Scanning Electromagnet Hysteresis Correction in Particle Beam Therapy
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Solution Overview
Problem
The hysteresis characteristics of scanning electromagnets in particle beam therapy systems lead to inaccuracies in beam irradiation, as the magnetic field at increasing current differs from that at decreasing current, affecting the accuracy of irradiation positions and doses, and existing methods struggle to accurately correct for these effects and detect beam positions in real-time.
Innovation Solution
A scanning power source and irradiation control apparatus with a scanning electromagnet command value learning generator that evaluates and updates the excitation current command values based on run-through results to eliminate hysteresis effects, ensuring high-accuracy beam irradiation in raster-scanning and hybrid scanning methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scanning electromagnets are used to perform raster-scanning or hybrid scanning for particle beam irradiation, then the irradiation process becomes continuous and efficient, but hysteresis characteristics cause inaccuracies in beam irradiation position and dose
Solution Approach 1:
The system performs a run-through (preliminary irradiation) before actual treatment to acquire accurate relationship data between scanning electromagnet command values and actual beam positions. This preliminary action captures hysteresis effects and creates a correction map that is stored and applied during subsequent irradiations, eliminating accuracy problems without sacrificing treatment efficiency
Solution Approach 2:
The system uses beam position detectors to measure actual beam positions during the run-through and feeds this information back to create a correction map. The correction map stores the relationship between command values and actual positions, including hysteresis effects. During treatment, this feedback mechanism allows real-time correction of command values to compensate for hysteresis, maintaining both efficiency and accuracy
2Manufacturing precision
If existing correction methods are used to account for hysteresis, then some accuracy improvement is achieved, but the methods struggle to accurately detect beam positions in real-time and correct for hysteresis effects
Solution Approach 1:
The system performs a preliminary run-through to accurately map the relationship between command values and actual beam positions under identical conditions to actual treatment. This preliminary measurement captures real hysteresis behavior and detection characteristics, creating an accurate correction model that works reliably during subsequent treatments without requiring real-time detection during actual irradiation
Solution Approach 2:
The system creates a correction map that copies and stores the relationship between command values and actual beam positions from the run-through. This correction map serves as a lookup table that provides accurate position information without requiring complex real-time detection during treatment. The correction map effectively replicates the beam position behavior for any given command value, including hysteresis effects
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 solution effectively eliminates the hysteresis effect, enabling high-accuracy and high-safety particle beam irradiation by learning and adjusting the excitation current command values, thereby improving the precision of beam positioning and dose administration.
Implementation Method 1
a scanning electromagnet that performs scanning with a charged particle beam transported by the beam transport apparatus (53)
Implementation Method 2
The hysteresis characteristics of scanning electromagnets in particle beam therapy systems lead to inaccuracies in beam irradiation, as the magnetic field at increasing current differs from that at decreasing current
Data Source
AI summary
A scanning power source that outputs the excitation current for a scanning electromagnet and an irradiation control apparatus that controls the scanning power source; the irradiation control apparatus is provided with a scanning electromagnet command value learning generator that evaluates the result of a run-through, which is a series of irradiation operations through a command value for the excitation current outputted from the scanning power source, that updates the command value for the excitation current, when the result of the evaluation does not satisfy a predetermined condition, so as to perform the run-through, and that outputs to the scanning power source the command value for the excitation current such that its evaluation result has satisfied the predetermined condition.