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Updated: May 6, 2026
Author Spotlight: Noninvasive Cerebral Blood Flow Determination in Human Functional Brain Region for Diagnosis of Neurological Disorders
Published on: May 31, 2024
Comparison of retinal and cerebral blood flow between continuous arterial spin labeling MRI and fluorescent
Yen-Yu I Shih1, Bryan H De La Garza, Shiliang Huang
1Departments of Neurology, Biomedical Research Imaging Center, and Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, USA; Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
Purpose:
To compare basal retinal and cerebral blood flow (BF) values using continuous arterial spin labeling (CASL) MRI and fluorescent microspheres.
Materials And Methods:
A total of 41 animals were used. BF was measured using an established microsphere technique (a mixture of 2.5 million 8 μm green and 0.5 million 10 μm blue fluorescent microspheres) and CASL MRI blood flow measurement in the rat retina and brain at 7 Tesla (T) and 11.7T, respectively.
Results:
Retinal BF by MRI was 1.18 ± 0.57 mL/g/min and choroidal BF was 8.14 ± 1.8 mL/g/min (n = 6). Microsphere retinal BF was 9.12 ± 2.8 μL/min per tissue and choroidal BF was 73.38 ± 44 μL/min per tissue (n = 18), corresponding to a retinal BF value of 1.22 ± 0.36 mL/g/min by means of a wet weight conversion. The wet-weight of the choroid could not be determined. To corroborate our findings, cerebral BF (CBF) by MRI was also analyzed. In the cerebral cortices, CBF was 0.91 ± 0.29 mL/g/min (n = 14) by CASL MRI and 1.09 ± 0.37 mL/g/min (n = 6) by microspheres. There were no significant differences found between MRI and microsphere blood flow in the retina and brain.
Conclusion:
BF values in the rat retina and cerebral cortex by MRI are in agreement with those obtained by the microsphere technique.
Insights
Continuous arterial spin labeling MRI and fluorescent microspheres provide comparable measurements for retinal and cerebral blood flow (BF) in rats. This validates MRI as a reliable method for assessing BF in these critical tissues.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Ophthalmology
Background:
- Accurate measurement of blood flow (BF) in the retina and brain is crucial for understanding physiological processes and disease states.
- Established methods like fluorescent microspheres offer high accuracy but are invasive.
- Non-invasive techniques are needed for routine assessment and longitudinal studies.
Purpose of the Study:
- To compare basal retinal and cerebral blood flow (BF) values obtained using continuous arterial spin labeling (CASL) Magnetic Resonance Imaging (MRI) with those measured by the gold-standard fluorescent microsphere technique.
- To validate CASL MRI as a non-invasive method for quantifying BF in the rat retina and brain.
Main Methods:
- Blood flow was measured in 41 animals using both fluorescent microspheres and CASL MRI.
- MRI measurements were performed at 7 Tesla (T) for the retina and 11.7T for the brain.
- Microsphere technique involved injecting a mixture of green and blue fluorescent microspheres.
Main Results:
- Retinal BF by MRI was 1.18 ± 0.57 mL/g/min, comparable to 1.22 ± 0.36 mL/g/min by microspheres (wet weight conversion).
- Cerebral BF (CBF) in the cortex was 0.91 ± 0.29 mL/g/min by MRI and 1.09 ± 0.37 mL/g/min by microspheres.
- No significant differences were observed between MRI and microsphere measurements for both retinal and cerebral BF.
Conclusions:
- CASL MRI provides reliable and comparable measurements of basal retinal and cerebral blood flow in rats.
- MRI offers a non-invasive alternative to the microsphere technique for BF assessment in these tissues.
- These findings support the use of CASL MRI in preclinical research for evaluating vascular function.
