Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.
Pritzker School of Medicine, University of Chicago, Chicago, Illinois, USA.
Am J Nephrol. 2020;51(12):966-974. doi: 10.1159/000512854. Epub 2021 Jan 28.
The estimated glomerular filtration rate (eGFR) is frequently used to monitor progression of kidney disease. Multiple values have to be obtained, sometimes over years to determine the rate of decline in kidney function. Recent data suggest that functional MRI (fMRI) methods may be able to predict loss of eGFR. In a prior study, baseline data with multi-parametric MRI in individuals with diabetes and moderate CKD was reported. This report extends our prior observations in order to evaluate the temporal variability of the fMRI measurements over 36 months and their association with annual change in eGFR.
Twenty-four subjects with moderate CKD completed 3 sets of MRI scans over a 36-month period. Blood oxygenation level-dependent (BOLD), arterial spin labeling perfusion, and diffusion MRI images were acquired using a 3 T scanner. Coefficients of variation was used to evaluate variability between subjects at each time point and temporal variability within each subject. We have conducted mixed effects models to examine the trajectory change in GFR over time using time and MRI variables as fixed effects and baseline intercept as random effect. Associations of MRI image markers with annual change in eGFR were evaluated.
Multi-parametric functional renal MRI techniques in individuals with moderate CKD showed higher temporal variability in R2* of medulla compared to healthy individuals. This was consistent with the significant lower R2* in medulla observed at 36 months compared to baseline values. The results of linear mixed model showing that R2*_Medulla was the only predictor associated with change in eGFR over time. Furthermore, a significant association of medullary R2* with annual loss of eGFR was observed at all the 3 time points.
The lower R2* values and the higher temporal variability in the renal medulla over time suggest the ability to monitor progressive CKD. These were confirmed by the fact that reduced medullary R2* was associated with higher annual loss in eGFR. These data collectively emphasize the need for inclusion of medulla in the analysis of renal BOLD MRI studies.
估算肾小球滤过率（eGFR）常用于监测肾脏疾病的进展。为了确定肾功能下降的速度，有时需要多年来多次获得该值。最近的数据表明，功能磁共振成像（fMRI）方法可能能够预测 eGFR 的损失。在之前的一项研究中，报告了糖尿病和中度 CKD 患者的基线多参数 MRI 数据。本报告扩展了我们之前的观察结果，以评估 fMRI 测量值在 36 个月内的时间变异性及其与 eGFR 年变化的相关性。
24 名中度 CKD 患者在 36 个月内完成了 3 组 MRI 扫描。使用 3T 扫描仪采集血氧水平依赖（BOLD）、动脉自旋标记灌注和弥散 MRI 图像。使用变异系数来评估每个时间点的受试者之间的变异性和每个受试者内的时间变异性。我们使用混合效应模型，以时间和 MRI 变量作为固定效应，以基线截距作为随机效应，来检查 GFR 随时间的轨迹变化。评估 MRI 图像标志物与 eGFR 年变化的相关性。
在中度 CKD 患者中，多参数功能性肾脏 MRI 技术显示肾髓质 R2的时间变异性高于健康个体。这与 36 个月时观察到的肾髓质 R2明显低于基线值的情况一致。线性混合模型的结果表明，R2*_Medulla 是唯一与 eGFR 随时间变化相关的预测因子。此外，在所有 3 个时间点均观察到肾髓质 R2*与 eGFR 年损失的显著相关性。
随着时间的推移，肾髓质的 R2值降低和时间变异性增加表明能够监测进行性 CKD。这一事实得到了证实，即降低的肾髓质 R2与更高的 eGFR 年损失相关。这些数据共同强调了在肾脏 BOLD MRI 研究中分析肾髓质的必要性。
