18F-FDG-PET/MR increases diagnostic confidence in detection of bone metastases compared with 18F-FDG-PET/CT.

PURPOSE The aim of this study was to compare detection, lesion conspicuity and reader confidence of F-fluorodeoxyglucose (F-FDG)-PET/MR and F-FDG-PET/computed tomography (CT) in patients with F-FDG avid bone metastases. MATERIALS AND METHODS In this prospective study, a total of 30 PET/CT and PET/MRI data sets were performed in 24 patients. Each examination was evaluated for the presence of PET-positive bone lesions consistent with metastatic involvement. Conspicuity of PET-positive bone lesions was evaluated on the corresponding PET/CT and PET/MR images and compared using the Wilcoxon signed-ranks test. Reader confidence was determined to evaluate whether PET/CT or PET/MR was more useful for the assessment of the bone metastases and was compared using Student's t-test. RESULTS Overall, in both examinations, PET/CT and PET/MRI detected 86 F-FDG-positive bone lesions. On all 30 PET/MRI examinations, at least one morphological correlate for F-FDG-positive bone lesions was found on the MR component (82 out of 86 lesions). PET/CT imaging allowed identification of corresponding structural changes on the CT component in 23 out of 30 studies (65 out of 86 lesions). In lesion-by-lesion analysis, the mean lesion conspicuity was significantly better on T1 fat MR imaging compared with CT imaging (P=0.005). In seven out of 30 studies, a significant increase in reader confidence of PET/MRI compared with PET/CT was found. CONCLUSION PET/MRI offers higher reader confidence and improved conspicuity in bone metastases compared with PET/CT. However, the overall detection rate was not different. The highest possible clinical impact of PET/MRI appears to be in patients with limited, early bone metastatic disease.