MRI血氧水平依赖成像评价正常大鼠肾脏氧合水平的重复性研究

目的 探讨用MR血氧水平依赖(BOLD)成像评价大鼠肾脏氧合水平的重复性和科学性.方法5只健康雄性Wistar大鼠,扫描前称量大鼠体重,在3.0 T MR扫描仪上分别在第1天(d1)、第5天(d5)、第10天(d10)、第30天(d30)和第50天(dS0)行BOLD成像,测量表观自旋-自旋弛豫率(R2*).在d30和d50扫描完成后,注射呋塞米10 min后再次扫描,计算注药前后R2*的差值(△R2*).对5次扫描的R2*进行重复测量方差分析,对d30和d50注射呋塞米前后的皮、髓质R2*和皮、髓质△R2*进行配对t检验,观察呋塞米对皮、髓质R2*的影响并评价△R2*的重复性.结果d1、d5、d10、d30和d50大鼠体重分别为(150.4±3.7)、(170.2±7.0)、(201.0±5.8)、(306.2±17.0)和(352.0±12.2)g,差异有统计学意义(F=422.103,P＜0.01);肾脏皮、髓质R2*值差异均无统计学意义(P＞0.05).d30皮、髓质R2*在注射呋塞米前分别为(25.2±1.2)和(32.8±2.2)Hz,注射后分别为(21.1±2.2)和(25.9±3.0)Hz,皮、髓质R2*在注射呋塞米后均降低(P＜0.01);d50皮、髓质R2*在注射呋塞米前分别为(25.9±0.8)和(34.3±3.9)Hz,注射后分别为(20.2±1.5)和(27.0±3.2)Hz,皮、髓质R2*在注射呋塞米后均降低(P＜0.01).d30皮、髓质△R2*值分别为(4.1±1.7)和(6.9±2.8)Hz,d50皮、髓质△R2*值分别为(5.8±1.1)和(7.3±2.8)Hz,2次检查皮、髓质的AR2*差异均无统计学意义(P＞0.05).结论 大鼠肾脏皮、髓质基础R2*值在50 d内稳定,不受体重影响;在3.0 T MR上,应用呋塞米后大鼠肾脏皮、髓质R2*值均降低.

Reproducibility of measuring renal oxygenation by blood oxygen level-dependent MRI in rat

Objective To evaluate the reproducibility of measuring renal oxygenation in rat using blood oxygen level-dependent MR imaging(BOLD MRI).Methods Five intact male Wistar rats were included in this study and their body weights were measured before MRI scans.BOLD MRI were performed ou day 1(d1),day 5(d5),day 10(d10),day 30(d30)and day 50(d50)on a 3.0 T MR scanner to measure the apparent spin-spin relaxation(R2*).On d30 and d50,the differences of R2*(△R2*)were calculated between before and 10 min after furosemide injection through the tail vein.The reproducibility of the baseline R2* of 5 times repeated scans were verified by the repeated-measure ANOVA test.The R2* and △R2* between pre-and post-furosemide iniection on d30 and d50 were measured on the codex and the medulla and a paired t test was run to analyze their responses to furosemide and the reproducibility of △R2*.Results The average body weight on d1,d5,d10,d3 and d50 was(150.4±3.7)g、(170.2±7.0)g、(201.0±5.8)g、(306.2±17.0)g and(352.0±12.2)g,respectively,with statistical difference(F=422.103.P＜0.01).The R2* showed no statistical difference in the cortex and medulla among the five scans(P＞0.05).On d30.the R2* of the cortex and medulla was(25.2±1.2)and(32.8±2.2)Hz before and significantly decreased to(21.1±2.2)and(25.9±3.0)Hz after furosemide administration,respectively(P＜0.01).On d50,the R2* of the cortex and medulla was(25.9±0.8)and(34.3±3.9)Hz before and significantly decreased to(20.2±1.5)and(27.0±3.2)Hz after furosemide administration.respectively(P＜0.01).The △R2* on the codex and medulla was(4.1±1.7)and(6.9 4-2.8)Hz on d30 and(5.8±1.1)and(7.3±2.8)Hz on d50,respectively,but there is no significant difference between eortex and medulla(P＞0.05).Conclusion The baseline R2* in the cortex and medulla were reproducible over 50 days and they were not body weighted.On 3.0 T MR scanners.R2* in the codex and medulla decreased significantly after administration of furosemide.