Multi-Level MLC Design for Radiation Leakage Reduction
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Solution Overview
Problem
Conventional multileaf collimators (MLCs) face challenges in reducing radiation leakage and achieving high beam shaping resolution due to limitations in leaf thickness and construction, which can lead to underdose effects and increased bulk in radiation systems.
Innovation Solution
The implementation of a multi-level MLC design with two sets of beam blocking leaves in different planes, where leaves are offset and movable in parallel directions, allowing for improved beam shaping resolution and reduced leakage by eliminating the need for additional collimation jaws, thereby reducing system bulk and enhancing clearance between the patient and equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the width of leaves is reduced to improve MLC resolution, then beam shaping resolution is improved, but the drive screws become long and slender making them susceptible to column buckling
Solution Approach 1:
The patent introduces a second level of leaves disposed in a different plane from the first level, effectively adding a dimensional layer to the MLC structure. This multi-level arrangement allows for reduced leaf width at each level while maintaining overall structural integrity through the distributed configuration across multiple planes, thereby improving beam shaping resolution without compromising buckling resistance
Solution Approach 2:
The MLC is divided into multiple levels with separate sets of leaves, where each level can be independently structured and supported. This segmentation allows each level's drive system to handle shorter, stouter screws that are less prone to buckling, while the combined multi-level structure achieves the desired high resolution through the coordinated action of multiple narrower leaf sets
2Object-affected harmful factors
If conventional single level MLCs use tongue in groove designs to reduce leakage, then radiation leakage is reduced, but underdose effects occur when treatment fields are combined
Solution Approach 1:
By adding a second level of leaves in a different plane, the patent creates a three-dimensional leaf arrangement that provides radiation leakage blocking from multiple spatial perspectives. This multi-planar configuration reduces reliance on tongue-in-groove geometries and their associated underdose problems, as leaves at different levels provide overlapping protection that maintains dose accuracy when treatment fields are combined
3Object-affected harmful factors
If collimation jaws are added to reduce leakage between abutted leaf ends, then radiation leakage is reduced, but system bulk increases and clearance between patient and equipment is reduced
Solution Approach 1:
The second level of leaves extends the leakage mitigation capability into a different spatial plane, allowing the MLC to control radiation leakage between abutted leaf ends without requiring additional collimation jaws. This multi-level leaf arrangement provides the necessary leakage reduction while maintaining a more compact system volume and preserving clearance between the patient and moving equipment
Data Source
AI summary
A multilevel MLC includes a first set and a second set of a plurality of pairs of beam blocking leaves arranged adjacent one another. Leaves of each pair in the first set are disposed in an opposed relationship and longitudinally movable relative to each other in a first direction. Leaves of each pair in the second set are disposed in an opposed relationship and longitudinally movable relative to each other in a second direction generally parallel to the first direction. The first and second sets of pairs of leaves are disposed in different planes.