Magnetoresistive MLC Leaf Position Sensing Without Mechanical Wear
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Solution Overview
Problem
Current position sensors for multileaf collimators in radiation therapy systems suffer from repeatability and reliability issues due to wear over time and gravity-related inaccuracies, affecting the precise positioning of leaves, which is crucial for accurate beam shaping and dosing in radiation therapy.
Innovation Solution
The use of magnetoresistive sensors for both linear and rotational motion detection of multileaf collimator leaves, providing precise position information without mechanical contact and maintaining accuracy in high-radiation environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromechanical position sensors are used to measure MLC and MLC leaf positions, then position detection is achieved, but repeatability and reliability deteriorate due to wear over time
Solution Approach 1:
The patent replaces electromechanical position sensors with a magnetic field-based detection system. Magnets are attached to MLC leaves and detected by magnetoresistive sensors, eliminating mechanical contact and wear. This substitution of mechanical sensing with magnetic field sensing resolves the contradiction by maintaining measurement precision while significantly improving reliability through contactless operation.
Solution Approach 2:
The patent introduces magnets as an intermediary between the MLC leaves and the detection system. Instead of direct mechanical sensing, the magnetic field serves as a mediator that transmits position information from the leaves to the magnetoresistive sensors without physical contact, thereby eliminating wear-related reliability issues while preserving measurement accuracy.
2Measurement precision
If electromechanical position sensors are positioned at certain angles, then position measurement is possible, but accuracy deteriorates due to gravity-related inaccuracy
Solution Approach 1:
The patent replaces gravity-sensitive electromechanical sensors with magnetoresistive sensors that detect magnetic field positions. Since magnetic field detection is not influenced by gravitational forces, this substitution eliminates gravity-related inaccuracies while maintaining position measurement precision across various angles.
Solution Approach 2:
The patent changes the detection parameter from mechanical position sensing to magnetic field position sensing. This parameter change transforms the measurement mechanism from one susceptible to gravitational effects into one that operates independently of gravity, thereby eliminating angle-dependent accuracy deterioration.
3Measurement precision
If magnets are disposed on MLC leaves for position detection, then linear and rotational motion detection is enabled, but device complexity increases
Solution Approach 1:
The patent implements a multi-functional magnetic detection system where the same magnets and magnetoresistive sensors serve multiple purposes: detecting both linear and rotational motion of MLC leaves. This universal approach enables comprehensive motion detection without proportionally increasing system complexity, as a single magnetic field detection mechanism handles multiple measurement tasks.
Solution Approach 2:
The patent combines linear and rotational position detection into a unified magnetic field-based system. By merging these detection functions into a single coherent approach using magnets and magnetoresistive sensors, the system achieves comprehensive motion detection while avoiding the complexity of separate mechanical sensing mechanisms for each motion type.
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
Ensures accurate and reliable positioning of multileaf collimator leaves, meeting International Electrotechnical Commission requirements, thereby enhancing the precision and safety of radiation therapy treatments.
Implementation Method 1
magnetoresistive sensors for both linear and rotational motion detection of multileaf collimator leaves
Data Source
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AI summary
A multileaf collimator includes a plurality of movable leaves (351) for shaping a radiotherapy beam, wherein each leaf is independently movable in a same linear travel direction. Each leaf includes a linear array (720) of magnets (721) disposed on a measurement surface of the leaf and an array of magnetoresistive sensors (651) that is disposed proximate the measurement surfaces of the leaves.