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

Abstract

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. Key words: Kidney codex; Kidney medulla; Magnetic resonance imaging; Animals,laboratory