ESTRO 2024 - Abstract Book

S4715

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

ESTR0 2024

References:

1. Visser S, O. Ribeiro C, Dieters M, et al. Robustness assessment of clinical adaptive proton and photon radiotherapy for oesophageal cancer in the model-based approach. Radiotherapy and Oncology. 2022;177:197-204. doi:10.1016/j.radonc.2022.11.001 2. Korevaar EW, Habraken SJM, Scandurra D, et al. Practical robustness evaluation in radiotherapy – A photon and proton-proof alternative to PTV-based plan evaluation. Radiotherapy and Oncology. 2019;141:267-274. doi:10.1016/j.radonc.2019.08.005

2840

Digital Poster

Dosimetric evaluation of MRI-based synthetic CT for head and neck photon and proton therapy

Marte Kåstad Høiskar 1 , Natalie Hornik 1,2 , Mirjam Delange Alsaker 3 , Kajsa Fridstrøm 1,3 , René M Winter 1 , Sigrun Saur Almberg 3 , Kathrine Røe Redalen 1 1 Norwegian University of Science and Technology, Department of Physics, Trondheim, Norway. 2 Eberhard Karls University Tübingen, Department of Radiation Oncologygen, Tübingen, Germany. 3 St. Olavs hospital, Cancer Clinic, Trondheim, Norway

Purpose/Objective:

Currently, computed tomography (CT) is the primary image modality for photon and proton dose calculations in radiotherapy (RT) planning. However, magnetic resonance imaging (MRI) has excellent soft tissue contrast better suited for delineation of targets and organs at risk (OAR), and its use in treatment planning is therefore increasing. It is feasible to use MRI-based synthetic CT (sCT) instead of conventional planning CT (pCT) for dose calculation in HNC photon therapy [1]. With sCT, an MRI-only workflow is possible which could reduce imaging costs, patient time and patient dose from CT, increase clinical efficiency and remove CT-MRI registration errors. Recognizing the increasing use of proton therapy for HNC, the dosimetric accuracy of sCT also needs to be estimated for proton therapy if MRI only workflow is to be used. Our main objectives were to investigate the feasibility of using MRI-derived sCT for proton planning and compare the results to sCT-based photon planning for HNC.

Material/Methods:

MRI and pCT in RT positioning were acquired for 13 HNC patients before they were treated with photon therapy. Photon and proton plans, prescribing 68 Gy (34 fractions of 2 Gy) to the clinical target volume (CTV), were created in RayStation 12A (RaySearch Laboratories AB, Sweden) based on the pCTs. Photon plans were made for all patients, as these were the clinical plans, while proton plans have so far been made for five of the patients.