ESTRO 2024 - Abstract Book

S4647

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTR0 2024

1 Particle Therapy Research Center (PARTREC), Department of Radiation Oncology, Groningen, Netherlands. 2 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands. 3 RaySearch Laboratories AB, RaySearch Laboratories AB, Stockholm, Sweden

Purpose/Objective:

Positron emission tomography (PET), imaging positron emitters created by the proton beam, is being considered as a tool for treatment verification in proton therapy [1]. Attention is now focused on an in-beam PET application during treatment in order to detect shorter-lived isotopes, minimizing biological isotope washout, and avoiding patient repositioning errors. 12N, having a half-life of only 11 milliseconds, is a very promising positron emitter for this purpose [2, 3]. Considering the 12N advantages, the RIVER (Real Time in Vivo Verification of Proton Therapy) project focuses on the investigation of 12N imaging. Verification of proton therapy irradiation by means of PET is commonly based on the comparison of measured and predicted PET images. There is currently no established framework for comparing and validating PET measurements obtained through 12N imaging. We present the concept, design, and implementation of the new Monte Carlo framework. We are focusing on head and neck cancer, which typically involves numerous healthy organs in close proximity to the tumor. We aim to realistically mimic the full clinical workflow using clinical irradiations of an anthropomorphic head phantom. The first measurement used for validation of the calculational framework was performed using a 120 MeV spot proton beam, a CIRS 731-HN anthropomorphic head phantom, and a dual-panel Biograph Siemens mCT PET scanner. The second measurement was carried out at the proton therapy center using the same PET scanner and head phantom and a uniform 400 cGy dose delivery (minimum dose of 392 cGy and maximum dose of 408 cGy) to a 4 cm diameter spherical volume located in the brain and the neck region. The brain plan consisted of 987 spots with energies ranging from 102.7 MeV to 146.5 MeV. The experimental and simulation setups are presented in Fig. 1. For the simulation framework, the distribution of 12N and other longer-lived positron emitters created during the irradiation was calculated by a research version 11B-IonPG of the RayStation treatment planning system. This output, a CT image of the phantom, and the characteristics of our PET scanner were used as the input for GATE Monte Carlo simulations of PET imaging. Based on the RayStation output, we studied the 16O(p,3p3n)11C, 16O(p,pn)15O, 16O(p,a)13N, 12C(p,d)11C, and 12C(p,n)12N channels in Monte Carlo simulations. The reconstructed PET images were predicted by the newly designed RayStation/GATE Monte Carlo framework and compared with the images based on the experimental PET data. Material/Methods: