Variable Thickness Diaphragm for Radiotherapy Collimation
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Solution Overview
Problem
The existing radiotherapy collimation systems, particularly those using multi-leaf collimators, face challenges in achieving precise beam shaping and minimizing radiation exposure to healthy tissues due to the weight and mass distribution issues of thick diaphragms, which lead to structural deformation and reduced accuracy during arc movements.
Innovation Solution
A radiotherapy apparatus featuring a diaphragm with a variable thickness, including a central spine region and thinner lateral sections, allowing for reduced mass while maintaining effective beam blocking, and a control system to extend multi-leaf collimator leaves to shadow regions blocked by the thinner diaphragm sections, optimizing beam shaping and reducing weight-related inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick diaphragm is used to block the radiation beam completely, then beam blocking efficacy is improved, but weight and mass increase causing structural deformation and reduced accuracy
Solution Approach 1:
The diaphragm employs variable thickness design where the central spine region has greater thickness (e.g., 8cm) for effective beam blocking, while lateral sections have reduced thickness (e.g., 2cm) to minimize weight. This local differentiation maintains blocking efficacy where needed while reducing overall mass to prevent structural deformation during arc movements.
Solution Approach 2:
The diaphragm is divided into functionally distinct regions: a central spine region for primary beam blocking and thinner lateral sections for reduced weight. This segmentation allows each region to be optimized for its specific function - the spine provides structural blocking while lateral sections minimize mass, resolving the contradiction between blocking efficacy and weight reduction.
2Reliability
If a thick diaphragm is used to ensure sufficient opacity for beam blocking, then shielding effect is improved, but device complexity increases due to heavier mechanisms
Solution Approach 1:
The diaphragm uses local quality differentiation where only the central spine region requires full thickness (8cm) for adequate shielding, while lateral sections use reduced thickness (2cm). This reduces the overall material quantity and mechanism complexity while maintaining sufficient shielding effect in the critical central area where beam blocking is most important.
3Ease of manufacture
If uniform thickness diaphragm is used to simplify manufacturing, then ease of manufacture is improved, but weight distribution causes structural deformation during arc movement
Solution Approach 1:
The diaphragm employs local quality variation with the central spine region having greater thickness (8cm) for structural integrity and beam blocking, while lateral sections have reduced thickness (2cm) to reduce weight. This non-uniform design prevents structural deformation during arc movements by optimizing weight distribution, though it may increase manufacturing complexity slightly.
4Manufacturing precision
If multi-leaf collimator leaves are extended to shadow regions blocked by thinner diaphragm sections, then beam shaping precision is improved, but device complexity increases
Solution Approach 1:
The variable thickness diaphragm design allows thinner lateral sections to be effectively shadowed by extended multi-leaf collimator leaves, enabling precise beam shaping in those regions. The control system coordinates leaf extension with the thinner diaphragm sections to achieve accurate beam contours, improving shaping precision while managing system complexity through coordinated control.
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
The solution enables precise beam shaping with minimal mass, reducing structural deformation and improving treatment accuracy by distributing weight more evenly, allowing for more complex and accurate radiation delivery without compromising beam blocking efficacy.
Implementation Method 1
a multi-leaf collimator for selectively limiting the width of the beam in at least the first direction
Implementation Method 2
a block collimator for selectively limiting the width of the beam in at least the second direction, the block collimator comprising a diaphragm moveable into and out of the beam and having a thickness in the direction of the beam axis that varies
Data Source
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AI summary
A radiotherapy apparatus comprises a means for producing a beam of radiation directed along a beam axis and having a width in first and second directions transverse to the beam axis, a multi-leaf collimator for selectively limiting the width of the beam in at least the first direction, a block collimator for selectively limiting the width of the beam in at least the second direction, the block collimator comprising a diaphragm moveable into and out of the beam and having a thickness in the direction of the beam axis that varies. The diaphragm can have a front edge of greater thickness than at least one region behind the front edge. It can also have a spine region extending from a rear part thereof towards the front edge that is greater thickness than at least one region displaced laterally with respect thereto. Together, these can cover the areas that will not be fully shadowed by a dynamically moving MLC. A control means for the multi-leaf collimator can be arranged to extend leaves of the multi-leaf collimator to shadow regions of the beam that are blocked by a relatively thinner section of the diaphragm. This is made easier if the spine region extends from the rearmost part of the diaphragm, the spine region extends to the front edge of the diaphragm, the spine region is straight, the spine region is a central region of the diaphragm, and if the width of the spine region increases towards the front edge of the diaphragm. The present invention also relates to a radiotherapy apparatus comprising a multi-leaf collimator and a block collimator, the block collimator comprising a diaphragm with variable thickness, and to a block collimator for use in radiotherapy apparatus comprising a diaphragm moveable into and out of a beam, and having a thickness in the direction of the beam axis that varies.