摘要目的：探讨P选择素为靶标的磁共振靶向对比剂（P-Gd-probe）在大鼠急性胰腺炎（AP）病情轻重分级中的应用。方法采用腹腔注射L-精氨酸溶液（100 mg／100 g体重）3次、间隔1 h的方法制备SD大鼠AP模型，对照组注射等容积生理盐水，依照病理结果将AP大鼠分为急性水肿性胰腺炎（ AEP，造模后6、12 h）组及急性坏死性胰腺炎（ ANP，造模后24、48 h）组。造模6、12、24、48 h大鼠及对照组大鼠行磁共振T1加权横断位平扫及增强扫描，对比剂采用P-Gd-probe。测量增强前后胰腺部位的信号声噪比（ SNR）。扫描完成后取胰腺组织行病理学检查，采用免疫组织化学方法检测胰腺组织P选择素表达。结果造模6h后胰腺组织出现炎症改变，且炎性程度随造模时间延长而加重，胰腺组织P选择素蛋白表达也随AP的炎性程度加重而增高。对照组增强前后胰腺组织SNR值基本不变；AEP组增强前后SNR值分别为17．22±1．35、37．38±1．66，ANP组分别为16．29±1．39、58．18±1．03，这两组增强后的 SNR 值均显著高于增强前，差异均有统计学意义（ t 值分别为－49．59、－86．09， P 值均＜0．001）。结论 MRI时选择P选择素为靶标的单克隆抗体靶向对比剂有助于对AP病情严重程度的判断。

abstractsObjective To investigate the application of MRI targeting contrast agent ( P-Gd-Probe) for P selectin in evaluating the severity grades of acute pancreatitis (AP).Methods L-arginine solution (100mg/100kg) were intraperitoneally injected for 3 times once an hour to establish AP model in SD rats. Control group was injected with normal saline in a equal volume .All rats were divided into acute edematous pancreatitis (AEP) group (6 h and 12 h after model establishment)and acute necrotizing pancreatitis (ANP) group (24 h and 48 h after model establishment ) based on the pathology .The rats were examined by T 1 WI plain and enhanced scanning at 6 h, 12 h, 24 h and 48 h after injection , and P-Gd-probe was as the enhanced contrast agent.The signal noise ratio ( SNR) of the pancreas were measured before and after enhancement .Then the pancreas tissues were harvested for pathological examination and P selectin expression in pancreatic tissue was detected using immunohistochemical analysis .Results Inflammation was observed in pancreatic tissue at 6h after establishment , and became more serious as the modeling time extended .P selectin expression was increased as pancreatitis inflammation became more serious .The SNR of control group was stable before and after enhancement.The SNR before and after enhancement was 17.22 ±1.35 and 37.38 ±1.66 in AEP group,&nbsp;and 16.29 ±1.39 and 58.18 ±1.03 in ANP group.The SNR after enhancement was higher than that before enhancement, and the differences were significantly different ( t=-49.59 and -86.09, P<0.001 ). Conclusions Monoclonal antibody MRI contrast agent targeting P selectin is helpful in evaluating the severity of AP.