Using an ultrasound system for imaging allows as to investigate blood flow velocity parameters. By measuring the blood flow close to the partition, we are able to detect narrowing in the vessel.
Abstract
Using an ultrasound system for imaging allows as to investigate blood flow velocity parameters. By measuring the blood flow close to the partition, we are able to detect narrowing in the vessel. Paralleling the partition flow to the one in the center, allows us to discover pathological problems.
In order to measure the blood flow we used Doppler Effect of the Ultrasound. We imitated the vessel by using latex pipe in a flow plant.
Evaluating the pulse cycle
The classical parameters for blood flow are the PI & RI.
The pulsatility index (PI) is a measure for the oscillatory energy in the flow-velocity waveform. PI evaluates the pulse-wave damping along the vessel. The wider the vessel, the bigger is the PI.
The resistance index (RI) is a measure of circulatory resistance beyond the measurement point. A stenosis will cause to reduction in the blood flow and increase the resistance of the vessel.
Flow cycle and Jump Rate
The problem
The ultrasound results are the real time measurements. Therefore they are sensitive to noise which is hard to remove.
We confronted with few kinds of noises : the noise which the Synergy system adds, the noise which caused by the non-homogenic liquid and the environmental noise.
The ultrasound image
The solution
The noise, which added by the Synergy system, was detected as maximum amplitude pixels (higher than 250) and then removed.
High frequency noise was removed and smoothed by adjustable (the bandwidth is correlated to the chosen number of cycles) Low Pass Filter (LPF). By discovering the envelope of the wave we decided where there is unlikely to find the circulation cycle. We assumed that in this area there is not any information about flow distribution, but noise, and then we removed this noise from all image.
The image after noise removal
In order to calculate the PI, RI and Jump Rate parameters we had to find a relative line, which is the Synergy Zero Velocity Line.
Conclusion
The Jump Rate parameter in the middle of the pipe is higher then near the connections in the edges.
We did not get any absolute correlation about Jump Rate changes along the width of the pipe.
Many more measurements are needed in order to verify our results.
The tools
The project was implemented using the 5.2 Matlab for PC, Ultrasound device – SYNERGY and experimental system that simulates pulsating arterial blood flow.
Acknowledgment
We would like to thank Prof. Dan Adam for guiding us through the project. We would also like to thank the staff of the Department of Biomedical Engineering : Amit, Ran and Ram and to the Physiological Signal Processing Laboratory staff, especially to Johanan Erez.