ULTRASONIC MEASUREMENT OF DIFFERENTIAL DISPLACEMENT STRAIN IN A VASCULAR MODEL

The potential of intravascular ultrasound imaging for characterizing r egional arterial elasticity was examined in an experimental tissue-equ ivalent vessel model. Differential intrawall displacement measurement, the first step in regional elasticity determination, was investigated using a crosscorrelation tracking algorithm. Calibration studies show ed that tracking accuracy varied significantly with tracking direction (axial versus lateral) and position in the field of the transducer. M idfield geometric error in the axial direction for a nominal displacem ent of 100 mu m was 5.5 mu m whereas the corresponding error in the la teral direction was 31.7 mu m. Displacement was tracked in serial intr avascular images of vessel phantoms acquired during stepwise pressuriz ation experiments from 0-250 mmHg. Two-dimensional grey scale maps of axial, lateral and net intrawall displacement components over the full pressurization range were generated. Displacement profiles demonstrat ed successful detection of differential radial displacement and good c orrelation with theoretical profiles (root mean square difference 3%). The corresponding experimental strain profiles were significantly noi sier (root mean square difference 76%) due to small fluctuations in th e displacement data. This work demonstrates that, with further refinem ent, regional strain mapping in vessel walls with intravascular ultras ound imaging is feasible. Mechanical characterization of arteries may provide a new tool to aid in assessing and treating atherosclerotic le sions. (C) 1997 Dynamedia, Inc.