LAUSR

Multiple myeloma (MM), the second most common hematologic malignancy, is a plasma cell dyscrasia, characterized by a proliferation and accumulation of monoclonal plasma cells resulting in osteolytic lesions and fractures. Plasma cell fraction in the bone marrow is therefore critical for the classification and optimal clinical management of patients with plasma cell dyscrasias. Standard prognostic classifications used in newly diagnosed MM include the Durie–Salmon classification and International Staging System (ISS). Recent technological advances in the detection of plasma cell pathology include magnetic resonance imaging (MRI) of bone lesions, diffusion-weighted imaging, and the multiecho Dixon technique. The information about bone marrow infiltration as well as bone destruction provided by MRI allows assessing the disease activity. What is more, quantitative imaging techniques such as diffusion-weighted imaging (DWI) or dynamic contrast-enhanced (DCE) imaging can be used as an imaging biomarker for the assessment of prognosis and treatment response in MM. The feasibility of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) for grading or characterization of malignant tumors of solid organs has been demonstrated in several studies. DWI characterizes increased diffusivity caused by bone marrow infiltration of MM. Quantitative parameters derived from IVIM-DWI can separately reflect tissue diffusivity and tissue microcapillary perfusion. IVIM-DWI, which allows simultaneous quantification of both microperfusion and free water diffusion, can be an ideal technique in a situation when the use of DCE-MRI is limited due to compromise of renal function. The Dixon technique was developed to provide separate spin-echo images of fat and water and found its application in whole-body evaluation of MM patients. Fat–water imaging can detect fat and hematopoietic marrow alterations. The original two-point technique with one in-phase and one opposed-phase image was later extended to multipoint methods. Echo-based Dixon MRI has several advantages over conventional T1or T2-weighted imaging. In this issue of JMRI, Jo et al searched for ways of improving prognostic assessment in MM development. Their retrospective study aimed at evaluation of the efficiency and profitability of multiparametric MRI (including IVIM-DWI and multiecho Dixon) for predicting the clinical stages of initially diagnosed MM. The MRI analysis consisted of signal intensity measurements of the bone marrow in lumbar or thoracic spine by region of interest (ROI) in a series of 78 patients (mean age: 61.3 years) who were diagnosed with MM. All the patients were classified according to the ISS, with 38 patients as ISS stage I, 22 patients as ISS stage II, and 18 patients as ISS stage III. The ISS II and III groups were categorized as the advanced-stage group, whereas the ISS I group was considered the early-stage group. The apparent diffusion coefficient (ADC) derived from DWI can be used to measure the magnitude of hindered water diffusion in tissues. It can be applied to assess tissue microstructure at the early stage of disease. Single-shot DWI was performed with nine b-values. ROI on the vertebral body was independently measured in four parametric maps (Dslow, Dfast, f, Ff, where Ff is proton-density fat-fraction, Dslow represents the true diffusion coefficient, Dfast means the pseudodiffusion coefficient, and f stands for the perfusion fraction, which represents the relative proportion of the vascular compartment in marrow space). Logistic regression with stepwise selection was used with Ff, Dslow, Dfast, and f as inputs. Ff was significantly different between comparisons of ISS-1 vs. ISS-2, ISS-2 vs. ISS-3, and ISS-1 vs. ISS-3. Dslow was only different between comparisons of ISS-1 vs. ISS-3,