Ion Radiotherapy Scattering Model Segmentation
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Solution Overview
Problem
Conventional methods for modeling proton multiple scattering in radiotherapy, such as the Goudsmit-Saunderson theory, fail to accurately account for both Coulomb and nuclear elastic scattering, leading to incorrect dose distribution predictions, especially at larger angles.
Innovation Solution
A computer-based method that restricts the Goudsmit-Saunderson theory to Coulomb scattering angles up to a cut-off point, then adds nuclear elastic scattering contributions for larger angles, using experimental data or models to ensure a consistent formalism based on fundamental differential cross-sections, avoiding double counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the Goudsmit-Saunderson theory is used to model multiple scattering, then the model is simple and computationally efficient, but it only accounts for Coulomb scattering and produces incorrect results at large scattering angles
Solution Approach 1:
The scattering angle range is segmented into two intervals: a first angular interval for Coulomb scattering (small angles) and a second angular interval for nuclear elastic scattering (large angles). This segmentation allows each model to be applied within its valid range, improving overall accuracy without requiring a completely new complex model.
Solution Approach 2:
The patent introduces a cut-off angle parameter to distinguish between Coulomb and nuclear scattering regimes. By changing the parameter (scattering angle) threshold, the appropriate physical model is selected for each angular range, enabling accurate prediction across the full angular spectrum.
2Productivity
If conventional multiple scattering theories are used, then calculations are computationally efficient, but they fail to account for both Coulomb and nuclear forces simultaneously
Solution Approach 1:
The calculation process is segmented into two distinct computational paths based on scattering angle. For angles below the cut-off, efficient Coulomb scattering calculations are performed; for angles above, nuclear elastic scattering calculations are performed. This maintains computational efficiency while improving reliability.
Solution Approach 2:
The cut-off angle acts as an intermediary parameter that mediates between the two scattering models. It determines which model is active for each scattering event, allowing both Coulomb and nuclear force effects to be accounted for in the overall dose calculation without requiring a single complex unified model.
3Measurement precision
If nuclear elastic scattering is included for all angles, then large angle scattering is accurately modeled, but it leads to double counting when combined with Coulomb scattering models
Solution Approach 1:
The angular range is segmented with a clear boundary (cut-off angle) that prevents overlap between Coulomb and nuclear scattering applications. This segmentation eliminates double counting by ensuring each scattering mechanism is applied to non-overlapping angular intervals, maintaining model consistency.
Solution Approach 2:
Instead of applying one model across all angles and adding corrections, the patent inverts the approach by applying different models to different angular ranges from the start. This prevents the double counting problem that arises when attempting to combine full-angle Coulomb models with nuclear scattering corrections.
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 provides a reliable model for proton multiple scattering, reducing errors in dose deposition and improving the accuracy of dose distribution predictions by correctly accounting for both Coulomb and nuclear forces, particularly at larger scattering angles.
Implementation Method 1
The elastic scattering of a proton on a nucleus is caused by the combined effect of two forces: the Coulomb force and the strong nuclear force. The Coulomb scattering between a proton and a nuclei is caused by electro-magnetic interaction between their electrical charges.
Implementation Method 2
The nuclear elastic scattering is caused by direct interaction between the proton and the nuclei through the strong force.
Implementation Method 3
A proton that passes through tissue undergoes of the order of millions elastic scattering interactions per centimetre of tissue. In radiotherapy calculations of, for example, dose the elastic scattering interactions are usually incorporated through so called multiple scattering theories.
Data Source
AI summary
A method of evaluating a radiotherapy treatment plan for ion based radiotherapy, is proposed, comprising the steps ofdetermining multiple elastic scattering of ions for scattering angles in a first angular interval having an upper limit at a selected cut-off angle by means of a model for Coulomb scattering;determining multiple elastic scattering of ions for scattering angles in a second angular interval having a lower limit at the selected cut-off angle;determining the scattering for angles in a range comprising at least a part of the first angular interval and at least a part of the second angular interval, based on the results obtained for the first and second angular interval, respectively.The method avoids the double counting of particles at large scattering angles that occurs when using conventional methods.