THE APPLICATION OF ECHO-TRACKING METHODS TO ENDOTHELIUM-DEPENDENT VASOREACTIVITY AND ARTERIAL COMPLIANCE MEASUREMENTS

Measurements of endothelium-dependent vasoreactivity and arterial comp liance are important metrics of vascular pathophysiology which may be used for the development and evaluation of therapeutic methods, The te chnique of ultrasonic echo tracking is applicable to measurements of e ndothelium-dependent vasoreactivity and arterial compliance, To evalua te the application of echo tracking to these measurements, we construc ted a system based upon analog-to-digital conversion and storage of th e radio frequency (RF) ultrasound signals, Off-line analysis of the RF data with various echo-tracking algorithms demonstrated two potential sources of error: tracking drift and RF transition regions, The track ing drift resulted from the slow accumulation of tracking error, The R F transition regions were associated with disparate motions of neighbo ring reflectors or the insonation of a new series of tissue layers, As a result of these sources of error, the application of echo tracking to endothelium-dependent vasoreactivity measurements is unlikely to ou tperform duplex ultrasound methods, The application of echo tracking t o arterial compliance measurements via the arterial pressure/diameter relationship may produce variable results due to RF transition regions . Finally, the application of echo tracking to arterial compliance mea surements via the pulse wave velocity is relatively insensitive to the se sources of error because the pulse-wave velocity measurement depend s upon the timing of the peak arterial distension, not on the absolute value of the distension.