Swept-Source OCT: A Promising Imaging Modality for Kidney Doner Viability
Q. Li, M. L. Onozaro, P. M. Andrews, C. Chen, A. Paek, R. Naphas, S. Yuan, A. Cable, and Y. Chen
Above: Volume historgram of the distribution of blood vessel diameters. Below: Illustration of the boundary (black), skeleton (grey), and select radii (red) for a tubular struture of intrest.
Optical Coherence Tomography (OCT), a noninvasive, non-contact, high-resolution imaging modality has recently been employed for real-time, ex vivo studies of the human kidney. With an imaging depth up to 800 μm in renal tissue and the ability to scan the entire organ quickly, OCT is capable of providing a global in situ assessment of renal blood vessels, tubules, and glomeruli. Such information on tubular morphology has been linked to kidney donor viability, making OCT a promising candidate for clinical renal evaluation prior to transplant.
Recently a collaborative group of researchers from the University of Maryland and Georgetown University used a Thorlabs Swept Source Optical Coherence Tomography system (1325 nm central wavelength, 16 kHz scan rate) to obtain cross-sectional images of a human kidney in vitro and then used that information to determine the diameters of blood vessels automatically with a custom image processing algorithm. During the experiment, cross-sectional 3 mm x 3 mm x 2.25 mm images of the kidney (512 x 512 x 512 pixels) were obtained. Since the various tubular structures within the kidney (i.e., blood vessels, tubules, and glomeruli) exhibit different backscattering intensities, an automated image processing method was used to isolate the different regions of interest (ROI). The boundary and skeleton are then determined for each ROI, thereby enabling the calculation of the diameters of each luminal position based on the shortest skeletal-boundary distances (refer to Fig. 1).
Figure 2 shows cross-sectional OCT images of the human kidney obtained in the XY (frame a), XZ (frame b), and YZ (frame c) planes as well as the composite 3D view (frame d). Although the various kidney vascular networks are distinguishable in all three cross-sectional images, segmentation was used to isolate the renal blood vessels to determine their luminal diameters; then 3D visualization software was used to reconstruct the blood vessel images (see frames e, f, and g).
In this study, Li et al. show that OCT can be used for high-speed, real-time 3D visualization and volumetric rendering of dimensional changes in renal blood vessels and other tubular structures. Due to the high acquisition rate, the entire kidney can be evaluated within a short timeframe, making this method a viable option for kidney imaging and evaluation of physiological functions within a clinical setting.
OCT images of renal blood vessels were obtained in the (a) XY, (b) XZ, and (c) YZ planes and used to construct the composit #D image shown in frame d. (e) 3D volumetric image of the segmented blood vessels. (f) Measured and color-coded 3D image of the renal diameters.
All procedures were approved by the Institutional Review Board (IRB) at both the University of Maryland and Georgetown University.
Q. Li, M. L. Onozaro, P. M. Andrews, C. Chen, A. Paek, R. Naphas, S. Yuan, A. Cable, and Y. Chen. Optics Express. 17, 16000 (2009).