ESTRO 2023 - Abstract Book

S1449

Digital Posters

ESTRO 2023

Conclusion An automatic method for patient QA was implemented and evaluated for > 200 fractions on the MR-Linac. The patient QA was able to evaluate 99% of the fractions and reported that 90.2% of all fractions were delivered according to plan. The logfile analysis was incomplete in 6% of all plans due to treatment interruption.

PO-1731 Evaluation of materials suitable for anthropomorphic multimodality (CT/MRI) phantoms for RT purposes

M. Alzahrani 1 , D. Broadbent 2 , I. Teh 1 , B. Al-Qaisieh 2 , A. Walker 3 , R. Lamb 3 , R. Speight 2

1 University of Leeds, Department of Biomedical Imagining Science, Leeds, United Kingdom; 2 Leeds Teaching Hospitals NHS Trust, Department of Medical Physics and Engineering, Leeds, United Kingdom; 3 Leeds Test Objects Ltd., Leeds Test Objects Ltd., York, United Kingdom Purpose or Objective With the increasing use of magnetic resonance imaging (MRI) in radiotherapy (RT), there is a need for anthropomorphic multimodality phantoms to be used for various tasks including end-to-end tests of MRI-guided RT workflows. This project aims to find materials that mimic human tissue for MRI and computed tomography (CT) imaging and assess their stability over time and after radiation exposure. Materials and Methods Samples of the materials listed in Table 1 were produced according to the manufacturer's instructions and placed in a test tube. To measure stability over time, the CT number and T1 and T2 relaxation times of the samples have been measured monthly over 7 months. CT scans were acquired using Philips Brilliance BigBore (Philips Medical Systems, Best, Netherlands) with the following settings: 120 kVp, 104 mAs, 2 mm slice thickness, and in-plane resolution of 1.17 mm. MRI relaxation times were measured using a 3T Siemens Prisma MRI scanner (Siemens Healthineers, Erlangen, Germany). Inversion recovery and Spin-Echo-Multi-Contrast sequences were used to create T1 and T2 maps, respectively. On CT images, T1 and T2 maps, volumes within the materials were drawn, and the mean and standard deviation were measured within these volumes. To measure stability after radiation exposure, other samples of the same materials were exposed to radiation using an Elekta Versa HD linear accelerator, delivering 10, 100, 250, 500, and 1000 Gy. CT number and MRI relaxation times after radiation exposure were measured.