Intravoxel incoherent motion diffusion-weighted imaging of multiple myeloma lesions: Correlation with whole-body dynamic contrast agent-enhanced MR imaging¹

Purpose: To correlate intravoxel incoherent motion (IVIM) diffusionweighted imaging (DWI) parameters with the enhancement patterns of bone marrow and focal lesion obtained on wholebody (WB) dynamic contrast agent-enhanced (DCE) magnetic resonance (MR) images in patients with stage-III multiple myeloma (MM) before and after systemic therapy. Materials and Methods: Twenty-seven patients with MM were retrospectively included in this institutional review board-approved study. Requirement for written informed consent was waived. All patients underwent WB DCE MR imaging before treatment and 18 patients underwent repeat MR imaging 3 months after treatment. A transverse IVIM DWI sequence with 10 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, and 800 sec/mm2) was acquired within bone marrow and focal lesions. The IVIM parameters (perfusion fraction [f], molecular diffusion coefficient [D], and perfusion-related D [D∗]) and apparent diffusion coefficient (ADC) were extracted for both focal lesions and bone marrow and correlated with focal lesions and maximal bone marrow enhancement (BMEmax) (Spearman correlation coefficient) at baseline and at follow-up (Wilcoxon signed-rank test). Results: D and ADC values positively correlated with BMEmax (r = 0.7, P , .001; and r = 0.455, P = .0435, respectively). Patients with increased BMEmax showed significantly increased ADC and D within bone marrow versus patients who did not have increased BMEmax (ADC, 0.67 3 1023 mm2/sec vs 0.54 3 1023 mm2/sec, P = .03; D, 0.58 3 1023 mm2/sec vs 0.42 3 1023 mm2/sec, P , .001). Within focal lesions, f was the maximum in lesions that showed enhancement followed by washout. After treatment in good responders, the significant decrease in maximal enhancement value of focal lesions (baseline vs after treatment, 213.9% 6 78.7 [standard deviation] vs 131% 6 53.6, respectively; P , .001) was accompanied by a significant decrease in f (baseline vs after treatment, 11% 6 3.8 vs 5.8% 6 4.7, respectively; P , .001). Conclusion: Diffuse bone marrow involvement is associated with increased D. Hypervascular focal lesions with high maximal enhancement value of focal lesions also show high f value. Likewise, the decreased maximal enhancement value of focal lesions after treatment is accompanied by decreased f.