Photon Source Model Function for Medical Linear Accelerator Dose Calculation
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Solution Overview
Problem
Current methods for constructing photon source models for medical linear accelerators in radiation therapy are inadequate, as they fail to accurately describe photon fluence distribution and momentum direction information, leading to calculation errors and inefficiencies in dose calculation, especially in complex radiation fields.
Innovation Solution
A new method is introduced that separates primary and scattered ray photons, constructing separate source model functions for each, using fluence distribution and probability functions to accurately represent photon emission and absorption by the flattening filter, allowing for a more precise and efficient calculation of photon fluence and momentum direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase space file is used to record photon information, then calculation accuracy is improved, but file size becomes excessively large and storage space is occupied
Solution Approach 1:
The patent creates a simplified mathematical model (copy) of the phase space file that reproduces the essential photon distribution characteristics without storing all the detailed particle information. This model function captures the statistical properties and spatial-momentum distribution of photons, providing sufficient accuracy for dose calculation while occupying minimal storage space.
Solution Approach 2:
The patent transforms the phase space file from a detailed particle-by-particle representation into a parameterized mathematical model. By fitting the photon distribution data to analytical functions with a small number of parameters, the system maintains calculation accuracy while dramatically reducing the data quantity from billions of particle records to a compact set of model parameters.
2Measurement precision
If phase space file is used to record photon information, then calculation accuracy is improved, but calculation time increases due to time-consuming data import
Solution Approach 1:
The patent performs preliminary fitting of the phase space data to a mathematical model during the treatment planning stage. Once the model function is established, it can be directly used for dose calculations without repeatedly importing large phase space files. This preliminary action eliminates the time-consuming data import process while maintaining calculation accuracy.
Solution Approach 2:
Instead of repeatedly reading and processing the original phase space file, the system creates a lightweight mathematical model that replicates the essential characteristics. This model can be quickly loaded and used for multiple dose calculations, significantly reducing computation time while preserving the accuracy benefits of the detailed phase space data.
3Measurement precision
If phase space file is used, then photon fluence distribution is accurately recorded, but statistical variance is transmitted to dose calculation process
Solution Approach 1:
The patent transforms the discrete particle fluence data into a continuous parameterized model. By fitting analytical functions to the phase space data, the system smooths out statistical fluctuations and variations. The model parameters represent average distributions, eliminating the random statistical variance inherent in discrete particle simulations while preserving the essential fluence distribution characteristics.
4Measurement precision
If phase space file is formed, then photon information is fixed, but adaptability to different irradiation fields is reduced
Solution Approach 1:
The patent creates a dynamic mathematical model that can be re-fitted for different irradiation fields and treatment scenarios. Unlike a fixed phase space file, the model function parameters can be adjusted and re-optimized for various field sizes, energies, and configurations. This dynamic approach maintains accurate photon information representation while providing flexibility to adapt to different clinical requirements.
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 reduces modeling parameters, enhances calculation accuracy, and improves computational efficiency by faithfully reproducing photon distribution information, minimizing statistical fluctuations and storage requirements.
Implementation Method 1
calculating and tracking an interaction between the electrons and target atoms, bremsstrahlung photons generated during interaction
Implementation Method 2
a process that the bremsstrahlung photons are trimmed by a flattening filter
Implementation Method 3
tracking the electrons and target atoms, bremsstrahlung photons generated during interaction
Data Source
AI summary
A method for constructing a photon source model function of a medical linear accelerator, for calculating the dose of rays in a radiation therapy scheme is disclosed. A source model of a therapeutic photon beam of the accelerator includes a primary ray photon source model and a scattered ray photon source model. Physical parameters in the two parts of source model functions include the position coordinates of an emission point of a particle, a projection value of a unit momentum vector in a three-dimensional orthogonal direction, and the energy of the particle. By utilizing the model functions, photon fluence information, energy spectrum information, and unit momentum direction information of photons on any phase space plane can be accurately calculated. The method and thought for constructing the source model are applicable to construction of source models of photon beams with various nominal energies of the accelerator used in a radiation therapy.