then the system can achieve position measurement functionality, but the sensors experience wear over time leading to reduced repeatability and reliability
Solution Approach 1:
The patent replaces electromechanical position sensors with magnetoresistive sensors that use magnetic field detection instead of mechanical contact. The magnetoresistive sensor detects the position of ferromagnetic teeth on a toothed ring through magnetic field interaction, eliminating mechanical wear and contact friction while maintaining position measurement capability throughout the sensor's operational life
2Measurement precision
If electromechanical position sensors are positioned at certain angles to measure MLC position, then the system can obtain position data, but gravity-related inaccuracies affect measurement precision
Solution Approach 1:
The patent eliminates gravity-related measurement errors by replacing electromechanical sensors with magnetoresistive sensors that measure position through magnetic field interactions rather than mechanical contact. The magnetoresistive sensor detects tooth position on the rotating carousel through magnetic field changes, providing accurate measurements independent of gravitational effects or sensor orientation
3Reliability
If magnetoresistive sensors are used to detect ferromagnetic teeth on the carousel, then wear-based inaccuracies are reduced, but the system complexity increases due to the need for toothed ring integration
Solution Approach 1:
The patent introduces a toothed ring with ferromagnetic teeth as an intermediary element between the rotating MLC carousel and the magnetoresistive sensor. This toothed ring serves as a mechanical encoder that converts rotational position into magnetic field variations, which the magnetoresistive sensor then detects electronically, simplifying the overall system architecture while maintaining high reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the precision and reliability of multileaf collimator positioning, reducing wear-based inaccuracies and ensuring accurate beam shaping and dosing, thereby improving the effectiveness of radiation therapy.
Implementation Method 1
a magnetoresistive sensor configured to detect the ferromagnetic teeth of a toothed ring coupled to a surface of the carousel
Data Source
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AI summary
A method of measuring a rotational position of an assembly with circumferential ferromagnetic teeth includes applying (1302) an excitation signal for a cycle to an actuator, the cycle causing a first rotational displacement of a first ferromagnetic tooth from a first rotational position to a second rotational position and a second rotational displacement of a second ferromagnetic tooth from the second rotational position to a third rotational position. The method further includes measuring (1303) a plurality of first signal outputs from a magnetoresistive sensor during the cycle; determining one or more signal offset values based on the plurality of first signal outputs; applying the signal excitation for a portion of a second cycle to the actuator; measuring second signal outputs from the magnetoresistive sensor; generating (1304) corrected signals by modifying the second signal outputs with the signal offset values; and, based on the corrected signals, determining (1305) a rotational position of the assembly.