胰泌素增强磁共振扩散加权成像测定成人正常胰腺外分泌功能

Assessment of exocrine pancreatic function by secretin stimulated diffusion weighted imaging in healthy adult

目的探讨胰泌素增强磁共振扩散加权成像（S-DWI）对成人正常胰腺外分泌功能的评估价值。方法招募20名健康志愿者，其中男性13例，女性7例，年龄（38±9）岁；BMI为（22．89±2．95）kg／m^2。采用美国GESignaExcite3．0T超导型MR仪行胰腺横断平扫T1WI、T2WI、DWI扫描，后经静脉注入胰泌素0．1ml／kg，获取注射胰泌素前（0min）及注射后1、3、5、7、9、11min的DWI图像。由两名放射科医师观察注射胰泌素前、后胰管的变化情况，测量胰头、体、尾部表观扩散系数（ADC）值，ADC峰值及其增加的百分比，达峰时间。以粪弹力蛋白酶（FE-1）含量为外分泌功能评估的参照标准。两名医师测量结果间的比较采用配对样本t检验；注射胰泌素前及注射后各时间点胰头、体、尾部ADC值比较采用单因素方差分析法；FE-1含量与注射胰泌素后ADC平均峰值间的相关性采用Person相关性检验。结果两名医师测量的ADC均值的差异无统计学意义。20名志愿者注射胰泌素前的胰腺ADC值为（1．60±0．21）×10^-3mm^2／s，ADC峰值为（2．70±0．25）×10^-3mm^2／s，较注射前的基线值增加（72±25）％，平均达峰时间为（2．97±0．88）min，后又逐渐降至接近注射前的基线值。注射胰泌素后0、1、3、5、7、9、11min的胰头、体、尾部ADC值差异均有统计学意义（P值均=0．0001），但同一时间点胰头、体、尾部间的ADC值差异均无统计学意义。20名志愿者FE一1含量为341．2～673．2μg／g，平均（537．2±80．2）μg／g。FE-1含量与注射胰泌素后ADC平均峰值间具有显著的相关性（r=0．87，P=0．0001）。结论胰泌素增强磁共振扩散加权成像可以反映成人正常胰腺的外分泌功能。

Objective To characterize and quantify exocrine pancreatic function by secretin stimulated diffusion weighted imaging （DWI） in healthy subjects. Methods The present study includes 20 health volunteers composed of 13 male and 7 female with a median age of （38 ± 9 ） years and median BMI of （22.89 ± 2.95 ）kg/m2. All subjects underwent MR imaging at 3.0 T device （Signa EXCITE, GE Heahhcare）. Axial TI and T2 weighted sequences and the diffusion weighted sequence was acquired prior to administration of secretin （0 min） and 1, 3, 5, 7, 9, and 11 rain after administration of secretin. A bolus of secretin was injected intravenously at a dose of 1 mL/kg body weight. The changes of pancreatic duct, baseline and peak apparent diffusion coeffcient （ ADCs ） values of pancreatic head, body and tail, and the percentage increase over the baseline ADCs, and time to peak ADCs were measured by the two radiologists. The feces elastase 1 （ FE 1 ） test was used to determine the pancreatic exocrine reserve of all subjects. The comparisons of the two radiologists on the ADC measurements were determined by t test. Inter-group differences of ADC of pancreatic head, body and tail before administration of secretin, after administration of secretin, were compared each of the segments using multivariate analysis of variance （ANOVA）. The correlation between FE 1 and the peak ADCs was analyzed by using Pearson＇s correlation test. Results There were no statistically significant differences of all ADCs between the two radiologists. The baseline ADCs of the 20 healthy subjects before administration of secretin was （ 1.60 ±0.21 ） × 10^ -3 mm2/s, and the peak ADC was （2.70 ± 0.25 ） × 10^ -3 mm2/s, which increased by （72 ± 25 ） %, the time to peak ADCs was （2.97 ± 0.88） min, then it gradually decreased to near baseline value before administration of secretin. The ADCs of pancreatic head, body and tail at 0, 1, 3, 5, 7, 9, 11 min after administration of secretin were statistically significant （ P = 0.0001 ）, but at each time point, the difference among ADCs of pancreatic head, body and tail was not statistically significant. The mean FE 1 of 20 healthy subjects was （537.2 ±80.17） μg/g （range 341.2 -673.2 μg/g）. A positive linear correlation was found between the mean peak ADCs after administration of secretin and FE 1 （ r = 0.87, P =0. 0001 ）. Conclusions Secretin stimulated DWI can reflect the exocrine pancreatic function in healthy adults.