Non-Invasive Blood Flow Speed Measurement Using Optics

Figures

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  Figure 1. Experimental Setup. The laser light illuminates the tissue phantom surface at a 45-degree angle and the scattered diffused light is collected through the reflection probe fiber bundle which is coupled to a photoreceiver. The glass tube that emulates a blood vessel is embedded in the tissue phantom 5 mm below the surface.

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  Figure 2. (a) Measured E-field correlation function (g1) versus flow speed of whole blood for a tube diameter of 1.68 mm. (b) By taking the inverse of the correlation time at the first inflection point in (a), marked using ‘X’, the decorrelation rate (1/TF) is plotted versus the flow speed. The scattered data set with error bars represents the 95% confidence interval over 25 measurements, each for a duration of 1 s. The dashed line is a linear fit of the measured data.

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  Figure 3. (a) Measured E-field correlation function (g1) versus flow speed of whole blood for a tube diameter of 1.14 mm. (b) By taking the inverse of the correlation time at the first inflection point in (a), marked using ‘*’, the decorrelation rate (1/TF) is plotted versus the flow speed. The scattered data set with error bars represents the 95% confidence interval over 25 measurements, each for a duration of 1 s. The dashed line is a linear fit of the measured data.

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  Figure 4. (a) Measured E-field correlation function (g1) versus flow speed of whole blood for a tube diameter of 0.93 mm. (b) By taking the inverse of the correlation time at the first inflection point in (a), marked using ‘△’, the decorrelation rate (1/TF) is plotted versus the flow speed. The scattered data set with error bars represents the 95% confidence interval over 25 measurements, each for a duration of 1 s. The dashed line is a linear fit of the measured data.

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  Figure 5. Combined decorrelation rate (1/TF) versus blood flow speed plot for different tube ID. The scattered data set with the error bar represents the 95% confidence interval over 25 measurements, each for a duration of 1 s. The line plots are linear fits of the measured data. The fact that plots for different tube IDs collapse into one single line demonstrates the existence of a simple relation between the decorrelation rate and the blood speed, and the relation is independent of the tube diameter.

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  Figure 6. Illustration of the elementary scattering volume for Equation (3).

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  Figure 7. Geometry used for theoretical calculation. The circle represents the cross section of blood vessel with parameters: Din, W1, k1, μain, μs′in; The area outside the circle represents the static scattering media, i.e., tissue with parameters Dout, W0, k0, μaout, μs′out. We adopt cylindrical coordinates and define the center of the vessel as the origin.

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  Figure 8. Comparison between theoretical calculations (from Equation (17) and experimentally measured decorrelation rates under different blood flow speeds and tube diameters. The scattered data set with the error bar represents the 95% confidence interval over 25 measurements. Each measurement took 1 s. The following parameters are used in the calculations: n=1.36, μs′in=1600m−1 and μain=1000m−1 for deoxygenated blood [41,42,43,44].