IMRT Illumination Distribution Layered Graph Optimization
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Solution Overview
Problem
Current methods for determining illumination distributions in intensity modulated radiation therapy (IMRT) often result in reduced quality due to the transformation of fluence maps into realizable sequences, leading to modified radiation doses that do not accurately target the target region while minimizing dose to surrounding areas.
Innovation Solution
A device and method utilizing a layered graph structure to determine illumination distributions by optimizing a cost function based on weights and regularization values, ensuring that the determined distributions closely match the intended fluence map and are realizable by the radiation device, thereby improving the quality of IMRT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluence maps are transformed into sequences of illumination distributions realizable by radiation device, then the illumination distributions become realizable by the radiation device, but the radiation doses are modified and the quality of IMRT is reduced
Solution Approach 1:
The patent applies preliminary action by incorporating realizability constraints directly into the fluence map calculation process itself, rather than performing a separate transformation step afterward. The system calculates fluence maps that are inherently realizable by the radiation device, considering device-specific constraints (such as multileaf collimator configurations) during the optimization process. This eliminates the need for post-processing transformation that would otherwise modify the radiation doses and reduce IMRT quality.
2Device complexity
If conventional two-step method is used to determine illumination distributions, then the calculation process is simplified, but the quality of IMRT is reduced due to dose modifications
Solution Approach 1:
The patent merges the fluence map calculation and the illumination distribution determination into a single integrated optimization process. Instead of performing separate transformation steps, the system simultaneously optimizes both the fluence maps and the corresponding realizable illumination distributions, ensuring that the device constraints are satisfied while maintaining IMRT quality. This unified approach preserves treatment quality while still providing a systematic calculation process.
Data Source
AI summary
The invention relates to a device for determining illumination distributions (18) for IMRT. A layered graph structure is used, which considers which extensions of an illumination distribution along a respective line and thus which illumination distributions are realizable, for determining extensions for the illumination distributions. Moreover, second weights defining fluences of the illumination distributions are determined such that a deviation between a provided fluence map and a fluence map formed by a combination of illumination distributions, which are defined by the respective determined extensions and the respective second weight, is minimized. This determination procedure leads to illumination distributions, which very well correspond to the provided fluence map and which are automatically realizable by the radiation device. This leads to an improved IMRT, wherein a post-processing of the determined illumination distributions for ensuring that the determined illumination distributions are really realizable is not necessarily required.