Overlapping Ripple Filter Members for Compact Particle Beam Irradiation
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Solution Overview
Problem
The existing particle beam irradiating devices face a challenge in maintaining a long distance between the irradiation unit and the patient due to uneven scattering of the charged particle beam after passing through conventional ridge filters, which complicates the setup and increases the overall size of the system.
Innovation Solution
An energy modulating device using a ripple filter composed of multiple overlapping filter members with openings, each with shifted positions and angles, to randomize the energy loss of the charged particle beam, thereby reducing the distance required between the irradiation unit and the patient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional ridge filter is used to form energy distribution, then the Bragg peak width is increased, but uneven scattering of the charged particle beam occurs and the distance between the irradiation unit and patient must be increased
Solution Approach 1:
The ridge filter is divided into multiple filter members (first filter member and second filter member) that are arranged in an overlapping manner. Each filter member has rod-shaped bodies with stepped portions, but they are positioned at different locations and orientations. This segmentation allows the beam to undergo multiple scattering events with different path lengths, randomizing the scattering pattern and reducing unevenness while maintaining the required Bragg peak width.
Solution Approach 2:
The filter members are arranged asymmetrically with respect to each other - the rod-shaped bodies in different filter members are positioned at different locations and have different orientations. This asymmetric arrangement ensures that the charged particle beam encounters varying thicknesses of material in different regions, creating a randomized scattering effect that eliminates the uniform unevenness produced by a single symmetric ridge filter.
2Reliability
If the distance between the patient and irradiation field forming device is increased to reduce scattering unevenness, then the system size becomes larger and setup becomes more complex
Solution Approach 1:
By dividing the ridge filter into multiple overlapping filter members, the scattering process is distributed across multiple interaction points. This allows uniform scattering to be achieved in a compact configuration, eliminating the need for large distances between the irradiation unit and patient, thereby simplifying system setup and reducing overall device complexity.
Solution Approach 2:
Multiple filter members are merged into a single overlapping arrangement where the first and second filter members occupy partially overlapping spatial regions. This combining of multiple scattering elements in a compact overlapping structure achieves the scattering uniformity that would otherwise require a large separation distance, thus reducing system complexity.
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 effectively reduces the distance between the irradiation unit and the patient, enhances the uniformity of the dose distribution, and increases the high dose region (Bragg peak) while maintaining a compact system design.
Implementation Method 1
unevenness occurs in scattering of the charged particle beam after passing through the ridge filter
Data Source
AI summary
Provided are a particle beam irradiating device capable of reducing a distance between an irradiation field forming device of the particle beam irradiating device and a patient, as well as an energy modulating device used for the particle beam irradiating device. The energy modulating device, i.e. a ripple filter 7, used for the particle beam irradiating device 10 that transports, by a beam transport line 2, a charged particle beam extracted from an accelerator 1 and delivers the charged particle beam by a scanning method using scanning magnets 4 and 5. The energy modulating device, i.e. the ripple filter 7, includes a filter member 70 having a plurality of openings 72 which penetrate the filter member 70 in a thickness direction and through which at least a part of the charged particle beam passes, in which the filter member 70 is one of two or more filter members overlapped in the thickness direction.