Fully integrated 3D high-resolution multicontrast abdominal PET-MR with high scan efficiency

PurposeTo provide 3D multicontrast anatomical MR with high isotropic resolution and metabolic positron emission tomography (PET) images using a respiratory motion-compensated simultaneous PET-MR examination with high scan efficiency. Theory and MethodsStandard abdominal PET-MR examinations combine MR data obtained during multiple breath-holds with free-breathing PET acquisitions, limiting the achievable image resolution and potentially causing misalignment errors between breath-hold and free-breathing data. Here, a 3D free-breathing PET-MR acquisition is presented, yielding T-1 and T-2-weighted MR images with an isotropic resolution of 1.5mm(3). In addition, nonrigid respiratory motion information and respiratory-resolved attenuation-correction maps are obtained without an increase in scan time. Motion information is used in motion-compensated image reconstructions to improve MR and PET image quality while shortening scan times. ResultsThe proposed approach was evaluated in 11 oncology patients and provided respiratory motion information with an accuracy of 1.30.1mm. Sharpness of anatomical features was increased by 19 +/- 13% compared with the uncorrected MR images in a 54 +/- 26% shorter scan time than a gated MR acquisition. The MR-based motion information improved uptake values (75 +/- 94%) and resolution (16 +/- 27%) of simultaneously acquired PET images. ConclusionsThe proposed method provides motion-compensated 3D high-quality MR and PET images in a comprehensive and highly efficient examination. Magn Reson Med 79:900-911, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.