Nonlinearly Generated Second Harmonic Ultrasonic Backscatter for Determining Composition of Human Carotid Plaque

Carotid atherosclerotic plaque is a leading cause of stroke. Current imaging approaches measure the extent of stenosis, while plaque composition is unavailable at the point of care outside of calcium burden provided by CT. The goal of this effort is to provide a robust non-invasive measure of plaque composition. The specific focus of this abstract is to determine if the nonlinearly generated second harmonic portion of the signal can aid data obtained from the fundamental portion of the backscatter to determine plaque composition. A pilot clinical study, obtained pulse inversion backscatter from 14 subjects prior to carotid endarterectomy. The corresponding plaque was obtained following surgery and histologically processed. The pulse inversion pairs were processed to obtain the harmonic and fundamental traces with 20dB bandwidths. Power spectrum for each ROI was obtained and normalized by data obtained from a uniform 0.5 dB/cm-MHz phantom and additional attenuation compensation. The results indicate that the harmonic parameters provide additional discriminatory information for plaque composition that is not contained within the fundamental data.