Qian Chunqi, Yu Xin, Pothayee Nikorn, Dodd Stephen, Bouraoud Nadia, Star Robert, Bennett Kevin, Koretsky Alan
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland;
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland; High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, Tubingen, Germany.
Am J Physiol Renal Physiol. 2014 Nov 15;307(10):F1162-8. doi: 10.1152/ajprenal.00326.2014. Epub 2014 Sep 3.
The local sensitivity of MRI can be improved with small MR detectors placed close to regions of interest. However, to maintain such sensitivity advantage, local detectors normally need to communicate with the external amplifier through cable connections, which prevent the use of local detectors as implantable devices. Recently, an integrated wireless amplifier was developed that can efficiently amplify and broadcast locally detected signals, so that the local sensitivity was enhanced without the need for cable connections. This integrated detector enabled the live imaging of individual glomeruli using negative contrast introduced by cationized ferritin, and the live imaging of renal tubules using positive contrast introduced by gadopentetate dimeglumine. Here, we utilized the high blood flow to image individual glomeruli as hyperintense regions without any contrast agent. These hyperintense regions were identified for pixels with signal intensities higher than the local average. Addition of Mn(2+) allowed the simultaneous detection of both glomeruli and renal tubules: Mn(2+) was primarily reabsorbed by renal tubules, which would be distinguished from glomeruli due to higher enhancement in T1-weighted MRI. Dynamic studies of Mn(2+) absorption confirmed the differential absorption affinity of glomeruli and renal tubules, potentially enabling the in vivo observation of nephron function.
通过将小型磁共振探测器放置在感兴趣区域附近，可以提高磁共振成像（MRI）的局部灵敏度。然而，为了保持这种灵敏度优势，局部探测器通常需要通过电缆连接与外部放大器通信，这使得局部探测器无法用作可植入设备。最近，开发了一种集成无线放大器，它可以有效地放大并广播局部检测到的信号，从而在无需电缆连接的情况下提高了局部灵敏度。这种集成探测器能够利用阳离子化铁蛋白引入的负性对比剂对单个肾小球进行实时成像，并利用钆喷酸葡胺引入的正性对比剂对肾小管进行实时成像。在此，我们利用高血流量，在不使用任何对比剂的情况下将单个肾小球成像为高强度区域。这些高强度区域是针对信号强度高于局部平均值的像素识别出来的。添加锰离子（Mn(2+)）能够同时检测肾小球和肾小管：Mn(2+)主要被肾小管重吸收，在T1加权MRI中，由于增强程度更高，肾小管将与肾小球区分开来。对Mn(2+)吸收的动态研究证实了肾小球和肾小管的不同吸收亲和力，这有可能实现对肾单位功能的体内观察。
