Acoustic Radiation Force Impulse Imaging on an IVUS Circular Array

Our long-term goal is the detection and characterization of vulnerable plaque in the coronary arteries of the heart using IVUS catheters. Vulnerable plaque, characterized by a thin fibrous cap and a soft, lipid-rich, necrotic core is a pre-cursor to heart attack and stroke. Early detection of such plaques may potentially alter the course of treatment of the patient in order to prevent ischemic events. In this paper, we modified Volcano Visions 8.2 French, 9MHz catheters and Volcano Platinum 3.5 French, 20MHz catheters by short circuiting portions of the array for ARFI applications. The catheters had an effective transmit aperture size of 2mm and 1.5mm respectively. The catheters were connected to a Verasonics scanner and driven with pushing pulses of 180V(p-p) to acquire ARFI data from a soft gel phantom with a Young's modulus of 2.9 kPa. The dynamic response of the tissue-mimicking material demonstrates a typical ARFI motion of 1-2 microns as the gel phantom displaces away and recovers back to its normal position. Our results demonstrate that the generation of radiation force from IVUS catheters and the development of intravascular ARFI may be feasible.