Particle Therapy Spot Dose Control for Organ Motion
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Solution Overview
Problem
Existing particle therapy systems face challenges in delivering partial spot doses that are smaller than the minimum dose (Dmin) with sufficient accuracy, especially when organ motion occurs and the distribution of total spot doses is non-homogeneous, leading to potential errors in dose delivery.
Innovation Solution
The system determines the number of layer paintings (Nlayer_painting) and the number of times a spot is irradiated (Nspot_painting) such that each partial spot dose is equal to or greater than Dmin, allowing for flexible choice of Nlayer_painting and minimizing the effects of organ motion by adapting Nspot_painting based on the condition Dspot/Nlayer_painting >= Dmin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of layer paintings (Nlayer_painting) is increased to reduce organ motion effects, then dose uniformity improves, but partial spot doses may fall below the minimum deliverable dose (Dmin) for spots with low prescribed total dose
Solution Approach 1:
The system dynamically adjusts the number of spot paintings (Nspot_painting) for each individual spot based on its prescribed total dose and the minimum deliverable dose constraint. This dynamic adaptation allows different spots within the same layer to be painted different numbers of times, ensuring that low-dose spots receive fewer paintings while maintaining dose uniformity across the entire layer.
Solution Approach 2:
The patent applies local quality by treating each spot individually with customized painting parameters. Instead of uniformly distributing paintings across all spots, the system assigns specific Nspot_painting values to each spot based on its local dose requirements, ensuring that each spot receives an appropriate number of paintings that maintains both dose uniformity and delivers accurate partial doses.
2Ease of operation
If the partial spot dose is calculated by dividing total dose by number of layer paintings, then dose distribution is simplified, but the system cannot deliver doses below Dmin with sufficient accuracy
Solution Approach 1:
The system changes the parameter Nspot_painting from a fixed value (equal to Nlayer_painting for all spots) to a variable parameter that is optimized for each spot. This parameter change allows the partial spot dose to always be equal to or greater than Dmin while still achieving the prescribed total dose through multiple paintings, thereby maintaining measurement precision.
3Reliability
If spots with low prescribed total dose are irradiated multiple times to reduce organ motion effects, then dose uniformity improves, but treatment time increases due to excessive paintings
Solution Approach 1:
The system applies partial action by irradiating spots with fewer paintings than the maximum Nlayer_painting when their prescribed total dose is low. Instead of uniformly applying excessive paintings to all spots, the system applies only the necessary number of paintings (Nspot_painting) for each spot, reducing unnecessary treatment time while maintaining dose uniformity through optimized painting distribution.
Data Source
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AI summary
The present invention relates to a particle therapy system (10) that comprises a spot scanning system to irradiate with a particle beam (50) a plurality of spots in a layer (65) of a target (60) with prescribed spot doses for each spot of the layer. The therapy system is further adapted to perform multiple paintings of the layer (65) and to deliver partial spot doses to selected spots of the layer during each painting time so that each spot of the layer will have received its prescribed dose after completion of the multiple paintings. The therapy system further comprises means (45) for setting the partial spot doses and the number of times that a spot will be selected for irradiation in the course of the multiple paintings to such values that any spot of the layer will never have to be irradiated with a partial dose which would fall below a minimum dose deliverable by the system (10), and this whatever the number chosen for the number of layer paintings. The invention also relates to a corresponding irradiation method.