ESTRO 2021 Abstract Book

S321

ESTRO 2021

Proffered papers: Proffered papers 27: Large-scale assurance of quality

OC-0423 Developing quality assurance tests for simultaneous PET-MR imaging for radiotherapy planning J. Wyatt 1,2 , E. Howell 3 , H. McCallum 3,4 , R. Maxwell 3 1 Newcastle University, Translational and Clinical Research Institute, Newcastle upon Tyne, United Kingdom; 2 Newcastle upon Tyne Hospitals NHS Foundation Trust, Northern Centre for Cancer Care, Newcastle upon Tyne, United Kingdom; 3 Newcastle University, Translation and Clinical Research Institute, Newcastle upon Tyne, United Kingdom; 4 Newcastle upon Tyne Hospitals NHS Foundation Trust, Northern Centre for Cancer care, Newcastle upon Tyne , United Kingdom Purpose or Objective Simultaneous Positron Emission Tomography – Magnetic Resonance (PET-MR) imaging enables acquiring MR anatomical and functional information and PET molecular information with high degrees of spatial alignment. This has great potential to improve radiotherapy by identifying tumour sub-volumes to receive ‘boost’ radiation doses, potentially increasing tumour control. To use PET-MR imaging for radiotherapy planning requires a comprehensive Quality Assurance (QA) programme to be developed, tailored to radiotherapy purposes. This study aimed to develop the tests needed for such a programme and assess their repeatability and longitudinal stability on a single PET-MR scanner. Materials and Methods The QA tests developed were: 1) electromechanical accuracy, 2) MR image quality, 3) MR geometric distortion, 4) PET-MR alignment accuracy, 5) PET Standard Uptake Value (SUV) accuracy and 6) diffusion weighted (DW)-MR Apparent Diffusion Coefficient (ADC) accuracy. Each test used a dedicated phantom: 1) Aquarius MRI phantom (LAP GmbH, Schwarzenbruck, Germany), 2) American College of Radiologists large image quality phantom, 3) GRADE phantom (Spectronic Medical, Helsingborg, Sweden), 4) VQC phantom (GE Healthcare, Milwaukee, USA), 5) in-house uniform PET activity phantom and 6) in-house phantom with vials containing n-nonane, n-undecane and tridecane, immersed in water. Each test was analysed automatically or semi-automatically, using in-house developed software. The repeatability of each test was evaluated by acquiring three separate measurements with independent phantom positions on the same day. The longitudinal stability was assessed through making monthly measurements over 6 months. All measurements were carried out on a Signa 3T PET-MR scanner (version MP26, GE Healthcare). Results The repeatability and stability of the MR geometric distortion tests appeared high, with the distribution of distortions within different distances from the isocentre being similar between repeats and over time (figure