Optical properties of biological tissue are key parameters of optical imaging, and also provide useful information of the tissues under different physiological conditions. The optical attenuation coefficient (OAC) related to the optical properties can be calculated from optical coherence tomography(OCT) data. OCT has the advantages of high-resolution and fast imaging speed, and can image the tissues in vivo and in real-time. Due to the lack of blood perfusion, renal ischemia is accompanied by changes in microstructure of the kidney, which the OAC is sensitive to. We applied OCT to detect the OAC variation during ischemia-reperfusion process of rabbit kidney, and further estimated the ischemiareperfusion (I/R) injury. In order to study the temporal relationship between I/R injury and ischemia, 12 New Zealand rabbits were divided averagely into 4 groups (ischemia 30/60/90/120 min group). The kidneys were observed in vivo using a spectral domain OCT (SD-OCT) which light source centered at 900 nm. Three-dimensional OCT images of the kidney were obtained before the occlusion of renal artery and several time points after the blood reperfusion. The OAC were obtained by exponential fitting of OCT A-lines. Mapping attenuation coefficient (MAC) of each 3D OCT data set was performed to get the attenuation coefficient distribution in the kidney. The OAC curve with reperfusion time showed that the OAC was sensitive to ischemia and helpful for the estimation of ischemia-reperfusion injury. The distribution of attenuation coefficient in MAC image could reflect the local status of kidney.
Renal artery occlusion is an unavoidable process during operations such as nephrectomy, carcinoma resection, kidney transplantation and so on. For minimizing the kidney injury, the optimal renal ischemia time was experimentally investigated. Optical coherence tomography (OCT) is a high resolution imaging modality can non-invasively image biotissue in vivo and in real time. In order to study the relationship between tubular injury and the renal ischemia time, OCT images of Wistar rat kidneys endured various ischemia time were obtained throughout the whole ischemia-reperfusion procedure. The tubular density and the average diameter of uriniferous tubules were considered as biomarker of kidney activity, and the quantitative results well described the degree of kidney injury.