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Theodore Smith, Yuehong Tong, Jennifer Acton, Amani A. Fawzi, Liang Gao, Tomasz S. Tkaczyk; Dynamic Hyperspectral Retinal Oximetry in a Human with the Image Mapping Spectrometer (IMS). Invest. Ophthalmol. Vis. Sci. 2012;53(14):2185.
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We present a hyperspectral retinal camera capable of real-time imaging of oxygen saturation dynamics, as demonstrated in a human experiment.
The Image Mapping Spectrometer (IMS) is a hyperspectral camera that simultaneously acquires full 48 channel hyperspectral cubes in the range 470 nm - 650 nm (spectral resolution ~ 3.6 nm) with a frame rate at 5.2 fps and spatial resolution 350×350 pixels (Gao et al, Opt Express, 2010). We coupled it to a standard fundus camera (Topcon TRC50X, Topcon Inc, Tokyo, Japan) and acquired a hyperspectral movie of the optic disc region in a healthy 22 y/o female with the illumination light of the camera (no flash). The absorption spectral signature of oxy-hemoglobin was extracted from the reflectance data and used to construct a relative oxygen saturation (ROS) map at each time point with known techniques (Khoobehi et al, IOVS, 2004).
The ROS maps fell in the normal ranges 0.05 - 0.2 found by Khoobehi et al in primates. Measurement on the largest arteriole showed marked pulsatile behavior (Fig 1, selected frames) consistent with the subject’s pulse, although the frame rate was not fast enough to catch every pulse.
We report the first sub-second resolution dynamic hyperspectral retinal oximetry in a human. An even faster frame rate would be better for capturing arterial transients. This is a promising technique to investigate the normal retinal circulation and retinal vascular disease.
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