ESTRO 2024 - Abstract Book

S4816

Physics - Quality assurance and auditing

ESTRO 2024

Keywords: Proton Therapy, Commissioning, Gantry-Less

1492

Digital Poster

4D proton MC dose calculation before treatment: An independent free-breathing QA frame

Xuying Shang 1,2,3 , Yaoying Liu 1,4,3 , Zishen Wang 2 , Chunfeng Fang 2 , Nan Li 2 , Yue Zou 2 , Wei Zhao 1,5 , Xiaoyun Le 1 , Gaolong Zhang 1 , Shouping Xu 3,1 1 Beihang University, School of Physics, Beijing, China. 2 Hebei Yizhou Tumor Hospital, Department of Radiation Oncology, Hebei zhuozhou, China. 3 Chinese Academy of Medical Sciences and Peking Union Medical College, National Cancer Center/ National Clinical Research Center for Cancer/Cancer Hospital, Beijing, China. 4 PLA General Hospital, Department of Radiation Oncology, Beijing, China. 5 Yuhang Xixi Octagon City, Beihang Hangzhou Innovation Institute, Hangzhou, China

Purpose/Objective:

Current studies made 4D proton Monte Carlo (MC) dose calculations with log files after treatment, to achieve retrospective free-breathing quality assurance (QA). However, making 4D dose QA before treatment has more clinical reference values. Consequently, the study would present a 4D dose pre-review frame in proton therapy, with spots time predictions and an independent proton MC frame.

Material/Methods:

A spot-time prediction model was established by fitting functions between location, energy, weight of spots in RTPLANs and time of spots in log files. The model can predict the delivery time of all spots in an RTPLAN before treatment, and the spots can be distributed to different phases in 4DCT according to the predicted spots' time and breathing phase time. Subsequently, a commissioned independent proton MC frame can accurately calculate doses in phase CTs. Consequently, a parallel operation accelerated registration algorithm generates deformation vector fields (DVFs) between phase CTs and planning CT (pCT). The DVFs can align doses from phase CTs to pCT; adding aligned doses forms the free-breathing 4D dose (Figure 1). The study enrolled a 5-field pencil beam scanning lung case with a 10-phase free-breathing 4DCT. The clinical target volume (CTV) was 33 cc and the breathing cycle was 4.7s. The breathing amplitude was 0.8 mm in the left-right (LR) direction, 3.9 mm in the anterior-posterior (AP) direction, and 5.1 mm in the superior-inferior (SI) direction.