Rapid PET/MRI to Assess Multiple Myeloma Using T2-Weighted Imaging With Uniform Fat Suppression

18 F-fluorodeoxyglucose positron-emission tomography (FDG PET) and whole-body (WB) MRI with diffusion weighted imaging (DWI) are complementary in assessment of multiple myeloma. However, WB DWI suffers from prolonged acquisition times and artifacts. Alternatively, rapid T2-weighted MRI with 2-point Dixon fat-suppression (T2-FS) has demonstrated promise in detection of bone lesions in exam times shorter than DWI. This study evaluated (1) the accuracy of rapid WB T2-FS for multiple myeloma lesion detection and (2) the incremental impact of adding DWI and FDG PET to T2-FS on diagnostic accuracy and patient care management.

This retrospective single-center study included patients with clinical WB PET/MRI exams obtained for multiple myeloma. T2-FS, DWI, and PET were reviewed in consensus by 2 readers, each technique reviewed blinded to the other 2 and to other imaging/clinical information. Focal lesions and nonfocal bone marrow disease were recorded. Per-lesion sensitivity and per-patient sensitivity and specificity for each technique were compared with a composite reference standard using McNemar exact test; 95% confidence intervals were calculated, and P <0.05 was considered significant. The incremental impact of adding DWI and PET to T2-FS on diagnostic accuracy and patient care management was recorded.

From 34 PET/MRI exams from 34 patients, 3 incomplete exams were excluded. Among the 31 included exams, T2-FS demonstrated a significantly higher per-lesion sensitivity than DWI and PET, at 91.9%, 66.7%, and 44.4%, respectively ( P <0.001). T2-FS identified all 21 patients with disease, compared with 85.7% for both DWI and PET; this difference did not reach statistical significance ( P >0.050). Adding DWI to T2-FS did not change management in any patient; adding PET to T2-FS changed management in 3 patients.

T2-FS was more rapid and more sensitive than DWI for assessment of multiple myeloma. Unlike FDG PET, addition of DWI did not impact clinical management. Larger prospective studies for further validation are needed.