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Measurement of Retinal Blood Flow Using Fluorescently Labeled Red Blood Cells.

Kornfield TE, Newman EA - eNeuro (2015 Mar-Apr)

Bottom Line: The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs).Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels.We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455.

ABSTRACT

Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.

No MeSH data available.


Related in: MedlinePlus

RBC velocity profiles across the width of blood vessels using diagonal line scans. A, B, Velocity was determined at many points across the width of an arteriole (A) and a venule (B) by measuring the angle of fRBC streaks along the diagonal line scan. Velocity measurements were fit with a second-order polynomial (solid lines). C, Parabolic fits of RBC velocities for individual arterioles (red) and venules (blue).
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Figure 7: RBC velocity profiles across the width of blood vessels using diagonal line scans. A, B, Velocity was determined at many points across the width of an arteriole (A) and a venule (B) by measuring the angle of fRBC streaks along the diagonal line scan. Velocity measurements were fit with a second-order polynomial (solid lines). C, Parabolic fits of RBC velocities for individual arterioles (red) and venules (blue).

Mentions: A second method was used to measure velocity profiles in single trials. High-frequency line scans oriented diagonally across a vessel (Fig. 1E) captured the velocity of individual fRBCs across the vessel width. Velocity was computed at 10 positions along the line. The advantage of this method is that the full velocity profile can be determined from a single line scan trial. Examples of velocity profiles from an arteriole and venule are shown in Figure 7, A and B. Fitting the data from each trial with a quadratic equation yielded an average maximum velocity of 23.7 mm/s for arterioles and 11.9 mm/s for venules (Fig. 7C).


Measurement of Retinal Blood Flow Using Fluorescently Labeled Red Blood Cells.

Kornfield TE, Newman EA - eNeuro (2015 Mar-Apr)

RBC velocity profiles across the width of blood vessels using diagonal line scans. A, B, Velocity was determined at many points across the width of an arteriole (A) and a venule (B) by measuring the angle of fRBC streaks along the diagonal line scan. Velocity measurements were fit with a second-order polynomial (solid lines). C, Parabolic fits of RBC velocities for individual arterioles (red) and venules (blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465795&req=5

Figure 7: RBC velocity profiles across the width of blood vessels using diagonal line scans. A, B, Velocity was determined at many points across the width of an arteriole (A) and a venule (B) by measuring the angle of fRBC streaks along the diagonal line scan. Velocity measurements were fit with a second-order polynomial (solid lines). C, Parabolic fits of RBC velocities for individual arterioles (red) and venules (blue).
Mentions: A second method was used to measure velocity profiles in single trials. High-frequency line scans oriented diagonally across a vessel (Fig. 1E) captured the velocity of individual fRBCs across the vessel width. Velocity was computed at 10 positions along the line. The advantage of this method is that the full velocity profile can be determined from a single line scan trial. Examples of velocity profiles from an arteriole and venule are shown in Figure 7, A and B. Fitting the data from each trial with a quadratic equation yielded an average maximum velocity of 23.7 mm/s for arterioles and 11.9 mm/s for venules (Fig. 7C).

Bottom Line: The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs).Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels.We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455.

ABSTRACT

Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.

No MeSH data available.


Related in: MedlinePlus