18F-Fluorodeoxyglucose Positron Emission Tomography/Magnetic Resonance in Lymphoma: Comparison With 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography and With the Addition of Magnetic Resonance Diffusion-Weighted Imaging

OBJECTIVES: The aim of this study was to compare (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance (MR) (with and without diffusion-weighted imaging [DWI]) to (18)F-FDG PET/computed tomography (CT), with regard to the assessment of nodal and extranodal involvement, in patients with Hodgkin lymphoma and non-Hodgkin lymphoma, without restriction to FDG-avid subytpes. MATERIALS AND METHODS: Patients with histologically proven lymphoma were enrolled in this prospective, institutional review board–approved study. After a single (18)F-FDG injection, patients consecutively underwent (18)F-FDG PET⁄CT and (18)F-FDG PET/MR on the same day for staging or restaging. Three sets of images were analyzed separately: (18)F-FDG PET/CT, (18)F-FDG PET/MR without DWI, and (18)F-FDG PET/MR with DWI. Region-based agreement and examination-based sensitivity and specificity were calculated for (18)F-FDG PET/CT, (18)F-FDG PET/MR without DWI, and (18)F-FDG PET/MR DWI. Maximum and mean standardized uptake values (SUV(max), SUV(mean)) on (18)F-FDG PET/CT and (18)F-FDG PET/MR were compared and correlated with minimum and mean apparent diffusion coefficients (ADC(min), ADC(mean)). RESULTS: Thirty-four patients with a total of 40 examinations were included. Examination-based sensitivities for (18)F-FDG PET/CT, (18)F-FDG PET/MR, and (18)F-FDG PET/MR DWI were 82.1%, 85.7%, and 100%, respectively; specificities were 100% for all 3 techniques; and accuracies were 87.5%, 90%, and 100%, respectively. (18)F-FDG PET/CT was false negative in 5 of 40 examinations (all with mucosa-associated lymphoid tissue lymphoma), and (18)F-FDG PET/MR (without DWI) was false negative in 4 of 40 examinations. Region-based percentages of agreement were 99% (κ, 0.95) between (18)F-FDG PET/MR DWI and (18)F-FDG PET/CT, 99.2% (κ, 0.96) between (18)F-FDG PET/MR and (18)F-FDG PET/CT, and 99.4% (κ, 0.97) between (18)F-FDG PET/MR DWI and (18)F-FDG PET/MR. There was a strong correlation between (18)F-FDG PET/CT and (18)F-FDG PET/MR for SUV(max) (r = 0.83) and SUV(mean) (r = 0.81) but no significant correlation between ADC(min) and SUV(max) ((18)F-FDG PET/CT: r = 0.46, P = 0.65; (18)F-FDG PET/MR: r = 0.64, P = 0.53) or between ADC(mean) and SUV(mean) (respectively, r = −0.14, P = 0.17 for the correlation with PET/CT and r = −0.14, P = 0.14 for the correlation with PET/MR). CONCLUSIONS: (18)F-FDG PET/MR and (18)F-FDG PET/CT show a similar diagnostic performance in lymphoma patients. However, if DWI is included in the (18)F-FDG PET/MR protocol, results surpass those of (18)F-FDG PET/CT because of the higher sensitivity of DWI for mucosa-associated lymphoid tissue lymphomas.