Measurement of liquid velocity and pressure by laser doppler technology

number: 
2227
إنجليزية
Degree: 
Author: 
Abeer Hussein Ali
Supervisor: 
Dr. Anwaar A. Al-Dergazly
year: 
2009
Abstract:

. Laser Doppler flowmetry uses Doppler effect in the optical domain to measure velocities of fluids in closed tubes. This technique is useful in the field of biomedical applications since it offers a rapid, direct, and potentially high resolution method of determining blood velocity. The purpose of this thesis is to find a simple and non invasive method to measure the blood velocity and blood pressure by means of Doppler effect technique. The design and construction of a laser Doppler flowmetry is reported. The measurements are obtained by detecting the interference signal using a photo-resistor. A MATLAB 7 program is written to obtain the power spectrum density of the detected signal which contains the needed information about blood velocity and blood pressure. Different types of lasers are used to demonstrate the operation of the designed system: He-Ne laser, second harmonic generation Nd:YAG laser and Nd:YVO4 laser. The measurements of the designed laser Doppler flowmetry are first used in the field of industry. A tube with 8mm diameter and 19cm long is used. The measurements are taken for pure water and repeated with different planktons. The results are used as a guideline to refine the proposed design for medical application. Then the measurements are turned to medical measurements by applying the same technique to measure the blood flow and blood pressure in the left hand vein and fingertip capillaries. The measured velocities of water seeded with different planktons with He-Ne laser are in good match with the theoretical measurements. The minimum blood pressure obtained in the fingertip is 35mmHg and the maximum is 67mmHg. While the minimum pressure obtained in the vein is 36mmHg and the maximum is 66mmHg.