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Simulating Light Propagation and Photoplethysmography Signal Generation over the Radial Artery

Hosseini, Soheil | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42553 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zahedi, Edmond
  7. Abstract:
  8. Measuring the human brachial arterial diameter has significant applications in medical research. This is conventionally carried out using ultrasonography which is costly and operator-skill dependent. The objective of this project is to come up with substitute solutions based on optical measurement. Reflectance photoplethysmography (PPG) over the radial artery has been considered to this end. Monte Carlo method has been employed to simulate light propagation in the wrist area, along with a model comprising tissue, artery and bone, made of simple solid geometries. Functions of optical parameters such as refractive index, absorption coefficient, scattering coefficient and anisotropy factor have been illustrated in a graphic fashion. A framework has been created that allows for conducting new experiments and an efficient way of presenting the results. In this project, a sequence of 13 experiments have been performed to highlight the effects of optical parameters, systole and diastole, size and position of artery and bone, and consequently light patterns on skin and volume fluxes in the transverse and sagittal planes have been compared. Light amplitude maps (λ=815nm) confirm the well-known exponential decay with distance. With the light source and detector positioned on opposite sides of the radial artery and then changing the diameter, light amplitude has been recorded through simulation and the results have been evaluated using existing experimental reflectance PPG and arterial diameter synchronous signals. AC light amplitude shows a hysteresis relation to diameter contrary to simulation results, implying that dynamic modeling should be considered. Also minimal arterial penetration has been observed for detected light. Finally, a procedure has been introduced that allows for accurate anatomical models to be used in simulation
  9. Keywords:
  10. Monte Carlo Simulation ; Absorption ; Scattering ; Reflectance Photoplethysmography ; Radial Arterial Diameter ; Light-Tissue Interaction ; Anisotropy Factor

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