Diffusion-weighted magnetic resonance imaging in autoimmune pancreatitis |
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Authors: | Takao Taniguchi Hisato Kobayashi Koji Nishikawa Etsushi Iida Yoshihiro Michigami Emiko Morimoto Rikiya Yamashita Ken Miyagi Motozumi Okamoto |
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Institution: | (1) Department of Internal Medicine, Ohtsu Red Cross Hospital, 1-1-35 Nagara, Ohtsu 520-8511, Japan;(2) Department of Radiology, Ohtsu Red Cross Hospital, Ohtsu, Japan |
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Abstract: | Purpose 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).
Materials and methods 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.
Results In the AIP patients, DWI of the pancreas showed high signal intensity, and the ADCs of the pancreas (mean ± SD: 0.97 ± 0.18
× 10−3 mm2/s) were significantly lower than those in patients with CP (1.45 ± 0.10 × 10−3 mm2/s) or the controls (1.45 ± 0.16 × 10−3 mm2/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).
Conclusion 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.
T. Taniguchi and H. Kobayashi contributed equally to this study |
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Keywords: | Autoimmune pancreatitis Diffusion-weighted magnetic resonance imaging Steroid treatment |
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