Diagnosis and differential diagnosis value of magnetic resonance imaging in autoimmune pancreatitis / 中华消化杂志

ABSTRACT

Objective To investigate the diagnosis and differential diagnosis value of multisequences magnetic resonance imaging (MRI) in autoimmune pancreatitis (AIP).Methods The MRI data of twelve AIP patients were retrospectively analyzed.The sequences of MRI included T1 weighted imaging,T2-weighted imaging,magnetic resonance cholangiopancreatography (MRCP),diffusionweighted imaging (DWI) and dynamic enhancement images.The location and involving extent of lesions,signal,patterns of dynamic enhancement,changes of pancreatic and biliary duct,pseudo-capsule sign and other accompanying signs were observed.Twelve pancreatic cancer patients and twelve other patients with normal pancreas were set as controls.The imaging signs of AIP group and pancreatic cancer group were compared with Fisher's exact test.On the sequence of DWI,the apparent diffusion coefficient (ADC) values of pancreatic interested region of the three groups were tested and compared with least significant difference t test.At each period of enhanced MRI,the intensity ratios of pancreatic interested region to the left paraspinal muscle at the same level of the three groups were measured and compared with Pillai's Trace test.Results Among 12 patients with AIP,seven were diffused lesion,four were localized lesion,and one was multiple lesions.Among 12 pancreatic cancer patients,one was diffused lesion,and eleven were localized lesion.The difference of these two groups was statisfically significant (Fisher's exact test,P＜0.01).Among 12 AIP patients,on the T1-weighted image,intensity decreased in nine lesions,two cases without obvious intensity decreasing,and one case unevenly increased.On the T2 weighted image,intensity slightly increased in nine lesions,equal in one case,and slightly lowered in two cases.The ADC value of the lesions of AIP group ((1.011 ± 0.118) × 10 3 s/mm2) was lower than that of normal pancreas group ((1.489 ± 0.072) × 10 3 s/mm2) and pancreatic cancer group ((1.274 ± 0.120) × 10 3 s/mm2),and the differences were statistically significant (t=-11.793,-4.300; both P＜0.01).Among 12 AIP patients,the pancreatic duct of the lesions was irregular segmental sclerosis and stenosis in four patients.Pseudo-capsule sign around the lesions of pancreas was seen in seven patients.Among 12 pancreatic cancer patients,the pancreatic duct of the lesions was stenotic in two patients while the pseudo-capsule sign wasn't found.The differences of these two groups were statistically significant (Fisher's exact test,both P＜0.01).Dynamic enhanced MRI showed that enhancement patterns of the lesions of both AIP and pancreatic cancer presented progressive enhancement.However,during the balanced period,the signal intensity ratio of AIP group (3.34±1.40) was significantly higher than that of pancreatic cancer group (2.38 ± 0.18),and the difference was statistically significant (F =60.703,P ＜ 0.01).Conclusion Combination of a variety of sequences of MRI can help to fully reflect the pathological and biological characteristics of AIP and increase the accuracy of diagnosis.