The Imaging Modulography Technique Revisited for High-Definition Intravascular Ultrasound: Theoretical Framework

Abstract

Mechanical characterization of atherosclerotic lesions remains an essential step for the detection of vulnerable plaques (VPs). Recently, an intravascular ultrasound (IVUS) elasticity reconstruction method (iMOD) has been tested in vivo by our group. The major limitation of iMOD is the need to estimate the strain field in the entire VP despite attenuated depth penetration signals when using high-definition (HD) IVUS systems. Therefore, an extended iMOD approach (E-iMOD) was designed and applied to coronary lesions of patients imaged in vivo with IVUS. The E-iMOD method (i) quantified necrotic core areas with a mean absolute relative error of 3.5 ± 3.5% and (ii) identified Young's moduli of the necrotic cores and fibrous regions with mean values of 5.7 ± 0.8 kPa and 794.5 ± 22.0 kPa instead of 5 kPa and 800 kPa, respectively. This study demonstrates the potential of the improved HD-IVUS modulography technique E-iMOD to characterize coronary VPs.

Characterizing atherosclerotic tissues: in silico analysis of mechanical properties using intravascular ultrasound and inverse finite element methods

“…However, the estimated values were far from the actual ones. Similar outcomes were reported by Le Floc'h et al ( 2009) and Tacheau et al (2016) who successfully identified calcium inclusions but failed to accurately estimate their Young's modulus due to the small strains amplitudes. Nevertheless, the differences between considering the actual or the estimated Young's modulus did not affect the radial strains map.…”

“…We computed the strains in both Cartesian and cylindrical coordinates, as well as the principal and equivalent strains. However, to be consistent with prior studies (Le Floc'h et al, 2009;Le Floc'h et al, 2012;Tacheau et al, 2016), we mainly utilized radial strains for the segmentation and optimization process due to their lower estimation error from IVUS images compared to other deformation variables.…”

“…Frontiers in Bioengineering and Biotechnology frontiersin.org Frontiers in Bioengineering and Biotechnology frontiersin.org pressurized state at 110 mmHg, assuming a linear elastic behavior of the tissues. Thus, this pressurized reference could lead to Young's modulus acquisition (Le Floc'h et al, 2009;Bouvier et al, 2013;Tacheau et al, 2016) or orthotropic linear properties (Gómez et al, 2019). However, this assumption was not valid for estimating non-linear materials, such as soft tissues.…”

Coronary artery properties in atherosclerosis: A deep learning predictive model

“…One promising approach is the iMOD elastography ( Le Floc’h et al., 2010 ), which developed several computational algorithms to rebuild elasticity strain maps inside the wall based on the prediction of the stress maps using IVUS-derived techniques. Since 2009, some remarkable improvements have been developed, such as two powerful stability plaque bio-markers of the coronary artery based on radial strains and its gradient, which allow Young’s modulus to be obtained under linear isotropic elasticity, plane strain, and incompressibility hypothesis ( Le Floc’h et al., 2009 ; Tacheau et al., 2016 ; Gómez et al., 2019 ). However, all these methods share a common issue: the waiting time between acquiring the image and obtaining the results from the computational model is prolonged due to the need to optimize the problem specific to the patient.…”

Intraluminal Ultrasonic Palpation Imaging Technique Revisited for Anisotropic Characterization of Healthy and Atherosclerotic Coronary Arteries: A Feasibility Study

“…Nevertheless, complex non-linear geometric effects do not allow a direct correlation between the measured spatial strain field and the mechanical property of the tissue. By using the IVUS strain field inside atherosclerotic plaques (De Korte et al 2002;Doyley 2012;Maurice et al 2004aMaurice et al , 2007, several elasticity reconstruction approaches have been developed to characterize the entire lesion (Baldewsing et al 2007;Del eaval et al 2013;Doyley 2012;Le Floc'h et al 2009, 2012Nayak et al 2017;Poree et al 2017;Richards and Doyley 2011;Richards et al 2015;Tacheau et al 2016) and to delineate a subendoluminal layer of the arterial wall called the palpography domain (C espedes et al 2000;Del eaval et al 2013;Doyley et al 2001;Schaar et al 2005;Widynski et al 2014). Both techniques aim to characterize the mechanical properties of atherosclerotic lesions and ultimately differentiate vulnerable from stable plaques.…”