Diagnostic performance of fluorine-18-fluorodeoxyglucose PET/MRI for detection of disease recurrence in differentiated thyroid cancer: a compartment-based analysis.

[OBJECTIVES] The objective of this study is to evaluate the diagnostic performance of neck fluorodeoxyglucose (FDG) PET/MRI in addition to whole-body PET/computed tomography (CT) and to compare it with MRI in the detection of suspicion of disease relapse in patients with differentiated thyroid cancer (DTC) who underwent total thyroidectomy and radioactive iodine therapy.

[METHODS] Twenty-nine patients with DTC who underwent whole-body 18 F-FDG PET/CT followed by neck PET/MRI because of increased serum thyroglobulin (Tg) or anti-Tg antibody levels and negative 131 I whole-body scan were included. At least 6 months of clinical and radiological (neck ultrasound) follow-up or histopathological examination results were accepted as the gold standard. Lesion and compartment-based analyses were performed to evaluate the diagnostic performances of PET/CT, MRI, and PET/MRI. In addition, changes of clinical management were evaluated.

[RESULTS] On lesion-based analysis, for PET/CT, MRI, and PET/MRI: sensitivity: 33.3, 33.3, and 37%; specificity: 90.1, 87.9, and 95.9%; accuracy: 87.5, 85.4, and 93.2 were calculated, respectively. Specificity of PET/MRI was significantly superior to PET/CT and MRI ( P  of0.001); however, sensitivity of PET/MRI was not significant to PET/CT and MRI ( P  of0.05). On compartment-based analysis, specificity of PET/MRI and MRI were comparable but significantly superior to PET/CT at levels 1 and 2; however, specificity of PET/CT and PET/MRI were comparable but significantly superior than MRI, especially at levels 3, 4, and 5.

[CONCLUSION] PET/MRI especially helps in the accurate exclusion of findings that are suspicious on PET/CT and MRI, and has the potential to change the clinical management by identifying uncertain neck findings.