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

PURPOSE: To 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 METHODS: Standard 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 T1 and T2 -weighted MR images with an isotropic resolution of 1.5 mm3 . 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.

RESULTS: The proposed approach was evaluated in 11 oncology patients and provided respiratory motion information with an accuracy of 1.3 ± 0.1 mm. 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.

CONCLUSIONS: The 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. © 2017 International Society for Magnetic Resonance in Medicine.