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M. Shahidi, M. Mori, J. M. Wanek; A Method for Three-Dimensional Chorioretinal Oxygen Tension Imaging. Invest. Ophthalmol. Vis. Sci. 2007;48(13):125.
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Oxygen plays an important role in the maintenance of normal retinal function. Derangements in retinal oxygenation have been implicated in the development of many retinal diseases. Technologies that allow direct assessment of retinal oxygenation are needed to provide better understanding of disease pathophysiology and to investigate the role of oxygen in the development of disease-related retinal pathologies. A system based on optical section retinal imaging was developed that allowed three-dimensional mapping of oxygen tension in the chorioretinal vasculatures.
Three-dimensional mapping of chorioretinal oxygen tension was performed in rat eyes. A laser beam was projected at an oblique angle on the retina following intravenous injection of an oxygen sensitive molecular probe to generate an optical section phosphorescence image in the YZ plane of the retina. Since the incident laser beam was not coaxial with the viewing axis, chorioretinal vasculatures appeared laterally displaced according to their depth location on the phosphorescence optical section image. By scanning the laser beam in small horizontal steps across a retinal area, a series of optical section images from spatially adjacent locations was acquired. An automated software algorithm segmented the phosphorescence optical section images and combined the segments from the same retinal depths to reconstruct depth-displaced images in the XY retinal planes. Oxygen tension in the chorioretinal vasculatures was mapped based on phosphorescence lifetime measurements.
A composite of phosphorescence optical section images acquired in a laser scan displayed depth-resolved oxygenation in the chorioretinal vasculatures. By segmenting and combining phosphorescence optical section images, a set of phase-delayed intensity images of the vascular layers was constructed. Since the phosphorescence is quenched by oxygen, low and high oxygenation was visualized as high and low intensity values on the images, respectively. The phase-delayed images were analyzed to generate three-dimensional oxygen tension maps that allowed differential imaging of oxygenation in the retinal and chorioidal vasculatures. The chorioretinal oxygen tension maps allowed quantitative measurement of oxygen tension in the retinal arteries, veins, capillaries and in the choroid.
A method was developed for three-dimensional mapping of oxygen tension in the chorioretinal vasculatures that has potential to provide better understanding of retinal oxygenation in health and disease.
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