IV-ARFI Imaging: Devices and Methods
Coronary heart disease (CHD) affects 15.4 million people and is the leading cause of death in the U.S. CHD involves a buildup of plaque along the vessel wall, which results in a narrowing and hardening of the arteries (atherosclerosis), restricting the supply of blood and oxygen to the heart muscle. Vulnerable plaques, characterized by a thin fibrous cap and a soft, lipid-rich necrotic core, are prone to rupture and can eventuate in a heart attack or stroke.
Our long-term goal is the development of an intravascular ultrasound (IVUS) catheter probe capable of high-resolution acoustic radiation force imaging in the coronary arteries to identify and characterize vulnerable plaque. We are investigating the possibilities of this approach by constructing prototype transducers and performing finite-element simulations of vessel plaque response to an acoustic radiation force impulse (ARFI) excitation.
IV-ARFI simulation: initial results. Top Left: 2.2mm-long cylindrical single-element 'push' transducer. Top Right: 0.7mm-long cylindrical 'tracking' array transducer. Bottom Left: -3dB and -6dB contours of 'push' beam and 'track' beam (focused). Bottom Right: Simulated peak scatterer displacement profile and tracked-displacement (by normalized cross-correlation) image; brightness scale in microns.
IV-ARFI experiment. Left: 2.2mm-long cylindrical single-element transducer. Center: transducer placed in gel phantom. Right: tracked displacement vs. time profiles (5 trials, 19.6 +/- 6.0 micron peak displacement).