Fig. 4
A 56-year-old male with multiple myeloma demonstrating additional benefit of DWI in the evaluation of clinical objective response. MRI taken before chemotherapy (a) shows a 4.0 × 3.1 cm enhancing mass at posterior arc of left 9th rib. Axial DWI (b = 900) and ADC map show marked diffusion restriction in the lesion (mean ADC value: 0.54 × 10− 3 mm2/s). Coronal diffusion MIP image (b = 900) shows diffuse high signal intensity involving whole axial skeletons, suggesting diffuse bone marrow involvement. After 4 cycles of chemotherapy, follow-up MRI (b) shows equivocal change in the tumor size (3.7 × 2.3 cm) in the left 9th rib. Axial DWI (b = 900) and ADC map show marked improvement of diffusion restriction in the lesion (mean ADC value: 1.54 × 10− 3 mm2/s). Coronal diffusion MIP image (b = 900) demonstrates decreased signal intensity in the axial skeletons, suggesting good response to the treatment. Based on RECIST 1.1 or MDA criteria, this patient is classified as imaging SD. However, when DWI findings are considered in MDA-DWI criteria, this patient is classified into imaging PR