Development of noninvasive parametric imaging of atherosclerotic plaque

The goal of this work is to adapt existing algorithms for the calculation of integrated backscatter (IB) and attenuation (IA) images toward lower frequencies and to test the usefulness of these images for atherosclerotic plaque characterization. Using two different broadband transducers, RF signals from 9 to 50 MHz were collected from a scattering phantom and segments of excised human aorta at 37 degrees C. Local IA and IB estimated from backscattered signals were used to construct parametric images. Local IA in the phantom and aortas was compared to global attenuation measured by double transmission. The ability of parametric images to discriminate variation of plaque composition was assessed by comparing parametric images and artery histologic segments. Good agreement was found between local IA and global attenuation. Work continues toward the development of even lower frequency quantitative images (5 to 28 MHz) for the characterization of carotid plaque. Such a noninvasive technique could improve assessment of plaque risk and guide interventional choices.