Feasibility of Specular Reflection Imaging for Extraction of Neck Vessel Pressure Waveforms

Figures

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  FIGURE 1. Three types of reflection from the turbid tissues. Diffuse reflection (A) and specular (Fresnel) reflection from smooth surface (B) and rough surface (C).

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  FIGURE 2. Acquisition setup.

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  FIGURE 3. Image processing flow.

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  FIGURE 4. Neighbors to the central region at position i,j, with i representing rows and j representing columns.

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  FIGURE 5. Correlation of each local SRVI (red (A), green (B), and blue (C) channels, respectively) to the global SRVI extracted from the ROI (value of Pearson correlation coefficient shown using coloring), overlaid as a transparent map on the first video frame.

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  FIGURE 6. (A) The first region generating local SRVI signals with high internal correlation, with the colour bar indicating correlation of the local SRVIs to the average SRVI in that region, (B) the second region generating local SRVI signals with high internal correlation, with the colour bar indicating correlation of the local SRVIs to the average SRVI in that region, and (C) the SRVI signals from the first and second regions plotted in the time domain, and analyzed using cross-correlation (as acquired, and with the second signal inverted).

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  FIGURE 7. Framing and region of interest (red rectangle) that excludes the mask.

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  FIGURE 8. Local correlation analysis, with the color bar indicating the average Pearson correlation coefficient of each central local SRVI to its 8 neighbors.

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  FIGURE 9. Comparison of ECG (blue) and SRVI signals (carotid artery signal in red and JV pulse signal in yellow). ECG landmarks are P-waves representing maximal atrial depolarization (squares), R-peaks representing maximal ventricular depolarization (circles) and T-wave representing maximal ventricular repolarization (triangles). The carotid artery SRVI landmarks are systolic peaks (circles) and estimated diastolic peaks (triangles). The JV pulse SRVI landmarks are a-waves representing atrial contraction (circles) and c-waves representing right ventricular contraction (triangles).