Charged Particle Beam Position Tuning With a Fixed Beam Stopper
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Solution Overview
Problem
Existing methods for tuning charged particle beam position in particle therapy apparatus are inadequate for high dose rate treatments like FLASH therapy, as they either require excessive tuning spot doses or complex, unreliable beam stop mechanisms, and fail to account for scanning magnet errors.
Innovation Solution
A particle therapy apparatus with a beam stopper positioned downstream of scanning magnets, allowing beam position detection and correction without moving the stopper, and a control system to adjust scanning magnets based on measured beam position deviations, ensuring accurate beam alignment for both conventional and high dose rate treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PBS tuning loop is used for FLASH therapy, then beam position can be tuned, but tuning spot dose becomes excessively high which lowers dose rate for PBS field and negates FLASH effect
Solution Approach 1:
The patent extracts the beam position measurement function from the treatment beam path by using a separate tuning beam directed to a tuning chamber. This separation allows position measurement without interfering with the therapeutic beam's dose rate, as the tuning beam operates independently and its dose is not subtracted from treatment spots.
Solution Approach 2:
The patent segments the beam path into separate functions: a tuning beam path for position measurement and a treatment beam path for therapy delivery. The tuning chamber is positioned at a location where it does not overlap with treatment fields, allowing independent operation without dose interference.
2Measurement precision
If mobile beam stop is used for retuning during treatment, then beam position can be corrected, but device complexity increases and reliability decreases due to moving parts subject to failures
Solution Approach 1:
Instead of moving the beam stop to achieve tuning, the patent inverts the approach by using a fixed beam stop and moving the beam itself to a dedicated tuning chamber. This eliminates the need for a mobile beam stop mechanism while achieving the same tuning objective.
Solution Approach 2:
The patent introduces a tuning chamber as an intermediary structure that facilitates beam position measurement without requiring movement of the beam stop. The tuning chamber serves as a dedicated measurement zone separate from the treatment path, eliminating mechanical complexity.
3Measurement precision
If tuning is performed before treatment with test irradiation, then beam position can be measured, but treatment time is lost due to separate calibration phase
Solution Approach 1:
The patent performs preliminary beam position tuning by directing the beam to the tuning chamber before treatment, but integrates this tuning data into the treatment planning process. The tuning is done in advance but does not require separate calibration time during treatment setup, as the tuning chamber measurement is quickly integrated into the treatment workflow.
4Object-affected harmful factors
If beam stop is moved to block beam during retuning, then patient safety is improved, but reliability decreases due to potential positioning failures and wrong dose delivery
Solution Approach 1:
The patent extracts the tuning measurement function from the patient treatment path by using a separate tuning chamber. This separation ensures patient safety without requiring a mobile beam stop, as the tuning beam is directed away from the patient area entirely, eliminating the reliability risks associated with beam stop positioning.
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 saves treatment time, enhances reliability and safety by eliminating stopper movement, and maintains dose accuracy during high dose rate treatments like FLASH therapy.
Implementation Method 1
a beam position detector arranged downstream of the scanning magnets and adapted to detect an X and Y position of the charged particle beam
Implementation Method 2
a beam stopper arranged downstream of the beam position detector, the beam stopper being adapted to stop the charged particle beam when it hits the beam stopper
Implementation Method 3
scanning magnets to scan the charged particle beam over the target
Data Source
AI summary
A particle therapy apparatus configured to scan a charged particle beam over a target according to a pre-defined treatment field which covers a treatment surface in an isocenter plane of the apparatus. The apparatus is capable of scanning the beam over a reachable surface which covers and is larger than the treatment surface. A beam stopper is arranged downstream of the scanning magnets of the apparatus, at a position to prevent the beam from reaching at least a portion of the reachable surface and to allow the beam to reach any portion of the treatment surface. A control system is configured to control the apparatus to direct the beam to the beam stopper and to meanwhile measure a position of the beam, to calculate a difference between a desired position and the measured position of the beam when directed to the beam stopper, and to scan the beam over the target according to the pre-defined treatment field by taking into account the calculated difference.