Quantitative Diffusion-weighted Imaging of the Bone Marrow: An Adjunct Tool for the Diagnosis of a Diffuse MR Imaging Pattern in Patients with Multiple Myeloma

Purpose: To evaluate the apparent diffusion coefficients (ADCs) of magnetic resonance (MR) imaging patterns in the bone marrow of patients with multiple myeloma (MM) and to determine a threshold ADC that may help distinguish a diffuse from a normal pattern with high accuracy. Materials and Methods: This prospective study was approved by the ethics review board, and informed consent was obtained. Ninety-nine patients with newly diagnosed, untreated MM and 16 healthy control subjects underwent spinal MR imaging including diffusion-weighted imaging, and bone marrow ADCs were calculated. Pattern assignment was based on visual assessment of conventional MR images. The Kruskal-Wallis H test, the Mann-Whitney test, and the oneway analysis of variance were used to compare ADCs between patient subsets and control subjects, and a receiver operating characteristic analysis was performed. Results: Mean ADCs 6 standard deviation in patients with MM for the normal, focal, and diffuse MR imaging patterns were 0.360 x 10(-3) mm(2)/sec +/- 0.110, 1.046 x 10(-3) mm(2)/sec +/- 0.232, and 0.770 x 10(-3) mm(2)/sec +/- 0.135, respectively. There were significant differences in ADCs between diffuse and normal (P< .001), diffuse and focal (P< .001), and focal and normal (P< .001) patterns. Patients with a diffuse pattern had more features of advanced disease, higher international staging system score, increased incidence of high-risk cytogenetics, and higher revised international staging system score. ADCs greater than 0.548 x 10(-3) mm(2)/sec showed 100% sensitivity (26 of 26) and 98% specificity (48 of 49) for the diagnosis of a diffuse (vs normal) MR imaging pattern, whereas an ADC greater than 0.597 x 10(-3) mm(2)/sec showed 96% sensitivity (25 of 26) and 100% specificity (49 of 49). Conclusion: ADCs of MR imaging patterns in patients with MM differ significantly. A diffuse MR imaging pattern can be distinguished more objectively from a normal MR imaging pattern by adding quantitative diffusion-weighted imaging to standard MR imaging protocols. (C) RSNA, 2016