基于Dixon技术的胰腺脂肪分数测量方法及其与临床指标的相关性

MRI measurement of pancreatic fat fraction based on Dixon method and correlation analysis with clinical factors

目的探讨基于Dixon技术胰腺脂肪分数（PFF）的测量方法及其与临床指标的相关性。方法回顾性分析2015年7月至2016年6月苏州大学附属第一医院彩色超声多普勒示胰腺回声分布均匀，MRI示胰腺信号均匀的95例受检者。记录年龄，测量血压、身高、体质量，计算体质量指数（BMI）。抽取静脉血，测定空腹血糖（FPC）、总胆固醇（TC）、甘油三酯（TG）、低密度胆固醇（LDL-c）和高密度胆固醇（HDL-c）。行腹部横轴面Dixon水脂分离T1WI、压脂T2WI、DWI和冠状面T2WI序列扫描，测量PFF和第4、5腰椎间隙平面以上8 cm处腹腔横断面的皮下脂肪面积（SA）、腹腔内脏脂肪面积（VA）、腹部总脂肪面积（TA），计算腹部皮下脂肪面积比例（SFP）以及腹部内脏脂肪面积比例（VFP）。95例受试者的PFF为2.1%~35.0%，中位数为8.9%。根据PFF结果将受检者分为胰腺低脂肪组（PFF≤8.9%，n=51）与胰腺高脂肪组（PFF〉8.9%，n=44）。采用独立样本t检验比较低、高脂肪组间临床指标的差异，采用Pearson线性相关分析评价临床指标和PFF的相关性。结果95例受试者均获得满意的同相位、反相位、水像和脂像图像，所有胰腺的MRI图像信号均匀，解剖结构清晰，无明显运动伪影。胰腺高脂肪组的BMI、收缩压、TG、LDL-c、FPC、VA、TA、VFP均高于低脂肪组，SFP低于低脂肪组，差异均有统计学意义（P均〈0.05）；年龄、舒张压、HDL-c、TC、SA的差异无统计学意义（P均〉0.05）。年龄、BMI、收缩压、舒张压、TG、LDL-c、FPC、SA、VA、TA、VFP水平与PFF呈低到中度正相关（r值为0.219~0.515，P均〈0.05），SFP水平与PFF呈中度负相关（r=－0.434，P〈0.01）。结论采用Dixon技术对PFF进行测量方法可行，PFF与年龄、BMI、血压、腹部脂肪面积以及血脂代谢指标具有一定的相关性。

ObjectiveTo analyze the pancreatic fat fraction based on magnetic resonance Dixon sequence and correlation with clinical factors.MethodsA total of 95 cases of adult physical examinees who had underwent abdominal MRI were retrospectively studied. Age, blood pressure, height and weight were recorded for every subject, and BMI was then calculated. The venous blood sample were analyzed for fasting plasma glucose （FPC）, total cholesterol （TC）, triglycerides （TG）, low density lipoprotein-cholesterol （LDL-c） and high density lipoprotein-cholesterol （HDL-c）. All cases underwent water-fat separation T1WI, fat inhibition T2WI, DWI, and coronal T2WI scans. We measured PFF of all the examinees, subcutaneous fat area （SA）, visceral fat area （VA）, and total abdominal fat area （TA） on the images above 8 centimeter of L4 to L5 were also measured, subcutaneous fat percentage （SFP） and visceral fat percentage （VFP） were further calculated. PFF of the 95 cases ranged from 2.1% to 35.0%, and the median PFF was 8.9%. This cohort was divided into low-fat pancreas groups （PFF≤8.9%, n=51） and high-fat pancreas group （PFF〉8.9%, n=44） according to the median PFF. Independent sample t test was used to test for differences in clinical index between the two groups, Pearson correlation coefficient was used to measure the strength of a linear association between clinical indexes and PFF.ResultsExcellent water only, fat only, in phase and out of phase images of all the 95 adults were obtained. Signals of MRI images of all pancreas were homogeneous, the anatomic structures of all images were sharp and clear, and all the images had no motion artifact. The levels of BMI, systolic blood pressure, TG, LDL-c, FPC, VA, TA, VFP of high-fat pancreas group were significantly higher than those of low-fat pancreas group, and SFP was lower （P〈0.05）. The differences in age, diastolic blood pressure, HDL-c, TC, and SA between the two groups were not statistically significant（P〉0.05）. PFF was weakly to moderately positively correlated with age, BMI, systolic blood pressure, diastolic blood pressure, TG, LDL-c, FPG, SA, VA, TA and VFP （r=0.219 to 0.515, P〈0.05）, SFP was moderately negatively correlated with PFF（r=-0.434, P〈0.01）.ConclusionsIt＇s feasible and accurate to measure the PFF with Dixon technique. PFF have a certain correlation with age, BMI, blood pressure, abdominal fat area and blood lipid metabolism.