The retina is approximately 300 mu m thick and is metabolically very active. With limited energy reserve, it depends solely on a continuous supply of oxygen and nutrients to maintain its functional and structural integrity. The retina is nourished by two blood supplies, namely, the retinal and choroidal circulation, that feed the inner (i.e., ganglion cells) and the outer (i.e., photoreceptors) retina, respectively. Oxygen transport into the highly structured retinal cell layers relies heavily on diffusion. As such, the oxygen tension midway between the inner and outer retina is close to hypoxic level under normal conditions and, thus, the retina is very susceptible to ischemic injury. Oxygenation and perfusion deficits have been implicated in numerous retinal diseases. A non-invasive method to map changes in retinal and choroidal oxygenation and perfusion would be valuable. Non-invasive magnetic resonance imaging (MRI) has been widely used for investigating anatomy, physiology and function in both animals and humans. While tissue oxygenation and perfusion imaging is routine for studying brain functions, its application to the eye is technically difficult due to the thin retina and its proximity to the air-filled cranial cavity. Recent data from our lab demonstrate that blood-oxygenation-level-dependent (BOLD) functional MRI can dynamically map visual-evoked changes in oxygenation in the retina. The main goals of this proposal are: 1) to develop and validate high-resolution (58x58x1000 mu m3) MRI modalities to map choroidal and retinal oxygenation and perfusion in the retina, and 2) to investigate the visual-evoked layer-specific responses to differential activations of photoreceptor versus ganglion cell activity by measuring changes in the choroidal versus retinal oxygenation and perfusion. Studies will be performed on cats using a 4.7 Tesla scanner.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY014211-10
Application #
8111840
Study Section
Biomedical Imaging Technology Study Section (BMIT)
Program Officer
Shen, Grace L
Project Start
2008-08-01
Project End
2013-07-31
Budget Start
2011-08-01
Budget End
2013-07-31
Support Year
10
Fiscal Year
2011
Total Cost
$352,836
Indirect Cost
Name
University of Texas Health Science Center San Antonio
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78229
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Muir, Eric R; Chandra, Saurav B; De La Garza, Bryan H et al. (2015) Layer-Specific Manganese-Enhanced MRI of the Diabetic Rat Retina in Light and Dark Adaptation at 11.7 Tesla. Invest Ophthalmol Vis Sci 56:4006-12
Muir, Eric R; Cardenas, Damon; Huang, Shiliang et al. (2014) MRI under hyperbaric air and oxygen: effects on local magnetic field and relaxation times. Magn Reson Med 72:1176-81
Duong, Timothy Q (2014) Magnetic resonance imaging of the retina: from mice to men. Magn Reson Med 71:1526-30
Shih, Yen-Yu I; De La Garza, Bryan H; Huang, Shiliang et al. (2014) Comparison of retinal and cerebral blood flow between continuous arterial spin labeling MRI and fluorescent microsphere techniques. J Magn Reson Imaging 40:609-15
Emeterio Nateras, Oscar San; Harrison, Joseph M; Muir, Eric R et al. (2014) Choroidal blood flow decreases with age: an MRI study. Curr Eye Res 39:1059-67
Muir, Eric R; Zhang, Yi; San Emeterio Nateras, Oscar et al. (2013) Human vitreous: MR imaging of oxygen partial pressure. Radiology 266:905-11
Park, Sung-Hong; Wang, Danny J J; Duong, Timothy Q (2013) Balanced steady state free precession for arterial spin labeling MRI: Initial experience for blood flow mapping in human brain, retina, and kidney. Magn Reson Imaging 31:1044-50
Shih, Yen-Yu I; Wang, Lin; De La Garza, Bryan H et al. (2013) Quantitative retinal and choroidal blood flow during light, dark adaptation and flicker light stimulation in rats using fluorescent microspheres. Curr Eye Res 38:292-8
Li, Guang; Kiel, Jeffrey W; Cardenas, Damon P et al. (2013) Postocclusive reactive hyperemia occurs in the rat retinal circulation but not in the choroid. Invest Ophthalmol Vis Sci 54:5123-31

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