急性肾衰肾内氧代谢的血氧水平依赖功能磁共振评价

Evaluation of kidney oxygen bioavailability in acute renal failure by blood oxygen level dependent magnetic resonance imaging

目的:应用磁共振血氧水平依赖成像(BOLD MRI)对急性肾衰肾内的氧代谢进行评价。方法:20名志愿者作为正常对照组,急性肾衰患者21例,其中少尿期18例,非少尿型1例,功能性急性肾衰竭2例。常规轴位T2WI、T1WI以及BOLD MRI扫描。BOLD MRI为冠状位16个梯度回波序列成像,分别测量肾脏的皮质及髓质的R2*值以及计算髓质与皮质的R2*比值,并将各组数据进行对比分析。结果:正常组肾髓质R2*值(17.64±1.86)明显高于皮质R2*值(13.73±0.49),P<0.00,髓皮质R2*值比值为1.28±0.06。急性肾衰少尿组肾皮质R2*值(12.25±2.41)和髓质R2*值(13.31±4.28)以及髓皮质比值(1.01±0.25),与正常组比较均减低,P<0.05。功能性急性肾衰竭与急性间质性肾炎非少尿期患者的肾皮、髓质R2*值,以及髓皮质比值,均高于正常组。结论:肾脏BOLD MRI测量的R2*值可评价肾脏急性肾衰时氧代谢的改变。在急性肾衰少尿期,皮质及髓质内氧的利用率减低,髓皮质氧浓度梯度差消失。

Objective： To assess the kidney oxygen bioavailability in acute renal failure using blood oxygen level dependent（BOLD） magnetic resonance（MR） imaging.Methods： Twenty-one patients with acute renal failure,including 18 patients with oliguric renal failure,1 nonoliguric acute renal failure and 2 functional renal failure were enrolled in the study;20 healthy subjects served as controls.All subjects received renal functional MR examination.BOLD MR imaging with 16 gradient-recalled-echoes on a 1.5-T scanner were performed.R2＊（1/sec） values of the cortex and medulla and R2＊ ratio of the medulla to cortex（R2＊ ratio of M/C） of the renal were recorded respectively.Results： The R2＊ values of the medulla was higher than those of the cortex in controls（17.64±1.86/sec vs 13.73±0.49/sec,P0.00）.The R2＊ ratio of M/C in controls was 1.28±0.06.The R2＊ values of the medulla（13.31±4.28/sec） and cortex（12.25±2.41/sec） and the R2＊ ratio of M/C（1.01±0.25） in oliguric renal failure were lower than those in controls（P 0.05）.Patients with functional renal failure and nonoliguric acute renal failure had higher R2＊ values in cortex and medulla and higher R2＊ ratio of M/C than those of controls.Conclusion： BOLD MRI demonstrates that decreased R2＊ values of cortex and medulla suggest lower oxygen bioavailability in acute renal failure and decreased R2＊ ratio of M/C suggests the disappearance of a steep cortico-medullary gradient of oxygen.