Tasbihi Ehsan, Gladytz Thomas, Millward Jason M, Cantow Kathleen, Seeliger Erdmann, Niendorf Thoralf
Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility (B.U.F.F.), Berlin, Germany.
Charité-Universitätsmedizin Berlin, Berlin, Germany.
Acta Physiol (Oxf). 2025 Sep;241(9):e70095. doi: 10.1111/apha.70095.
The renal tubular volume fraction (TVF) fluctuates under physiological conditions, and is altered in several renal diseases. Tools that enable noninvasive assessment of TVF are currently lacking. Magnetic Resonance (MR) TVF cartography is a novel approach for unraveling renal (patho-)physiology. Here, we employ MR-TVF cartography to monitor changes in response to the diuretic furosemide, and examine its role for the interpretation of renal oxygenation assessed by mapping the MRI relaxation time T*. We hypothesize that furosemide increases TVF.
In anesthetized rats (n = 7) the MRI relaxation times T, T*, T' and kidney size were obtained before/following an i.v. bolus of furosemide using a 9.4 Tesla MRI scanner. Spectral analysis of the T signal decay was performed to estimate the number of T components in renal tissue. TVF cartographies were calculated using voxel-wise bi-exponential fit of the T decay. Near Infrared Spectroscopy (NIRS, n = 9) was used to assess the total hemoglobin concentration (HbT) as a surrogate of renal blood volume.
Furosemide induced changes in renal MRI and NIRS parameters relative to baseline: TVF = 31.1%, TVF = 30.7%, T = 13.0% and T = 20.6%. HbT was reduced by 2.7%. HbT declined by 8.6%. Kidney size showed a modest increase of 2.9%. T* and T´ rose by 20.5% and 20.2%. T* and T´ remained unchanged. T* and TVF were strongly correlated in the outer medulla and moderately in the cortex.
MR-TVF cartography is highly relevant for elucidating mechanisms of renal (patho-)physiology, including the role of renal oxygenation assessed by MRI mapping of renal T*.
肾小管体积分数（TVF）在生理条件下会波动，且在多种肾脏疾病中会发生改变。目前缺乏能够非侵入性评估TVF的工具。磁共振（MR）TVF成像术是一种揭示肾脏（病理）生理学的新方法。在此，我们采用MR-TVF成像术来监测对利尿剂呋塞米的反应变化，并通过绘制MRI弛豫时间T*来评估肾脏氧合作用，研究其在这一过程中的作用。我们假设呋塞米会增加TVF。
使用9.4特斯拉MRI扫描仪，在麻醉大鼠（n = 7）静脉注射呋塞米推注剂之前/之后，获取MRI弛豫时间T、T*、T'和肾脏大小。对T信号衰减进行光谱分析，以估计肾组织中T成分的数量。使用T衰减的体素双指数拟合计算TVF成像图。近红外光谱法（NIRS，n = 9）用于评估总血红蛋白浓度（HbT），作为肾血容量的替代指标。
与基线相比，呋塞米引起肾脏MRI和NIRS参数变化：TVF = 31.1%，TVF = 30.7%，T = 13.0%，T = 20.6%。HbT降低了2.7%。HbT下降了8.6%。肾脏大小适度增加了2.9%。T和T´分别上升了20.5%和20.2%。T和T´保持不变。在外髓质中，T*与TVF高度相关，在皮质中呈中度相关。
MR-TVF成像术对于阐明肾脏（病理）生理学机制高度相关，包括通过肾脏T*的MRI映射评估的肾脏氧合作用的作用。
