Characterization of Atherosclerotic Plaques and Mural Thrombi With Intravascular Ultrasound Elastography: A Potential Method Evaluated in an Aortic Rabbit Model and a Human Coronary Artery

Abstract

Plaque rupture is correlated with the plaque morphology, composition, mechanical properties, and with the blood pressure. Whereas the geometry can accurately be assessed with intravascular ultrasound (IVUS) imaging, intravascular elastography (IVE) is capable of extracting information on the plaque local mechanical properties and composition. This paper reports additional IVE validation data regarding reproducibility and potential to characterize atherosclerotic plaques and mural thrombi. In a first investigation, radio frequency (RF) data were acquired from the abdominal aorta of an atherosclerotic rabbit model. In a second investigation, IVUS RF data were recorded from the left coronary artery of a patient referred for angioplasty. In both cases, Galaxy IVUS scanners (Boston Scientific, Freemont, CA), equipped with 40 MHz Atlantis catheters, were used. Elastograms were computed using two methods, the Lagrangian speckle model estimator (LSME) and the scaling factor estimator (SFE). Corroborated with histology, the LSME and the SFE both clearly detected a soft thrombus attached to the vascular wall. Moreover, shear elastograms, only available with the LSME, confirmed the presence of the thrombus. Additionally, IVE was found reproducible with consistent elastograms between cardiac cycles (CCs). Regarding the human dataset, only the LSME was capable of identifying a plaque that presumably sheltered a lipid core. Whereas such an assumption could not be certified with histology, radial shear and tangential strain LSME elastograms enabled the same conclusion. It is worth emphasizing that this paper reports the first ever in vivo tangential strain elastogram with regards to vascular imaging, due to the LSME. It is concluded that the IVE was reproducible exhibiting consistent strain patterns between CCs. The IVE might provide a unique tool to assess coronary wall lesions.

Experimental determination of circumferential properties of fresh carotid artery plaques

“…Holzapfel et al (2004 characterised atherosclerotic plaque components from the human carotid artery in both directions, measuring the degree of anisotropic behaviour of atherosclerotic plaques. Other characterisation tests include minimally invasive assessment of atherosclerotic plaques using intravascular ultrasound methods Hiro et al, 1997;Maurice et al, 2008;Richards et al, 2010). In this study, a portable uniaxial tensile tester is used to assess plaque behaviour immediately after being excised through endarterectomy at the Mid-Western Regional Hospital, Limerick, Ireland.…”

Endovascular Repair of Abdominal Aortic Aneurysm: Follow-up with Noninvasive Vascular Elastography in a Canine Model

“…With this preclinical model, we could confirm the feasibility of NIVE for the characterization of endoleaks and thrombus organization after EVAR. The LSME algorithm estimated the strain transmitted by cardiac pulsation inside the aneurysm sac by computing axial and lateral strain and shear maps from RF US images (16)(17)(18)(19). No external compression or radiation force was needed.…”

“…Noninvasive vascular elastography (NIVE) with the Lagrangian speckle model estimator (LSME) measures the deformation induced by natural cardiac pulsation (16)(17)(18). Thus, to generate the elastogram, there is no need to use a low-frequency radiation force, as with the acoustic radiation force impulse imaging technique, or a supersonic shear wave, as with supersonic imaging techniques.…”

Guest Editorial Introduction to the Special Section on Computer Vision for Intravascular and Intracardiac Imaging

“…The method relies on the Lagrangian speckle model estimator to estimate radial/axial as well as circumferential/lateral displacement fields, and shows much promise in characterizing atherosclerotic plaques and mural thrombi [9].…”