Gantry Wheel Adjustment for Proton Beam Alignment
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Solution Overview
Problem
Proton therapy systems face challenges in maintaining proper alignment between the proton delivery nozzle and the gantry's axis of rotation due to deflection caused by fabrication tolerances and the size/weight of gantry components, leading to inaccuracies in proton beam targeting and prolonged setup times.
Innovation Solution
A gantry apparatus with adjustable bearings and a bearing surface that allows the gantry wheel to be raised or lowered as it rotates, maintaining proton beam alignment by adjusting cam followers and hydraulic actuators to compensate for deflection, and using a method to estimate and correct nozzle-trajectory errors at various angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gantry is constructed with large magnets and heavy components to direct protons, then the proton beam can be directed accurately, but the structure deflects when rotated at different angles, causing the system center to drift above target accuracy
Solution Approach 1:
The system pre-calculates and stores correction values for gantry center drift at various rotation angles before treatment begins. During operation, the appropriate correction value is retrieved and applied based on the current gantry angle, eliminating the need for real-time compensation and maintaining consistent targeting accuracy throughout rotation.
Solution Approach 2:
The system dynamically adjusts the proton beam parameters (energy, angle, position) based on the gantry rotation angle to compensate for structural deflection. By changing these parameters in real-time according to the measured or pre-calculated drift, the system maintains accurate targeting despite the heavy structure's tendency to deflect.
2Measurement precision
If the patient bed is moved to compensate for beam misalignment at different rotation angles, then alignment can be maintained, but the treatment process becomes time-consuming and complicated
Solution Approach 1:
The system pre-calculates correction values for beam misalignment at all possible gantry angles before treatment begins. These corrections are stored and automatically applied during treatment based on the current angle, eliminating the need for time-consuming patient repositioning and allowing continuous treatment across all angles.
Solution Approach 2:
The system replaces the mechanical solution of moving the patient bed with a computational solution that adjusts beam parameters and gantry positioning through software control. This substitution eliminates the time-consuming mechanical repositioning operations while maintaining alignment accuracy through digital correction algorithms.
3Measurement precision
If traditional gantry construction methods are used with large magnets, then proton beam direction is achieved, but it takes about 6 months to build and 12 months to commission the equipment
Solution Approach 1:
The gantry system is divided into modular segments that can be manufactured separately and assembled more quickly. This segmentation allows for parallel manufacturing processes and reduces the overall construction time while maintaining the necessary beam direction capabilities through coordinated operation of the modular components.
Solution Approach 2:
The system uses advanced manufacturing parameters and materials that reduce construction time while maintaining beam direction precision. By optimizing parameters such as magnet size, material properties, and structural dimensions, the system achieves the required performance with a more compact and faster-to-build configuration.
Data Source
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AI summary
A gantry wheel adjustment system and method to adjust a gantry wheel of a proton treatment system, including an estimation unit to estimate a bearing adjustment value for each of the adjustable bearings based on a stiffness parameter of each adjustable bearing, the stiffness parameter being a function of a force applied at each adjustable bearing and a deflection of the gantry wheel associated with the force applied at each adjustable bearing, the bearing adjustment value corresponding to a nominal position value for each adjustable bearing to compensate for gantry wheel flexing when the gantry wheel is rotated from a first angular positon to a second angular position, the adjustable bearings being configured to support the gantry wheel on the bearing surface and maintain the proton beam at the isocenter of the gantry wheel during gantry wheel rotation.