Multi-Leaf Collimator Carriage Synchronization for Dynamic Radiotherapy
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Solution Overview
Problem
Multi-leaf collimators face limitations in maximum aperture size due to leaf length constraints, which restrict the volume that can be treated, and existing solutions do not effectively enhance leaf speed or carriage movement to improve radiation delivery efficiency during dynamic treatments.
Innovation Solution
A multi-leaf collimator design where a carriage is mounted on a substrate, allowing independent movement of leaves relative to the carriage and the carriage relative to the substrate, with a control apparatus that synchronizes leaf and carriage positions to increase overall movement speed and reduce tracking errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If leaves are made longer to increase aperture size, then the volume that can be treated increases, but the reliability of driving the leaf deteriorates due to difficulties in driving long leaves reliably
Solution Approach 1:
The patent divides the leaf motion function into two independent segments: the carriage moves along the treatment arc to provide the primary positioning, while the leaves move only to provide the fine adjustment and modulation. This segmentation allows the carriage to handle the bulk of the motion range, enabling longer effective aperture without requiring excessively long leaves.
Solution Approach 2:
The patent introduces a second degree of freedom by adding the carriage motion dimension. Instead of relying solely on leaf length in one dimension, the system uses combined carriage position and leaf position in two dimensions to achieve the same effective aperture, resolving the contradiction between aperture size and driving reliability.
2Productivity
If leaf speed is increased to reduce treatment time during dynamic delivery, then productivity increases, but the complexity of the drive system increases due to the need for high-speed precise control
Solution Approach 1:
The patent segments the speed requirement between two components: the carriage provides the bulk of the speed for traversing the treatment arc, while the leaves provide only the fine adjustment speed. This segmentation allows each component to be optimized independently, reducing the overall system complexity while maintaining high productivity.
3Adaptability or versatility
If carriage repositioning is performed to enable leaves to reach new positions, then adaptability increases, but discontinuities arise during dynamic radiation delivery that affect treatment smoothness
Solution Approach 1:
The patent uses preliminary action by continuously pre-positioning the carriage in anticipation of future leaf position requirements. The control system calculates optimal carriage positions in advance and smoothly transitions between them, preventing discontinuities before they occur and maintaining stable, continuous delivery.
Data Source
AI summary
A multi-leaf collimator for a radiotherapy apparatus comprises a plurality of elongate leaves mounted in a carriage, the carriage being mounted on a substrate, wherein the leaves are independently moveable relative to the carriage in a longitudinal direction, and the carriage is moveable in that direction relative to the substrate, and a control apparatus is arranged to receive a signal representing leaf positions relative to the substrate and to control the leaf positions relative to the carriage and the carriage positions relative to the substrate so as to achieve those leaf positions relative to the substrate. Most MLCs sense the current positions of the leaves relative to the substrate. The control apparatus can therefore compare the current leaf positions to the signaled leaf positions, and move the leaves and the carriage accordingly. A corresponding method is also disclosed.