Dissertation
Dissertation > Medicine, health > Internal Medicine > Digestive and abdominal diseases > Pancreatic diseases

Autoimmune Pancreatitis:Study of CT and MRI Findings

Author NiRuiJun
Tutor XuShunLiang; RuanLingXiang
School Zhejiang University
Course Medical Imaging and Nuclear Medicine
Keywords Autoimmune pancreatitis CT MRI
CLC R576
Type Master's thesis
Year 2011
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Objective:Investigate the CT and MR imaging findings of autoimmune pancreatitis (AIP), to improve the comprehensibility and imaging diagnosing level of AIP, and to decrease imaging misdiagnosing of AIP.Methods:The data of CT and/or MR images of16patients with AIP were retrospectively reviewed. Plain CT and MR scanning and dynamic contrast-enhanced scanning was performed on13and8patients respectively, both CT and MR examinations on5patients. MR plain scanning sequences includes T2WI (fat-suppressed or not), T1WI, in-and out-phase T1WI. The location, shape of abnormal pancreas and the shape of boundary between normal and abnormal pancreas of segmental AIP were analyzed(in this text, the boundary is called’front-end’of abnormal pancreas, and the abnormal pancreas between the boundary and the most bulky abnormal pancreas is called ’forepart’). The density and signal model of abnormal pancreas parenchyma were analyzed. The CT attenuation value and MR signal intensity value of the pancreatic parenchyma of AIP and normal pancreas in plain scanning, the arterial phases, portal vein phases and delayed phases was measured. The mean CT attenuation value and MR signal intensity value of the pancreatic parenchyma in patients with AIP was compared with that in patients with a normal pancreas(n=25) respectively; at the same time, the mean CT attenuation value of segmental AIP was compared with that of pancreatic carcinoma(n=25) and pancreatic endocrine tumor(n=16). Analyze the imaging findings of extrapancreatic lesion of AIP.Results:Diffuse swelling of the pancreas was seen in7patients and segmental enlargement of pancreas in9patients. The tiny front-end and cone-shaped forepart was seen in3patients with segmental AIP, mimic bullet-point forepart at one side and the cone-shaped forepart at another side of abnormal pancreas in1of3patients; the flat front-end and trapezoid forepart in2patients with segmental AEP; the arcuate front-end and mimic bullet-point forepart in4patients with segmental AIP. Global shape: fusiform body of abnormal pancreas was seen in4patients with segmental AIP; irregular columnar body of abnormal pancreas with coarse edge in3patients with segmental AIP; sphericity shape in2patients with of segmental AIP (involved pancreatic head); sausage body of abnormal pancreas in1patient with segmental AIP; sausage body of abnormal pancreas in7patients. Abnormal pancreas showed homogeneous density, and the mean CT attenuation value of the abnormal pancreatic parenchyma was slightly lower than that of control group on plain scanning; the signal intensity on every sequence was lower than that of normal pancreas or multi-scale hypointensity:abnormal pancreas showed homogeneous hypointensity on fat-suppressed (or not) T2WI and not fat-suppressed T1WI, heterogeneous multiscale hypointensity on fat-suppressed T1WI. Some funicular slightly hyperintensity area could be seen in the abnormal pancreas on fat-suppressed T1WI. The progressive enhancement was found in16patients with AIP, different from the controled group of normal pancreas. The mean CT attenuation value and mean MR signal intensity value of the abnormal pancreatic parenchyma is significantly lower than that of control group in arterial phase (the mean CT attenuation value of endocrine tumor group is higher than and that of carcinoma is lower than that of control group), slightly higher than that of control group in portal vein phase (the mean CT attenuation value of endocrine tumor group is higher than and that of carcinoma is lower than that of control group too); the mean MR signal intense value higher than that of control group in delayed phase (8patients examined by MRI). Funicular and micronodular enhanced area could be seen head of time in6of8patients with AIP examined MR dynamic contrast-enhanced scanning. The pseudocapsule was seen in10patients with AIP (segmental pseudocapsule in6and capsule-rim like in4); the spleen arterial artery (and/or vein) involved in5patients (no displacement seen in the involved blood-vessel, the centric narrow blood-vessel in1of5,the vessel wall serration in1of5); the dilatate bileduct in5patients (the bile duct wall thickening in1of5); renal involvemed in2patients (nodular lesion), the mesentery involved(massive lesion) and retroperitoneal fibrosis in1patient. All of the extrapancreatic hyperplasia lesion manifesting homogeneous and progressing enhancement.Conclusion:Abnormal pancreas of AIP may represent various shape, whereas there is some distinctive CT and MR imaging manifestations. Dynamic contrast-enhanced scanning plays an important role in differentiating diagnosis between AIP and other massive lesion. The extrapancreatic lesion is common except for pancreas involvement and can mimic those of other diseases or play a important pole in diagnosing AIP. AIP can be diagnosed correctly through CT and MR examination.

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