PET/MR for evaluation of musculoskeletal malignancies

To review the existing literature on PET/MR for musculoskeletal malignancies. PubMed (MEDLINE) was searched through July 2021. The search strategy focused on the keywords “PET/CT”, “PET/MR”, “MRI”, “attenuation correction”, “sarcoma”, “skeletal”, “metastases”, “myeloma”, “FDG”, “Sodium fluoride”, “PSMA”, “DOTATATE”, “fluciclovine”, and “FAPI”. 97 relevant papers were considered for review. Studies selected were primarily retrospective and prospective cohort studies. There is limited literature comparing PET/CT to PET/MR for evaluation of primary musculoskeletal malignancies and musculoskeletal metastatic disease. Most studies involve relatively small numbers of patients. Despite limited evidence and the lack of widespread application, PET/MR is a promising imaging technique for evaluating musculoskeletal malignancies. This is owing primarily to the strength of its constituent modalities. PET permits for acquisition of metabolic information using a variety of emerging novel radiopharmaceuticals. MR allows for assessment of bone marrow and for identification and characterization of soft-tissue lesions. Selection of appropriate radiopharmaceutical and MR protocol parameters is key for optimal evaluation. Although PET/MR has shown promise in evaluation of musculoskeletal involvement of multiple malignancies, it has not yet demonstrated broad superior to PET/CT. More research is needed to understand its value in the care of patients with such diseases.