Ion Beam Energy Filter for Uniform Dose Distribution
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Solution Overview
Problem
Existing charged particle irradiation systems face challenges in maintaining uniform dose distribution when the irradiation target moves, such as due to patient breathing, leading to potential interruptions and inefficiencies in the scanning and energy change methods.
Innovation Solution
Incorporating an energy filter and repainting irradiation techniques to form a mild bragg peak shape and ensure continuous one-plane irradiation without interruption, allowing for stable dose distribution even with target movement, by using a wedge-shaped energy filter to expand the bragg peak and reduce fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scanning irradiation method is used to widen dose distribution, then ion beam energy loss is reduced and efficiency is improved, but uniform dose distribution cannot be formed when irradiation target is displaced
Solution Approach 1:
The system performs preliminary actions by completing one-plane irradiation without interruption before the target displacement becomes significant, and by pre-planning repainting irradiation sequences to compensate for anticipated target movement during the irradiation process
Solution Approach 2:
The system implements periodic repainting irradiation where the ion beam scans the same irradiation field multiple times with adjusted parameters between cycles, allowing the target to return to a reference position or compensating for cumulative displacement through repeated dosing patterns
2Manufacturing precision
If repainting irradiation is performed with interruption when displacement waveform changes, then dose distribution accuracy is maintained, but irradiation time is extended
Solution Approach 1:
The system uses the target's own periodic motion characteristics (breathing cycle) to determine when to perform repainting irradiation, automatically synchronizing the irradiation interruptions with the natural return of the target to reference positions without requiring external intervention or extended waiting periods
Solution Approach 2:
The system changes irradiation parameters such as beam energy, scanning speed, and dose rate between repainting cycles to optimize the balance between maintaining dose accuracy and minimizing total irradiation time, adapting parameters based on real-time target position feedback
3Area of stationary object
If scanning magnet is used to scan ion beam in lateral direction, then dose distribution is widened, but irradiation uniformity is compromised when target moves during sequential painting
Solution Approach 1:
The system employs real-time feedback from target position monitoring to dynamically adjust scanning magnet parameters and beam delivery timing, ensuring that each repainting cycle compensates for measured displacements and maintains uniform dose distribution across the entire irradiation field
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 approach enables the formation of a uniform dose distribution in both lateral and depth directions, reducing the impact of target displacement and allowing for more efficient use of ion beam energy, with increased repainting irradiations and reduced treatment time.
Implementation Method 1
an energy filter 26 that filters an ion beam with a plurality of energies
Implementation Method 2
a peak of the dose distribution is called a bragg peak... By making a bragg peak shape mild using the energy filter
Implementation Method 3
the scanning magnet 23 scans the ion beam traveling therethrough... the scanning magnet controls an irradiation position of the ion beam
Implementation Method 4
a cancer or other affected part of a patient is irradiated with a charged particle beam (ion beam) of, for example, either a proton or carbon ion beam
Data Source
AI summary
In a charged particle irradiation system, forming a uniform dose distribution is required by irradiating a moving irradiation object through beam scanning and energy stacking. The charged particle irradiation system includes an ion beam generator 1 from which an ion beam is extracted with a target beam current value thereof set; an irradiation nozzle 21 having scanning magnets 23, 24 and an energy filter 26, the irradiation nozzle 21 for irradiating an irradiation object with the ion beam; and an irradiation object monitoring unit 66 for measuring a position of the irradiation object and outputting signals that vary with time according to displacement of the irradiation object. The charged particle irradiation system determines extraction timing of the ion beam based on the signal outputted from the irradiation object monitoring unit 66 and sequentially changes energies of the ion beam to thereby perform a repainting irradiation with each of the energies.