Diffusion-weighted Whole-body Imaging with Background Body Signal Suppression Enables Simultaneous Whole-body Assessments of IgG4-related Diseases.

Objective IgG4-related disease (IgG4-RD) is a systemic condition that frequently involves multiple organs. This study examined the utility of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) for the diagnosis and monitoring of IgG4-RD. Methods Twenty patients underwent DWIBS for the diagnosis of IgG4-RD. Of these, six did so after steroid therapy. The extent of high-intensity areas visible on DWIBS was compared to that on computed tomography (CT). Changes in signal enhancement and apparent diffusion coefficient (ADC) values on DWIBS were analyzed following steroid therapy. Results In addition to 20 main IgG4-RD lesions, areas of high intensity were detected on DWIBS in 28 lesions in 8 organs and the retroperitoneum. The high-intensity areas on DWIBS also appeared as a mass or thickness on CT, except in three areas in the kidneys and retroperitoneum, but segmental wall thickness of the bile duct in two patients was undetectable on DWIBS. On the second DWIBS procedure following steroid therapy, all 16 high-intensity areas displayed some degree of improvement, including complete resolution (n=3), disappearance of high signal intensity and a decrease in the size of the lesion (n=6), and a decrease in both signal intensity and lesion size (n=7). Furthermore, the ADC value of 13 areas significantly increased after steroid therapy (1.32±0.24×10 mm/s vs. 1.68±0.25×10 mm/s; p<0.05). Conclusion DWIBS can readily detect IgG4-RD lesions throughout the body simultaneously and provide information about disease activity and therapeutic effects. DWIBS is an indispensable tool in the treatment of IgG4-RD.