基于mLIVE序列对青年人腹部脂肪分布及内脏脂肪定量评估的研究

Quantitative evaluation of abdominal fat distribution and visceral fat in young people based on mLIVE sequence

目的利用MRI多回波肝脏内插容积激发(multi echo liver interpolated volume excitation,mLIVE)序列评估健康成年人内脏脂肪面积(visceral fat area,VFA)、皮下脂肪面积(subcutaneous fat area,SFA)、肝脏、胰腺、肾脏及椎体的脂肪沉积程度及其之间的相关性。材料与方法纳入45例志愿者(女26例,男19例),测量身高、体质量,计算身体质量指数(body mass index,BMI)。对每位受试者行1.5 T MRI腹部轴位常规平扫和mLIVE扫描,两名观察者测量所有志愿者肝脏、胰腺、L2椎体、肾实质的脂肪分数(fat fraction,FF),并将mLIVE自动生成的FF图导入ImageJ软件,测量每位志愿者L2椎体层面的VFA和SFA。采用Pearson相关分析探究BMI与MRI测量指标,MRI测量指标之间的相关性。结果两名观察者所测数据一致性良好(组内相关系数>0.75);BMI与VFA(r=0.677,P<0.05)、SFA(r=0.781,P<0.05)相关性良好,但与肝脏和胰腺FF无相关性(P>0.05);VFA、SFA及胰腺FF均与肝脏FF相关(P<0.05),其中胰腺与肝脏的FF相关性最强(r=0.449,P<0.05);VFA与SFA具有相关性(r=0.575,P<0.05),VFA与L2椎体FF具有相关性(r=0.349,P<0.05)。结论BMI可以大致评估健康成年人脂肪组织分布的情况,但对腹部不同部位组织脂肪含量的评估却不够准确。VFA与肝脏FF相关性较好且呈中等强度正相关,由此可见腹部内脏脂肪增多对肝脏脂肪沉积的发生有重要意义。健康成年人肝脏与胰腺FF明显相关,说明肝脏脂肪沉积与胰腺脂肪沉积有密切联系。VFA与L2椎体FF正相关,提示腹型肥胖可能容易影响腰椎骨髓脂肪含量。我们的研究能够提供健康成年人不同器官及组织脂肪含量的关系,帮助进一步了解成年人的脂肪代谢,给临床上代谢综合征风险的预测及其早期预防提供更多信息和证据。

Objective:To quantitatively investigate the visceral fat area(VFA),subcutaneous fat area(SFA),the fat deposition of liver,pancreas,kidney and vertebral body in healthy adults by using multi echo liver interpolated volume excitation(mLIVE),and explore the relationship between them.Materials and Methods:Forty-five volunteers(26 females and 19 males)were recruited and scanned using mLIVE sequence.The height and the body weight of the volunteers were measured.The body mass index(BMI)and the fat fraction(FF)of liver,pancreas,kidney and vertebral body were calculated by two observers.VFA and SFA at the L2 vertebral body plane of each subject were measured using ImageJ software(U.S.Institute of Health)by two observers.Pearson correlation analyses were used to explore the relationship between BMI and MRI-derived fat measurements,and the relationship between MRI-derived fat measurements.Results:The data measured by the two observers were consistently good(intra-class correlation coefficients>0.75).Correlation analysis revealed that BMI were correlated significantly with VFA(r=0.677,P<0.05)and SFA(r=0.781,P<0.05).No correlations were found between BMI and the FF values of liver and pancreas(P>0.05).VFA,SFA and pancreas FF were correlated with the FF values of liver(P<0.05)respectively,and the pancreas FF had best correlation with the liver FF(r=0.449,P<0.05).VFA was correlated significantly with SFA(r=0.575,P<0.05)and vertebral FF(r=0.349,P<0.05),respectively.Conclusions:Although BMI can roughly evaluate the adipose tissue distribution in healthy adults,it is not accurate in estimating the fat content of internal organs.A positive correlation between VFA and the FF values of liver illustrating that the increased abdominal visceral fat play an important role in the occurrence of liver fat deposition.The FF of liver and pancreas was positively correlated in healthy adults demonstrating that liver fat deposition is of great significance on the pancreas fat deposition.The relationship between VFA and the FF values of lumbar vertebral indicating that abdominal obesity may easily affect the fat content of lumbar bone marrow.This study shed new light on the relationship between fat content in different organs and tissues of healthy adults,help further understand fat metabolism in healthy adults,and provide more information and evidence for clinical risk prediction and early prevention of metabolic syndrome.