Clinically Valuable Quality Control for PET/MRI Systems: Consensus Recommendation From the HYBRID Consortium

Alejandra Valladares,Paul Marsden,Francesco Padormo,Ronald Peeters,Laura Daltoso,Ivo Rausch,Zacharias Chalampalakis,Sebastian Poth,Thomas Beyer,Michel Koole,Claude Comtat,Esteban Solari,Adam E Hansen,Sahar Ahangari,Ronald Boellaard,Johan Nuyts,Jane Mackewn

doi:10.3389/fphy.2019.00136

Abstract

Quality control (QC) of medical imaging devices is essential to ensure their proper function and to gain accurate and quantitative results. Therefore, several international bodies have published QC guidelines and recommendations for a wide range of imaging modalities to ensure adequate performance of the systems. Hybrid imaging systems such as positron emission tomography / computed tomography (PET/CT) or PET/ magnetic resonance imaging (PET/MRI), in particular, present additional challenges caused by differences between the combined modalities. However, despite the increasing use of this hybrid imaging modality in recent years, there are no dedicated QC recommendations for PET/MRI. Therefore, this work aims at collecting information on QC procedures across a European PET/MRI network, presenting quality assurance procedures implemented by PET/MRI vendors and achieving a consensus on PET/MRI QC procedures across imaging centers. Users of PET/MRI systems at partner sites involved in the HYBRID consortium were surveyed about local frequencies of QC procedures for PET/MRI. Although all sites indicated that they perform vendor-specific daily QC procedures, significant variations across the centers were observed for other QC tests and testing frequencies. Likewise, variations in available recommendations and guidelines and the QC procedures implemented by vendors were found. Based on the available information and our clinical expertise within this consortium, we were able to propose a minimum set of PET/MRI QC recommendations including the daily QC, cross-calibration tests and an image quality (IQ) assessment for PET and coil checks and MR image quality tests for MRI. Together with regular checks of the PET–MRI alignment, proper PET/MRI performance can be ensured.

Highlights

With the introduction of clinical PET/MRI systems in 2010 [1, 2], a novel hybrid PET system became available, in addition to PET/CT and SPECT/CT
All of the eight participating centers completed the form for the available PET/MRI systems on-site resulting in reported QC procedures for five Siemens Biograph mMR PET/MR, two GE SIGNA PET/MR, and one Philips Ingenuity TF PET/MR
Survey forms were mainly completed by the on-site medical physics expert

Summary

Introduction

With the introduction of clinical PET/MRI systems in 2010 [1, 2], a novel hybrid PET system became available, in addition to PET/CT and SPECT/CT. The combination of PET with MRI has several advantages; it offers high soft tissue contrast by MRI, together with a reduced radiation burden compared to CT [3]. The high-resolution anatomical images from MRI can be used for accurate partial volume correction (PVC) [4] and fast MRI sequences can be used to correct for motion in PET examinations [5]. A broad spectrum of available MRI sequences offers a variety of multi-parametric information, which bears high potential to improve disease characterization through radiomics and machine learning (ML) approaches [6]. The typically rather low number of available datasets for a specific disease from PET/MRI in a single-center renders a systematic evaluation of possible advantages over other modalities, and the use of PET/MRI data for ML approaches challenging. Pooling of PET/MRI data across multiple imaging centers is desirable

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