MRI在胰腺局灶性脂肪浸润的诊断价值

目的探讨胰腺局灶性脂肪浸润的MRI典型表现。方法回顾性分析MRI诊断胰腺局灶性脂肪浸润病人12例,除常规序列外,加扫化学位移成像序列,观察同、反相位图像组织信号变化情况,以确定有无脂肪浸润改变。所有病例MRI检查前均经CT平扫和/或增强扫描,因CT表现缺少特异性,不能明确低密度病灶性质而建议进一步检查,所有病例经随访5～36个月(平均16个月)无明显变化。结果12例胰腺局灶性脂肪浸润主要累及胰头和钩突前部,5例合并不同程度胰腺颈、体、尾部脂肪浸润,但仍以胰头和钩突前部脂肪浸润最明显。胰腺局灶性脂肪浸润区域在常规压脂T1WI、T2WI上9例未见明显异常信号,3例与周围正常胰腺对比呈稍低信号;在化学位移成像序列中,局灶性脂肪浸润区域在同相位上与周围正常胰腺对比呈等或稍高信号,而在反相位上局灶性脂肪浸润区域则较同相位上出现中度到明显不均匀信号下降,从而确立胰腺局灶性脂肪浸润诊断。结论胰腺局灶性脂肪浸润主要累及胰头和钩突前部或以此区域更明显,MRI化学位移成像具有典型表现,对胰腺局灶性脂肪浸润诊断具有重要价值。

MR imaging in diagnosis of focal fatty infiltration of the pancreas

Objective To investigate the MR characteristics of focal fatty infiltration of the pancreas.Methods Retrospectively reviewed the MR images of twelve patients with focal fatty infiltration of the pancreas.For MR examination,plain scanning with chemical shift imaging sequence was performed except routine sequences.Compared the alteration of signal intensity on in-phase and opposed-phase images,we could determine whether focal fatty infiltration exists easily.CT examination was performed before MRI examination in all patients also.Follow-up MR scans were obtained in all patients at 5-36 months(mean,16 months)after the initial examination,it showed no obvious variation within the initially fatty infiltration regions of pancreatic parenchyma.Results Focal fatty infiltration of the pancreas was dominantly located at the anterior aspect of the head and uncinate process of the pancreas.Although 5 patients combined with differential degree of fatty infiltration in the pancreas neck,body and tail,it was more severe in the anterior aspect of the head and uncinate process of the pancreas.Focal fatty infiltration region of pancreatic parenchyma showed normal or high signal intensity comparing with the surrounding normal pancreas on in-phase T1-weighted images,showed moderate to marked signal intensity loss on opposed-phase gradient-echo images in all patients,and had a normal appearance on T1-weighted and T2-weighted images with fat-saturated in 9 patients or had a slight hypointense comparing with the surrounding pancreatic parenchyma in 3 patients.Conclusion Focal fatty infiltration of the pancreas was dominantly located at or more severe in the anterior aspect of the head and uncinate process of the pancreas.The MR characteristics of focal fatty infiltration of the pancreas is definite.Chemical shift imaging sequence has important value in the diagnosis of focal fatty infiltration of the pancreas.