Diffusion-weighted magnetic resonance imaging in autoimmune pancreatitis.
OBJECTIVE
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).


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 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).


CONCLUSIONS
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.
Department of Internal Medicine, Ohtsu Red Cross Hospital, 1-1-35 Nagara, Ohtsu, 520-8511, Japan. ttng8511@yahoo.co.jp
Takao
T
Taniguchi
Hisato
H
Kobayashi
Koji
K
Nishikawa
Etsushi
E
Iida
Yoshihiro
Y
Michigami
Emiko
E
Morimoto
Rikiya
R
Yamashita
Ken
K
Miyagi
Motozumi
M
Okamoto
D000368:Aged; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000188:drug therapy; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D010195:Pancreatitis / Q000175:diagnosis* / Q000188:drug therapy; D013256:Steroids / Q000627:therapeutic use; D014057:Tomography, X-Ray Computed
D007074:Immunoglobulin G; D013256:Steroids