Interpolable Spot Placement Refinement for Radiation Dose Optimization
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Solution Overview
Problem
Existing radiation treatment planning systems for spot scanning struggle with optimizing spot placements that conform to the target volume while minimizing exposure to healthy tissue, achieving uniform dose distribution, and reducing treatment time, as varying spot positions during optimization complicates the process.
Innovation Solution
A method involving normalization of spot dose distributions and recursive refinement of spot arrangements in a hierarchical data structure, such as an octree, to ensure similarity criteria are met, allowing for efficient interpolation and optimization of spot placements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spot positions are fixed in a predetermined pattern for each energy layer, then the treatment planning process is simpler and faster, but the ability to achieve sharp penumbra and uniform dose distribution is limited
Solution Approach 1:
The target volume is divided into multiple energy layers, with spot patterns generated independently for each layer. This segmentation allows the system to maintain computational efficiency while achieving precise dose distribution through layered optimization
Solution Approach 2:
Different spot spacing and patterns are applied to different regions within each energy layer based on local dose requirements. Heterogeneous regions receive finer spot spacing while homogeneous regions use coarser spacing, optimizing both precision and computational efficiency locally
2Manufacturing precision
If spot spacing is reduced to improve dose uniformity and penumbra, then dose distribution quality improves, but treatment time increases due to more spots
Solution Approach 1:
Spot spacing is optimized locally rather than uniformly across the entire target volume. Regions requiring higher precision (heterogeneous areas, edges) use finer spot spacing, while homogeneous central regions use coarser spacing, reducing total spot count while maintaining dose uniformity
Solution Approach 2:
The system applies fine spot spacing only where necessary to achieve dose uniformity and sharp penumbra, rather than uniformly across all regions. This partial application of fine spacing reduces treatment time while maintaining critical dose distribution quality
3Manufacturing precision
If spot patterns are optimized for each energy layer independently, then lateral penumbra and dose conformity improve, but computational complexity increases
Solution Approach 1:
The optimization problem is segmented into independent sub-problems for each energy layer. This allows parallel processing and reduces computational complexity while maintaining the ability to achieve sharp penumbra through layer-specific optimization
Solution Approach 2:
Spot patterns are pre-calculated and stored for each energy layer before treatment delivery. This preliminary optimization reduces computational complexity during actual treatment while maintaining precise dose conformity through pre-planned spot arrangements
Data Source
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Figure 5
AI summary
An initial, relatively coarse arrangement (500) of spots (501-505; 521-525) in a target volume (510) and a respective dose distribution per spot are accessed from memory or determined. If the dose distributions of neighboring spots do not satisfy a similarity criterion, then a new set of spots with finer spacing is determined for the regions that include dissimilar spots (e.g., spots are added between the dissimilar spots), and spot dose distributions are determined for the new spot arrangement (600). The process is repeated until the similarity criterion is satisfied for all or a threshold number of spots or until a minimum spot spacing is reached. The final arrangement (700) of spots (751-754) and dose distributions for the spots can be stored. During subsequent optimization of a treatment plan based on the final arrangement of spots, a dose distribution for a point that is between the spots can be determined by interpolating the dose distributions of nearby spots.