Gantry MRI Magnetic Pole Cavities for Accurate Particle Beam Therapy
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Solution Overview
Problem
The existing particle therapy systems face challenges in accurately measuring the target position and evaluating the position and dose of the particle beam due to strong magnetic fields, which affect the arrangement and accuracy of the particle beam monitor and MRI apparatus, leading to complications in forming a conformal dose distribution amidst respiratory motion of the irradiation target.
Innovation Solution
A particle therapy system is designed with a gantry-mounted MRI apparatus featuring a magnetic circuit with an iron core and coils, where the iron core has oppositely disposed magnetic poles with cavities, allowing the particle beam to pass through and minimizing the magnetic field leakage, enabling accurate positioning and dosing measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an iron core is added to the MRI apparatus to reduce leakage magnetic field, then the magnetic field structure becomes simpler and equipment arrangement becomes easier, but the particle beam may be affected by electromagnetic force causing orbit deviation
Solution Approach 1:
The patent extracts the harmful magnetic field interaction by removing the particle beam from the region where the iron core generates strong magnetic flux. The beam passage is specifically positioned to avoid the high-density magnetic field zones near the iron core, allowing the iron core to reduce leakage without significantly affecting the beam orbit.
Solution Approach 2:
The patent introduces a non-magnetic beam passage as an intermediary structure that allows the particle beam to pass through the MRI apparatus without interacting with the iron core's magnetic field. This mediator structure enables both the iron core to function for reducing leakage and the beam to maintain its orbit accuracy.
2Measurement precision
If the MRI apparatus is installed in the gantry to enable real-time target position measurement, then measurement accuracy is improved, but the leakage magnetic field is strengthened making it difficult to arrange the particle beam monitor
Solution Approach 1:
The patent extracts the harmful leakage magnetic field by introducing an iron core that channels and contains the magnetic flux within the MRI apparatus. This extraction of the magnetic field into a controlled path allows the particle beam monitor to be arranged in regions where the magnetic field strength is significantly reduced, making the system configuration feasible.
3Measurement precision
If the particle beam monitor is placed close to the patient for accurate dose measurement, then measurement accuracy is improved, but the strong magnetic field causes difficulty in arranging the monitor
Solution Approach 1:
The patent extracts and contains the strong magnetic field within the MRI apparatus using an iron core, creating a low-magnetic-field zone outside the MRI where the particle beam monitor can be conveniently arranged close to the patient. This allows accurate dose measurement without the monitor being subjected to the strong magnetic field that would complicate its arrangement.
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
This configuration allows for high-accuracy measurement of the target position and particle beam dose while reducing the complexity of the magnetic field structure, enabling precise and efficient irradiation of the particle beam, even in the presence of respiratory motion.
Implementation Method 1
an MRI apparatus (50) which rotates together with the gantry (18). The MRI apparatus (50) includes a magnetic circuit having an iron core (60) and a plurality of coils (61) serving as a magnetic flux source
Implementation Method 2
the particle therapy system measures the target position using the MRI installed in the gantry rotating around the patient
Implementation Method 3
a particle beam monitor for measuring a position and an irradiation dose of the particle beam
Implementation Method 4
an accelerator which generates a charged particle beam for extraction
Implementation Method 5
The charged particle beam passing through the cavity is irradiated to the irradiation target
Data Source
AI summary
A particle therapy system includes an accelerator 1 which generates a particle beam for extraction, an irradiation apparatus 21 which irradiates the particle beam to an irradiation target 26, a gantry 18 which rotates together with the irradiation apparatus 21, and an MRI apparatus 50 which rotates together with the gantry 18. The MRI apparatus 50 includes a magnetic circuit composed of an iron core 60 and a plurality of coils 61 serving as a magnetic flux source. The iron core 60 includes two oppositely disposed magnetic poles 63A and 63B, and a return yoke 64 for connecting the magnetic poles 63A and 63B. The magnetic poles 63A, 63B have cavities 65A, 65B. The particle beam passing through the cavity 65A is irradiated to the irradiation target 26.