MR血氧水平依赖成像评价兔输尿管梗阻肾纤维化的可行性

Feasibility of using blood oxygen level-dependent magnetic resonance imaging to evaluate renal fibrosis of ureteral obstruction of rabbits

目的探讨MR血氧水平依赖成像（MR—BOLD）评价兔输尿管梗阻肾纤维化的可行性。方法将40只健康新西兰大白兔随机分为对照组（n=8）和兔输尿管梗阻（UUO）组（n=32），UUO组再随机分成四组（每组8只）。UUO组实验兔完全结扎左肾输尿管近段建立UUO模型，分别于术前、术后2、4、6和8周行MR冠状T：加权成像（T2WI）和轴位BOLD扫描，分别对应为UUO2、UUO4、UUO6和UUO8周亚组。MR扫描后立即切除左肾并行病理组织学检查。在BOLD图像上测量计算皮质（C）的E弛豫率（CR2^＊）、髓质（M）的MR2^＊和同层面肌肉的R2^＊肌，计算C与M的标化财值（sR2^＊），以及C和M分别在UUO前后的sR2^＊的差值（△sR2^＊）。采用独立样本t检验比较对照组、UUO组每个时间点皮髓质的sR2^＊（sCR2^＊、sMR2^＊、sCR2^＊对照、sMR2^＊对照）的差异；对照组组内及UUO组组内sR2^＊的两两比较采用LSD检验；UUO 2周、4周、6周及8周每一亚组内皮髓质的△sR2^＊（△sR2^＊、△sMR2^＊）的比较采用独立样本t检验。结果UUO组各亚组的sR2^＊均低于对照组对应时间点的sR2^＊对照（P〈0．05），对照组与UUO组术前的sR2^＊比较无统计学差异（P〉0．05）。UUO 2、4、6及8周左肾sCR2^＊值分别为0．32±0．01、0．37±0．01、0．47±0．02和0．50±0．03；sMR2^＊值分别为0．39±0．02、0．48±0．02、0．58±0．04和0．65±0．05。左肾C带，UUO 2周与6周、8周比较，UUO 4周与6周、8周比较差异均有统计学意义（均P〈0．01）；左肾M带，UUO 2周与6周、8周比较，UUO 4周与8周比较差异均有统计学意义（均P〈0．01）。对照组各时间点之间sCR2^＊对照和sMR2^＊对照两两比较无明显差异（均P〉0．05）。UUO组各时间点左肾△sCR2^＊分别为0．31±0．02、0．20±0．02、0．14±0．20、0．09±0．04；△sMR2^＊分别为0．51±0．05、0．36±0．04、0．28±0．05、0．19±0．05。UUO 2、4及6周的△sCR2^＊均小于△sMR2^＊（P〈0．05）；UUO 8周的△sCR2^＊与△sMR2^＊差异无统计学意义（P〉0．05）。结论肾纤维化时肾髓质的R？变化较皮质显著，MR—BOLD可以反映。肾纤维化发生发展的过程，对评价输尿管梗阻肾纤维化具有可行性和较大价值。

Objective To investigate the feasibility of blood oxygen level-dependent MR （ MR- BOLD） in assessing renal fibrosis of ureteral obstruction of rabbits. Methods Forty healthy New Zealand rabbits were randomly divided into control group （n = 8 ） and unilateral ureteral obstruction （UUO） group （n = 32）. The rabbits in the UUO group were subjected to unilateral ureteral obstruction of the left kidney. Coronal T2 weighted imaging （ T2 WI） and axial BOLD examinations were performed before operation, 2, 4, 6 and 8 W after operation （ each subgroup n = 8 ）. After the examinations, nephrectomy was performed for histologic evaluation. The T2^＊ relaxation rate of the renal cortex （ CR2^＊ ） , medulla （ MR2^＊ ） and the same level of muscle（ R2^＊ muscle ） were measured separately. The normalization of the cortex and medulla （sR2^＊）, and the difference of sR2 between renal cortex and medulla before and post UUO （ AsR2^＊ ） were calculated. The differences of sR2^＊ （ sCR2^＊, sMR2^＊, sCR2^＊ control, sMR2^＊ control ） at each time point between control and UUO group were compared by using independent sample t test. The LSD test was used to compare the sR2^＊ in the control with that in the UUO group. The AsCR2^＊ and AsMR2^＊ values of the subgroups at UUO 2, 4, 6 and 8 W were compared by independent sample t test. Results The sR2^＊ values of UUO group were all lower than those of control group （ all P 〈 0. 05 ） , while sR2^＊ control and sR2 in UUO group before operation were not significant different （P 〉 0. 05）. The sCR2^＊ values of UUO 2, 4, 6 and 8 W were 0. 32 ± 0.01, 0.37 ±0.01, 0.47 ±0.02 and 0.50 ±0.03. The sMR2^＊ values were 0.39 ±0.02, 0.48 ±0.02, 0.58 ± 0. 04 and 0. 65 ± 0. 05. There were significant differences of sCR2 between UUO 2 W and 6 W, UUO 2 W and 8 W, UUO4 W and 6 W, UUO 4 W and 8 W （all P〈0.01）.There were significant differences of sMR2^＊ between UUO 2 W and 6 W, UUO 2 W and 8 W, UUO 4 W and 8 W （all P 〈0. 01）. No significant difference was founded between sCR2^＊ and sMR2 at each time point in control group （ P 〉 0. 05 ）. The AsCR2^＊ values of UUO 2, 4, 6 and 8 W were 0. 31 ±0.02, 0. 20 ±0. 02, 0. 14 ±0.20, 0. 09 ±0. 04; the △sMR2^＊ values were 0. 51 ±0. 05, 0. 36 ±0. 04, 0. 28 ±0. 05, 0. 19 ±0. 05. The △sCR2^＊ values of UUO 2, 4 and 6 W were less than △sMR2^＊ （ P 〈 0. 05 ）. There was no significant difference between AsCR2^＊ and △sMR2^＊ in UUO 8 W （ P 〉 0. 05 ）. Conclusions The R2^＊ change in medulla resulted from renal fibrosis is more significant than cortex. MR-BOLD can reflect the process of renal fibrosis. It＇s feasible and of great value to use renal MR-BOLD for the assessment of renal fibrosis induced by unilateral ureteral obstruction.