Proton Beam Scanning Correction for Magnetization Errors
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Solution Overview
Problem
Pencil beam scanning in proton therapy is sensitive to organ motion, leading to dose homogeneity issues due to high sensitivity to tumor movement during delivery, and existing systems face systematic errors from magnetization and eddy current effects, which affect beam position and energy changes, making precise volumetric repainting challenging.
Innovation Solution
A system and method that include a proton source, beam bending and focusing units, sweeper magnets, a position-sensitive detector, and control logic for beam steering and correction, utilizing generic and patient-specific dynamic corrections to minimize beam position errors and adapt to changing energy settings, incorporating self-teaching mechanisms to address unpredictable magnetization and eddy current effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If very fast energy changes are implemented for volumetric repainting, then scanning speed is improved, but systematic errors from magnetization and eddy current effects worsen beam position precision
Solution Approach 1:
The system performs preliminary measurements of beam position during fast energy changes and pre-calculates correction values before treatment delivery. This allows the control system to compensate for magnetization and eddy current effects in advance, maintaining beam position precision even during very fast scanning
Solution Approach 2:
The system continuously monitors actual beam position during fast energy changes and compares it with expected position. The measured deviations are fed back to the control system, which dynamically adjusts magnet currents to correct beam position errors in real-time, enabling both fast scanning and high precision
2Manufacturing precision
If pencil beam scanning is used for precise dose painting, then dose conformation to target shape is improved, but sensitivity to organ motion worsens dose homogeneity
Solution Approach 1:
The system implements periodic repainting of the target volume by delivering multiple passes of pencil beam scanning at different energy levels. This periodic repainting approach averages out the effects of organ motion during treatment, maintaining dose homogeneity while preserving the precision of dose conformation to target shape
Solution Approach 2:
The system dynamically adapts the scanning parameters including beam energy, spot intensity, and scanning speed during treatment delivery. This dynamic adjustment allows the system to compensate for organ motion in real-time, maintaining both dose conformation precision and dose homogeneity despite target movement
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 system achieves high precision in beam delivery, reducing systematic errors and improving flexibility, allowing for fast scanning with accurate dose distribution, even with moving targets, by automatically correcting beam position and energy changes, enhancing the precision of proton therapy.
Implementation Method 1
a number of proton beam bending and/or focusing units
Implementation Method 2
The beam is delivered into the patient as the sum of small physical pencil beams. The dose distribution is shaped in the lateral direction by scanning the beam by magnetic deflection using so-called sweeper magnets in the beam line upstream of the patient.
Implementation Method 3
a position-sensitive detector being aligned with the nozzle in order to control the position of the proton beam
Data Source
AI summary
A system and a method improve a quality of beam delivery in proton therapy by pencil beam scanning of a predeterminable volume within a patient that minimizes beam position errors. The system has a proton source generating a proton beam, a number of proton beam bending/focusing units, a beam nozzle having an outlet for the proton beam to penetrate the predetermined volume, a beam bending magnet, and a couple of sweeper magnets to sweep the proton beam in both lateral directions. A position-sensitive detector is aligned with the nozzle to control the position of the proton beam and control logic controls the position and the energy of the proton beam and has a beam steering data set. A correction logic is aligned with the control logic for correcting beam position errors by comparing an expected beam position with the actual beam position detected and generates beam position correction data.