Blood-flow MRI of Non-human Primate (Baboon) Retina
نویسندگان
چکیده
INTRODUCTION Advances in MRI technologies have made it possible to achieve multilayer resolution of the thin retina of only 276 micron thick (1). In rodent and cat retinas, three to seven MRI-resolved anatomical layers have been reported depending on whether contrast agent was used (1-3). Contrast-enhanced MRI following intravenously injection of Gd-DTPA revealed two unique (retinal and choroidal) vascular layers and the avascular photoreceptor layer and segments in between (1). More recently, blood flow (BF) MRI recorded quantitative perfusion in the whole retina in rodents (4) to be about 8 times higher than cerebral BF, consistent with the microsphere technique (8). Blood flow contrast in normal human retinas has also been presented in a conference abstract in 2000 (5). Abnormal BF in the retina has been widely implicated in many retinal diseases, including diabetic retinopathy, glaucoma, and retinal ischemia, and thus the ability to reliably image BF in the retina could have many important applications. In this study, we implemented a pseudo-continuous ASL (6) with echo-planar image (EPI) and balanced steady state free precession (bSSFP) acquisition to improve ASL contrast on clinical scanner and explored BF MRI of the retina in anesthetized/paralyzed non-human primate (baboon) as a first step toward evaluating potential human applications. Anesthetized baboons were used to exclude movement artifacts, allowing us to focus on evaluating hardware feasibility and imaging parameters for high-resolution quantitative BF imaging of the retina.
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