US backscatter and attenuation 30 to 50 MHz and MR T2 at 3 Tesla for differentiation of atherosclerotic artery constituents in vitro.

This study compares quantitative characterization of atherosclerotic artery constituents by high resolution estimates of ultrasonic attenuation, ultrasonic attenuation-compensated backscatter, and magnetic resonance transverse relaxation time. Atherosclerotic human arteries were studied in vitro at 37°C. Backscattered radio frequency signals were acquired with a 50 MHz backscatter acoustic microscope. Ultrasonic parametric images were constructed from the integrated (30 to 50 MHz) backscatter and attenuation obtained using FFT methods with diffraction correction and a multinarrow-band attenuation algorithm. Parametric magnetic resonance images were constructed from calculated values of the transverse relaxation time T2 determined from an 8 echo-single-slice sequence at 3 Tesla. In a total of 54 regions of interest, average values of integrated attenuation, integrated backscatter compensated for the attenuation between the artery surface and the scattering volume, and the transverse relaxation time were correlated with local tissue composition as assessed by histology. Results show that ultrasound and magnetic resonance techniques offer complementary approaches for characterization of plaque composition.