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Development of a Wrist PPG Probe for the Measurement of Radial Artery Diameter

Keikhosravi, Adib | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43105 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zahedi, Edmond
  7. Abstract:
  8. Inability of endothelial cells in responding to metabolic needs (endothelial dysfunction,) is a sign of heart diseases like atherosclerosis and vascular stenosis. Recently, a new method using finger PPG signal has been proposed to determine endothelial function in response to reactive hypertension (RH.) PPG-based endothelial function assessment results are not fully correlated with ultrasound FMD tests, and this is because of some auto-regulation phenomena in the fingertip. It is expected that such problems will not exist in larger arteries, like the radial artery. The goal of this project is to acquire the PPG signal from the radial artery as it is proportional to blood volume changes in this artery. In this research, first using Monte Carlo estimation method, light-tissue interaction patterns for radial artery were extracted, and optimum distances between LEDs and photodiodes, and arrangement of them were designed. The designed probes were then assembled, and recorded signals were processed to evaluate their modulation with radial artery blood volume changes. Because of providing high modulation ratios as exhibited in simulations, two wavelengths of 400 nm and 940 nm were selected. For each of these wavelengths the arrangement of LED and photodiodes were designed based on simulations and wrist anatomy. The 400 nm probe, tested first, acquired signals that did not trace the blood volume changes, probably because of high absorption and low sensitivity at this wavelength. The 940 nm probe was successful to record signals highly correlated with finger PPG. The AC parts of wrist PPG and finger PPG were 94% correlated, and DC parts 84% correlated (whole of signals show more than 89% correlation.). Finaly an FMD test was done for monitoring autoregulation in fingertip. Results showed that autoregulation causes more dilation in fingertip capilatries than radial artery.
    Inability of endothelial cells in responding to metabolic needs (endothelial dysfunction,) is a sign of heart diseases like atherosclerosis and vascular stenosis. Recently, a new method using finger PPG signal has been proposed to determine endothelial function in response to reactive hypertension (RH.) PPG-based endothelial function assessment results are not fully correlated with ultrasound FMD tests, and this is because of some auto-regulation phenomena in the fingertip. It is expected that such problems will not exist in larger arteries, like the radial artery. The goal of this project is to acquire the PPG signal from the radial artery as it is proportional to blood volume changes in this artery. In this research, first using Monte Carlo estimation method, light-tissue interaction patterns for radial artery were extracted, and optimum distances between LEDs and photodiodes, and arrangement of them were designed. The designed probes were then assembled, and recorded signals were processed to evaluate their modulation with radial artery blood volume changes. Because of providing high modulation ratios as exhibited in simulations, two wavelengths of 400 nm and 940 nm were selected. For each of these wavelengths the arrangement of LED and photodiodes were designed based on simulations and wrist anatomy. The 400 nm probe, tested first, acquired signals that did not trace the blood volume changes, probably because of high absorption and low sensitivity at this wavelength. The 940 nm probe was successful to record signals highly correlated with finger PPG. The AC parts of wrist PPG and finger PPG were 94% correlated, and DC parts 84% correlated (whole of signals show more than 89% correlation.). Finaly an FMD test was done for monitoring autoregulation in fingertip. Results showed that autoregulation causes more dilation in fingertip capilatries than radial artery
  9. Keywords:
  10. Flow Mediated Dilation ; Wrist Photoplethysmography Probe ; Radial Artery Diameter Changes ; Monte Carlo Optical Simulation

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