Integrated whole-body PET/MRI with 18F-FDG, 18F-FDOPA, and 18F-FDA in paragangliomas in comparison with PET/CT: NIH first clinical experience with a single-injection, dual-modality imaging protocol

PURPOSE: Paragangliomas (PGLs) are tumors that can metastasize and recur; therefore, lifelong imaging follow-up is required. Hybrid PET/CT is an essential tool to image PGLs. Novel hybrid PET/MRI scanners are currently being studied in clinical oncology. We studied the feasibility of simultaneous whole-body PET/MRI to evaluate patients with PGLs. METHODS: Fifty-three PGLs or PGL-related lesions from 8 patients were evaluated. All patients underwent a single-injection, dual-modality imaging protocol consisting of a PET/CT and a subsequent PET/MRI scan. Four patients were evaluated with ¹⁸F-FDG, 2 with F-fluorodihydroxyphenylalanine, and 2 with ¹⁸F-fluorodopamine. PET/MRI data were acquired using a hybrid whole-body 3-tesla integrated PET/MRI scanner. PET and MRI data (Dixon sequence for attenuation correction and T2-weighted sequences for anatomic allocation) were acquired simultaneously. Imaging workflow and imaging times were documented. PET/MRI and PET/CT data were visually assessed (blindly) in regards to image quality, lesion detection, and anatomic allocation and delineation of the PET findings. RESULTS: With hybrid PET/MRI, we obtained high-quality images in an acceptable acquisition time (median, 31 minutes; range, 25-40 minutes) with good patient compliance. A total of 53 lesions, located in the head and neck area (6 lesions), mediastinum (2 lesions), abdomen and pelvis (13 lesions), lungs (2 lesions), liver (4 lesions), and bones (26 lesions), were evaluated. Fifty-one lesions were detected with PET/MRI and confirmed by PET/CT. Two bone lesions (L4 body, 8 mm, and sacrum, 6 mm) were not detectable on an ¹⁸F-FDA scan PET/MRI, likely because ¹⁸F-FDA was washed out between PET/CT and PET/MRI acquisitions. Coregistered MRI tended to be superior to coregistered CT for head and neck, abdomen, pelvis, and liver lesions for anatomic allocation and delineation. CONCLUSIONS: Clinical PGL evaluation with hybrid PET/MRI is feasible with high-quality image and can be obtained in a reasonable time. It could be particularly beneficial for the pediatric population and for precise lesion definition in the head and neck, abdomen, pelvis, and liver.