| The Effect of Hypercarbia and Hyperoxia on the Total Blood Flow to the Retina as Assessed by Magnetic Resonance Imaging. | |
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MedLine Citation:
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PMID: 21447683 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Purpose: The feasibility of measuring total blood flow to the retina with Arterial Spin Labeling Magnetic Resonance Imaging (ASL-MRI) has been described previously. In the current study, we hypothesized that the reactivity the ASL-MRI detects at the human retina is dominated by the choroidal blood flow contribution and thus it may serve as a useful tool for quantitative assessment of the choroidal vascular reactivity. Methods: Prior to imaging, the intra-ocular pressure (IOP) was measured in the study eye of 9 clinically healthy subjects (4 males) while the subject performed the ventilatory protocol subsequently performed in the scanner. End-tidal CO(2) partial pressure (P(ET)CO(2)) was increased to target 45 mmHg, (baseline P(ET)CO(2) = 40 mmHg and baseline P(ET)O(2) = 100mmHg). P(ET)O(2) was then increased to target 300 mmHg, and 500 mmHg while keeping P(ET)CO(2) constant at 45mmHg. A background suppressed Pulsed-Continuous ASL sequence was used for blood flow imaging. Results: The measured total blood flow increased significantly from 1.55±0.17μL/mm2/min at the baseline to 1.96±0.18μL/mm2/min during hypercarbia. With increasing P(ET)O(2), the measured blood flow did not change significantly relative to the hypercarbia condition but remained significantly elevated relative to the baseline. There were no significant changes in systolic, diastolic or mean blood pressure, heart rate or IOP during all four breathing conditions. Conclusion: The lack of change in the ASL signal under hyperoxic conditions is consistent with that this non-invasive assessment technique is predominantly weighted by choroidal blood flow. Our results indicate that a CO(2) provocation challenge in combination with the ASL-MRI is a promising noninvasive approach to investigate choroidal vascular reactivity under normal and disease states. |
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Authors:
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Nasim Maleki; David C Alsop; Weiying Dai; Christopher Hudson; Jay S Han; Joe Fisher; David Mikulis |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-3-29 |
Journal Detail:
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Title: Investigative ophthalmology & visual science Volume: - ISSN: 1552-5783 ISO Abbreviation: - Publication Date: 2011 Mar |
Date Detail:
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Created Date: 2011-3-30 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7703701 Medline TA: Invest Ophthalmol Vis Sci Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Department of Psychiatry, McLean Hospital and Harvard Medical School, Boston, MA USA; |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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