Strain Imaging of Coronary Arteries with Intraluminal Ultrasound: Experiments on an Inhomogeneous Phantom

doi:10.1006/uimg.1996.0010

Ultrasonic Imaging

Volume 18, Issue 3, July 1996, Pages 173-191

Ultrasonic Imaging

https://doi.org/10.1006/uimg.1996.0010 Get rights and content

Abstract

In coronary arteries, knowing the relative stiffness of atherosclerotic lesions can help physicians select the most appropriate therapeutic modality. Because soft material supports larger strains than hard, measurements of this quantity can distinguish tissue of differing stiffness. In a previous paper, we described techniques for computing displacements and strains in coronary arteries using an integrated angioplasty and imaging catheter. Here, we demonstrate that hard and soft materials in a tissue-mimicking phantom can be differentiated with this device. Because tissue motion cannot be distinguished from catheter motiona priori, we perform all computations in the coordinate system centered at the balloon's geometric center. This reference frame depends only on balloon shape and is independent of catheter motion. A specialized correlation-based, phase-sensitive speckle tracking algorithm has been developed to compute strain. Maximum phantom displacement was about 25 μm, and the maximum radial, normal strain was about 1.5 percent.

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Cited by (53)

Non-Invasive Identification of Vulnerable Atherosclerotic Plaques Using Texture Analysis in Ultrasound Carotid Elastography: An In Vivo Feasibility Study Validated by Magnetic Resonance Imaging
2017, Ultrasound in Medicine and Biology
Citation Excerpt :
The basic principle underlying carotid elastography is that plaque motion and deformation are induced by the physiologic variation in blood pressure, and motion estimation algorithms, such as cross-correlation and optical flow methods, can be used to detect such motion (i.e., displacement and velocity) and deformation (i.e., strain and strain rate) based on the acquired ultrasound images. Various studies have been performed on the elastography of plaques indicating the feasibility of the technique in plaque characterization and risk stratification (de Korte et al. 2000; Hansen et al. 2009; Huang et al. 2016; Kanai et al. 2003; Korukonda and Doyley 2012; Maurice et al. 2004; Ribbers et al. 2007; Shapo et al. 1996; Shi et al. 2008; Wan et al. 2014; Wang et al. 2014; Widman et al. 2015a; Zhang et al. 2015a). The strain distribution of plaque tissues is associated with the stiffness distribution of plaque composition, and higher local strain values are found in softer regions of the plaque (Bonnefous et al. 1996; de Korte et al. 2000; Kanai et al. 2003).
The aims of this study were to quantify the textural information of strain rate images in ultrasound carotid elastography and evaluate the feasibility of using the textural features in discriminating stable and vulnerable plaques with magnetic resonance imaging as an in vivo reference. Ultrasound radiofrequency data were acquired in 80 carotid plaques from 52 patients, mainly in the longitudinal imaging view, and axial strain rate images were estimated with an ultrasound carotid elastography technique based on an optical flow algorithm. Four textural features of strain rate images—contrast, homogeneity, correlation and angular second moment—were derived based on the gray-level co-occurrence matrix in plaque regions to quantify the deformation distribution pattern. Conventional elastographic indices based on the magnitude of the absolute strain rate, such as the maximum, mean, median, standard deviation and 99th percentile of the axial strain rate, were also obtained for comparison. Composition measurement with magnetic resonance imaging identified 30 plaques as vulnerable and the other 50 as stable. The four textural features, as well as the magnitude of strain rate images, significantly differed between the two groups of plaques. The best performing features for plaque classification were found to be the contrast and 99th percentile of the absolute strain rate, with a comparative area under the receiver operating characteristic curve of 0.81; a slightly higher maximum accuracy of plaque classification can be achieved by the textural feature of contrast (83.8% vs. 81.3%). The results indicate that the use of texture analysis in plaque classification is feasible and that larger local deformations and higher level of complexity in deformation patterns (associated with the elastic or stiffness heterogeneity of plaque tissues) are more likely to occur in vulnerable plaques.
Ultrasound-Based Carotid Elastography for Detection of Vulnerable Atherosclerotic Plaques Validated by Magnetic Resonance Imaging
2016, Ultrasound in Medicine and Biology
Citation Excerpt :
Because softer tissues are associated with larger deformation under the same force, elastography was first introduced to detect the pathologic variations in tissue elasticity caused by some diseases such as cancers (Ophir et al. 2000). Later, elastography was adapted for intravascular ultrasound (IVUS) to differentiate between stable and vulnerable atherosclerotic plaques in coronary arteries (de Korte et al. 1997, 2011; Shapo et al. 1996). Different strain values were found for fibrous, fatty and fibrofatty plaques, and IVUS elastography was reported to detect vulnerable plaques with high sensitivity and specificity (de Korte et al. 2000; Schaar et al. 2001).
Ultrasound-based carotid elastography has been developed to estimate the mechanical properties of atherosclerotic plaques. The objective of this study was to evaluate the in vivo capability of carotid elastography in vulnerable plaque detection using high-resolution magnetic resonance imaging as reference. Ultrasound radiofrequency data of 46 carotid plaques from 29 patients (74 ± 5 y old) were acquired and inter-frame axial strain was estimated with an optical flow method. The maximum value of absolute strain rate for each plaque was derived as an indicator for plaque classification. Magnetic resonance imaging of carotid arteries was performed on the same patients to classify the plaques into stable and vulnerable groups for carotid elastography validation. The maximum value of absolute strain rate was found to be significantly higher in vulnerable plaques (2.15 ± 0.79 s⁻¹, n = 27) than in stable plaques (1.21 ± 0.37 s⁻¹, n = 19) (p < 0.0001). Receiver operating characteristic curve analysis was performed, and the area under the curve was 0.848. Therefore, the in vivo capability of carotid elastography to detect vulnerable plaques, validated by magnetic resonance imaging, was proven, revealing the potential of carotid elastography as an important tool in atherosclerosis assessment and stroke prevention.
Echo-computed tomography strain imaging of healthy and diseased carotid specimens
2014, Ultrasound in Medicine and Biology
Citation Excerpt :
The aforementioned IVUS techniques are invasive, use 1-D signal processing and suffer from motion perpendicular to the ultrasound beam. Two-dimensional methods, like speckle tracking (McCormick et al. 2012; Ryan and Foster 1997; Shapo et al. 1996), optical flow methods (Maurice et al. 2008; Wan et al. 2001) and non-rigid image registration (Liang et al. 2008), have been proposed to improve the 1-D methods mentioned above using the B-mode data as input. However, to improve the accuracy and resolution of displacement and strain estimates, RF-based algorithms are more favorable.
To improve our understanding of the mechanical behavior of human atherosclerotic plaque tissue, fully 3-D geometrical, morphological and dynamical information is essential. For this purpose, four-dimensional (3-D+t) strain imaging using an ultrasound tomography approach (echo-computed tomography) was performed in carotid arteries in vitro. The method was applied to a carotid phantom (CPh), a porcine carotid artery (PC) and human carotid atherosclerotic plaque samples (HC, n = 5). Each sample was subjected to an intraluminal pressure, after which 2-D longitudinal ultrasound images were obtained for 36 angles along the circumferential direction. Local deformations were estimated using a 2-D strain algorithm, and 3-D radial strain data were reconstructed. At systole, median luminal strains of 15% (CPh) and 18% (PC) were found, which is in agreement with the stiffness of the material and applied pressure pulse. The elastographic signal-to-noise ratio was consistent in all directions and ranged from 16 to 36 dB. Furthermore, realistic but more complex strain patterns were found for the HC, with 99th percentile systolic strain values ranging from 0.1% to 18%.
Endovascular shear strain elastography for the detection and characterization of the severity of atherosclerotic plaques: In vitro validation and in vivo evaluation
2014, Ultrasound in Medicine and Biology
This work explores the potential of shear strain elastograms to identify vulnerable atherosclerotic plaques. The Lagrangian speckle model estimator (LSME) elasticity imaging method was further developed to estimate shear strain elasticity (SSE). Three polyvinyl alcohol cryogel vessel phantoms were imaged with an intravascular ultrasound (IVUS) scanner. The estimated SSE maps were validated against finite-element results. Atherosclerosis was induced in carotid arteries of eight Sinclair mini-pigs using a combination of surgical techniques, diabetes and a high-fat diet. IVUS images were acquired in vivo in 14 plaques before euthanasia and histology. All plaques were characterized by high magnitudes in SSE maps that correlated with American Heart Association atherosclerosis stage classifications (r = 0.97, p < 0.001): the worse the plaque condition the higher was the absolute value of SSE, i.e. |SSE| (e.g., mean |SSE| was 3.70 ± 0.40% in Type V plaques, whereas it was reduced to 0.11 ± 0.01% in normal walls). This study indicates the feasibility of using SSE to highlight atherosclerotic plaque vulnerability characteristics.
Estimation of the Transverse Strain Tensor in the Arterial Wall Using IVUS Image Registration
2008, Ultrasound in Medicine and Biology
Citation Excerpt :
Another limitation of 1-D elastography is that only strain information in the radial direction is obtained. A natural way to address the aforementioned limitations is to extend the 1-D cross-correlation technique to 2-D. Two-dimensional block-matching techniques have been applied to IVUS elastography (Leung et al. 2006; Mita et al. 2001; Ryan et al. 1997; Shapo et al. 1996a, 1996b). These methods can track 2-D local displacements of the tissue, but assume the motion within each local block is rigid.
Intravascular ultrasound (IVUS) elastography is an imaging technique that obtains the local mechanical properties of the artery wall and atherosclerotic plaques through strain measurements using IVUS. Knowledge of these mechanical properties may provide crucial information that can help in estimating plaque composition and its vulnerability. Here, we present a new method to estimate the transverse strain tensor of the arterial wall based on nonrigid image registration using IVUS images. This method registers a pair of images acquired at a vessel site under different levels of luminal pressure. The 2-D displacement field in the vessel cross-section is estimated from image registration; then the displacement field is used to calculate the 2-D local strain tensor. From the strain tensor, the strain in any direction in the cross-section can be obtained; here, the radial and circumferential strain distributions are presented. This strain estimation method has been validated with synthetic motion IVUS images and evaluated using the IVUS images of a polyvinyl alcohol cryogel phantom. The accuracy of the estimated strain and the ability of the method to overcome IVUS system noise are demonstrated. (E-mail: [email protected])
Measurement of the transverse strain tensor in the coronary arterial wall from clinical intravascular ultrasound images
2008, Journal of Biomechanics
Citation Excerpt :
Introduced by Ophir and colleagues (Cespedes et al., 1993; Ophir et al., 1991), elastography is an imaging technique that uses ultrasound to relate the deformation (strain) of a tissue to its mechanical properties. Since then, intravascular applications have been developed (Brusseau et al., 2001; de Korte et al., 1997; Ryan and Foster, 1997; Shapo et al., 1996; Talhami et al., 1994; Wan et al., 2001). de Korte et al. (Cespedes et al., 1997; de Korte et al., 1997) have used IVUS elastography to obtain vascular elastic properties; they measure radial strain by correlation analysis of RF signals recorded under different luminal pressures.
Atherosclerotic plaque rupture is the major cause of acute coronary syndromes. Currently, there is no reliable diagnostic tool to predict plaque rupture. Knowledge of plaque mechanical properties based on local artery wall strain measurements would be useful for characterizing its composition and predicting its vulnerability. Due to cardiac motion, strain estimation in clinical intravascular ultrasound (IVUS) images is extremely challenging. A method is presented to estimate cross-sectional coronary artery wall strain in response to cardiac pulsatile pressure using clinically acquired IVUS images, which are acquired in continuous pullback mode. First, cardiac phase information is retrieved retrospectively from an IVUS image sequence using an image-based gating method, and image sub-sequences at systole and diastole are extracted. Then, images at branch sites are used as landmarks to align the two image sub-sequences. Finally, the paired images at each site are registered to measure the 2D strain tensor of the coronary artery cross-section. This method has been successfully applied to IVUS images of a left anterior descending (LAD) coronary artery acquired clinically during a standard procedure. Such complete strain information should be useful for identifying vulnerable plaque.

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Regular ArticleStrain Imaging of Coronary Arteries with Intraluminal Ultrasound: Experiments on an Inhomogeneous Phantom

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Regular Article
Strain Imaging of Coronary Arteries with Intraluminal Ultrasound: Experiments on an Inhomogeneous Phantom