The diagnostic value of SE MRI and DWI of the spine in patients with monoclonal gammopathy of undetermined significance, smouldering myeloma and multiple myeloma.

OBJECTIVES: To evaluate DWI of the bone marrow in the differentiation of monoclonal gammopathy of undetermined significance (MGUS), smouldering myeloma (SMM) and multiple myeloma (MM). METHODS: The retrospective study includes 64 patients with MGUS, 27 with SMM, 64 with new MM and 12 controls. Signal intensity (SI) of spinal SE-MRI and DWI (b0-1000) as well as apparent diffusion coefficients (ADC) were measured in the T10 and L3. Qualitative assessment of b-images was performed by one experienced radiologist. RESULTS: ADC600 and ADC1000 are the best ADC values in differentiating patient groups (p < 0.030). SIT2, SIb1000 and ADC1000 are higher and SIT1 lower in L3 compared to T10 (p < 0.050). All quantitative parameters of L3 can differentiate significantly between MGUS and MM (p < 0.050) and between patients with percentage plasma cells (PC%) between 0-10 % compared to >50 % (p = 0.001). Only SIT2 for L3 can differentiate MGUS from SMM (p = 0.044) and PC%0-10 from PC%10-25 (p = 0.033). Qualitative interpretation of b1000 images allows differentiating MM patients from those with MGUS or SMM (p < 0.001). CONCLUSIONS: Spinal SE-MRI can differentiate among MGUS, SMM, MM and control subjects. DWI based on the SI on b1000 images and ADC values is increased in MM compared to MGUS and SMM. Qualitative assessment of b-images can differentiate MM from MGUS or SMM. KEY POINTS: • ADC values are higher in patients with MM compared to MGUS • DWI parameters change late in disease evolution • DWI is sensitive but not specific in diagnosing patients with MM • Qualitative DWI assessment is good in detecting myeloma patients.