Developing quality assurance tests for simultaneous Positron Emission Tomography - Magnetic Resonance imaging for radiotherapy planning

Jonathan J Wyatt; Hazel M McCallum; Ross J Maxwell

doi:10.1016/j.phro.2022.03.003

Developing quality assurance tests for simultaneous Positron Emission Tomography - Magnetic Resonance imaging for radiotherapy planning

Phys Imaging Radiat Oncol. 2022 Apr 20:22:28-35. doi: 10.1016/j.phro.2022.03.003. eCollection 2022 Apr.

Authors

Jonathan J Wyatt^{1

2}, Hazel M McCallum^{1

2}, Ross J Maxwell¹

Affiliations

¹ Translational and Clinical Research Institute, Newcastle University, Newcastle, UK.
² Northern Centre for Cancer Care, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle, UK.

Abstract

Background and purpose Simultaneous Positron Emission Tomography - Magnetic Resonance (PET-MR) imaging can potentially improve radiotherapy by enabling more accurate tumour delineation and dose painting. The use of PET-MR imaging for radiotherapy planning requires a comprehensive Quality Assurance (QA) programme to be developed. This study aimed to develop the QA tests required and assess their repeatability and stability. Materials and methods QA tests were developed for: MR image quality, MR geometric accuracy, electromechanical accuracy, PET-MR alignment accuracy, Diffusion Weighted (DW)-MR Apparent Diffusion Coefficient (ADC) accuracy and PET Standard Uptake Value (SUV) accuracy. Each test used a dedicated phantom and was analysed automatically or semi-automatically, with in-house software. Repeatability was evaluated by three same-day measurements with independent phantom positions. Stability was assessed through 12 monthly measurements. Results The repeatability Standard Deviations (SDs) of distortion for the MR geometric accuracy test were $⩽ 0.7 mm$ . The repeatability SDs in ADC difference from reference were $⩽ 3 %$ for the DW-MR accuracy test. The PET SUV difference from reference repeatability SD was $0.3 %$ . The stability SDs agreed within $0.6 mm$ , 1 percentage point and 1.4 percentage points of the repeatability SDs for the geometric, ADC and SUV accuracy tests respectively. There were no monthly trends apparent. These results were representative of the other tests. Conclusions QA Tests for radiotherapy planning PET-MR have been developed. The tests appeared repeatable and stable over a 12-month period. The developed QA tests could form the basis of a QA programme that enables high-quality, robust PET-MR imaging for radiotherapy planning.

Keywords: Magnetic resonance imaging; PET-MR; Positron Emission Tomography; QA; Quality Assurance; Radiotherapy.