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An Adaptive Planning Strategy for Station Parameter Optimized Radiation Therapy (SPORT): Segmentally Boosted VMAT

R Li

R Li*, L Xing, Stanford Univ School of Medicine, Stanford, CA

TH-A-137-2 Thursday 8:00AM - 9:55AM Room: 137

Purpose: The concept of station parameter optimized radiation therapy (SPORT) was recently introduced to maximally utilize the technical capacity of a digital LINAC. Here we present a rotational arc implementation of SPORT in which the traditional 1-arc VMAT is differentially boosted to improve target coverage while sparing critical structures.

Methods: The demand for intensity modulation varies from angle to angle. The essence of the new treatment scheme is to provide the necessary beam intensity modulation in those directions that need it. We utilize a demand metric based on a modulation index at each station point to decide which station or control points need intensity modulation. To boost the modulation at selected stations, additional segments are added in the vicinity of the selected stations. The added segments are then optimized together with the original set of station control points as a whole. We apply the segmentally boosted planning technique to four previously treated clinical cases: two head and neck (HN) cases, one prostate case, and one liver case.

Results: The proposed segmentally boosted VMAT technique achieves better dose distributions than 1-arc VMAT in all four clinical cases. Compared with 2-arc VMAT, segmentally boosted VMAT achieves similar critical structure sparing for the liver and prostate case, and outperforms 2-arc VMAT in the more complicated HN cases. Yet, segmentally boosted VMAT achieves such plan quality generally with fewer machine monitor units than 2-arc VMAT by up to 30%, which leads to less leakage/scatter dose to the patient and can potentially translate into faster dose delivery.

Conclusion: We have proposed a rotational arc strategy to optimally implement SPORT. The resultant dose distribution is improved as compared with the 1- and 2-arc VMAT for clinically complicated cases. The delivery can still be accomplished by a single arc, leading to a simplified and efficient delivery process.

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