Diffusion-weighted magnetic resonance imaging in autoimmune pancreatitis

• DOI: 10.1007/s11604-008-0311-2
• Publication Date: 2009-11-17T00:10:52Z
• Authors: Takao Taniguchi; Hisato Kobayashi; Koji Nishikawa; Etsushi Iida; Yoshihiro Michigami; Emiko Morimoto; Rikiya Yamashita; Ken Miyagi; Motozumi Okamoto
• Keywords: Male; Middle Aged; Autoimmune Diseases; 3. Good health; 03 medical and health sciences; Diffusion Magnetic Resonance Imaging; 0302 clinical medicine; Pancreatitis; Case-Control Studies; Immunoglobulin G; Humans; Female; Steroids; Tomography, X-Ray Computed; Aged

The aim of this study was to investigate the usefulness of diffusion-weighted magnetic resonance imaging (DWI MRI) for the diagnosis and evaluation of autoimmune pancreatitis (AIP).A total of 4 consecutive patients with AIP, 5 patients with chronic alcoholic pancreatitis (CP), and 13 patients without pancreatic disease (controls) were studied. DWI was performed in the axial plane with spin-echo echo-planar imaging single-shot sequence. Apparent diffusion coefficients (ADCs) were measured in circular regions of interest in the pancreas. In AIP patients, abdominal MRI was performed before, and 2-4 weeks after steroid treatment. Follow-up study was performed chronologically for up to 11 months in two patients. The correlation between ADCs of the pancreas and the immunoglobulin G4 (IgG4) index (serum IgG4 value/serum IgG4 value before steroid treatment) was evaluated.In the AIP patients, DWI of the pancreas showed high signal intensity, and the ADCs of the pancreas (mean +/- SD: 0.97 +/- 0.18 x 10(-3) mm(2)/s) were significantly lower than those in patients with CP (1.45 +/- 0.10 x 10(-3) mm(2)/s) or the controls (1.45 +/- 0.16 x 10(-3) mm(2)/s) (Mann-Whitney U-test, P < 0.05). In one AIP patient with focal swelling of the pancreas head that appeared to be a mass, DWI showed high signal intensity throughout the pancreas, indicating diffuse involvement. The ADCs of the pancreas and IgG4 index were significantly inversely correlated (Spearman's rank correlation coefficient, r (s) = -0.80, P < 0.05).Autoimmune pancreatitis showed high signal intensity on DWI, which improved after steroid treatment. ADCs reflected disease activity. Thus, diffusion-weighted MRI might be useful for diagnosing AIP, determining the affected area, and evaluating the effect of treatment.