Ahmed M. Ehab Mahmoud MSc, PhD, Presenter: Nothing to Disclose

Debaditya Dutta MS, PhD, Abstract Co-Author: Nothing to Disclose

Linda Lavery BS, Abstract Co-Author: Nothing to Disclose

Kang Kim PhD, Abstract Co-Author: Nothing to Disclose

Ultrasound (US) elasticity imaging (UEI) is able to measure the mechanical changes in vessel wall accompanying the development of atherosclerotic plaque (AP), while US thermal strain imaging (TSI) can detect lipid contents in AP. In this study, we demonstrate in vivo feasibility of imaging both the mechanical and compositional changes of AP non-invasively using novel hybrid UEI-TSI technique.

An optimal UEI-TSI heating/imaging pulse sequence was developed on a commercial US scanner. A well-established atherosclerotic rabbit model was followed to induce AP in rabbit femoral arteries (n=6) by introducing a balloon injury while high-fat high-cholesterol diet was administered. During UEI-TSI scanning of AP in rabbit femoral arteries, US radio frequency data were acquired for approximately 8 seconds along with US Doppler images. Mechanical displacements due to inter-cardiac pulsation and temporal displacements due to sound speed changes caused by temperature increase (≤ 2Co) in tissues were estimated using 2D phase-sensitive speckle tracking. Vessels were harvested at time points including 4, 8, 12 weeks for histology using Oil-Red-O lipid staining.

Lipid contents within AP showed distinct positive strains (≈ +0.18%) in TSI images upon slight temperature increase (≤ 2Co), while surrounding water-based tissues showed negative or zero strains. In UEI strain maps, sites undergoing AP showed compressional strain values (≈ -0.44%) higher than those developed in normal vascular walls, which correlate well with the known elastic characteristics of soft lipid-rich lesions. Results of the UEI-TSI hybrid imaging showed good agreement with US Doppler and histology.

The hybrid UEI-TSI imaging technique was able to assess successfully both mechanical and compositional characteristics of AP in the femoral artery of atherosclerotic rabbit model in vivo. The co-registered complete set of morphological, mechanical, and compositional information obtained by the hybrid UEI-TSI imaging highly correlated with histopathological findings, and shall complement other modalities in diagnosing and assessing AP vulnerability.

This study demonstrated the feasibility of the hybrid UEI-TSI technique to assess AP vulnerability, and can eventually form a foundation for translating this imaging technique to clinics.

Mahmoud, A, Dutta, D, Lavery, L, Kim, K, A Novel Ultrasound-based Hybrid Imaging Technique for Non-invasive Assessment of Mechanical and Compositional Characteristics of Atherosclerotic Plaques: In Vivo Animal Study.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12034575.html