The Experts below are selected from a list of 18456 Experts worldwide ranked by ideXlab platform
Morton H. Friedman - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the 3D arterial wall Strain Tensor using intravascular B-mode ultrasound images: a feasibility study.
Physics in Medicine and Biology, 2010Co-Authors: Yun Liang, Morton H. FriedmanAbstract:Intravascular ultrasound (IVUS) elastography is a promising tool for studying atherosclerotic plaque composition and assessing plaque vulnerability. Current IVUS elastography techniques can measure the 1D or 2D Strain of the vessel wall using various motion tracking algorithms. Since biological soft tissue tends to deform non-uniformly in 3D, measurement of the complete 3D Strain Tensor is desirable for more rigorous analysis of arterial wall mechanics. In this paper, we extend our previously developed method of 2D arterial wall Strain measurement based on non-rigid image registration into 3D Strain measurement. The new technique registers two image volumes acquired from the same vessel segment under different levels of luminal pressure and longitudinal stress. The 3D displacement field obtained from the image registration is used to calculate the local 3D Strain Tensor. From the 3D Strain Tensor, radial, circumferential and longitudinal Strain distributions can be obtained and displayed. This Strain Tensor measurement method is validated and evaluated using IVUS images of healthy porcine carotid arteries subjected to a luminal pressure increase and longitudinal stretch. The ability of the algorithm to overcome systematic noise was tested, as well as the consistency of the results under different longitudinal frame resolutions.
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estimation of the transverse Strain Tensor in the arterial wall using ivus image registration
Ultrasound in Medicine and Biology, 2008Co-Authors: Yun Liang, Hui Zhu, Morton H. FriedmanAbstract: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.
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measurement of the transverse Strain Tensor in the coronary arterial wall from clinical intravascular ultrasound images
Journal of Biomechanics, 2008Co-Authors: Yun Liang, Hui Zhu, Thomas R Gehrig, Morton H. FriedmanAbstract: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.
Jerry L Prince - One of the best experts on this subject based on the ideXlab platform.
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identification of myocardial infarction using three dimensional Strain Tensor fractional anisotropy
International Symposium on Biomedical Imaging, 2010Co-Authors: Sahar Soleimanifard, Khaled Z Abdelmoniem, Harsh K Agarwal, Miguel Santaularia Tomas, Tetsuo Sasano, Evertjan Vonken, Amr Youssef, Roselle M Abraham, Theodore P Abraham, Jerry L PrinceAbstract:Accurate localization of myocardial viability is important in diagnosis of infarction. Regional Strain function provides excessive information for clinical decision making but comparison of Strain Tensor profiles across differing tissue types is usually difficult due to multi-variate nature of Tensors. It is desirable to describe Tensors with simplified scalar indices which are more mathematically and statistically intuitive. In this work, anisotropy of Tensors in healthy and experimental infarct regions in a large animal model is assessed and compared to directional components of Strain Tensors which are currently the most popular indices in active use. Myocardial Strain Tensors are computed using zHARP, a magnetic resonance (MR) tagging technique that provides quantification of cardiac function with direct computation of three-dimensional Tensors from two-dimensional short axis MR images. Fractional anisotropy of Strain Tensors shows high correlation with late gadolinium enhanced images and is capable of discrimination between healthy and infarcted regions.
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direct three dimensional myocardial Strain Tensor quantification and tracking using zharp
Medical Image Analysis, 2008Co-Authors: Khaled Z Abdelmoniem, Matthias Stuber, Jerry L PrinceAbstract:Images of myocardial Strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3D) Strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3D Strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3D Strain Tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D Strain Tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in vitro on a phantom and in vivo in four healthy adult human subjects.
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multi slice three dimensional myocardial Strain Tensor quantification using zharp
Information Processing in Medical Imaging, 2007Co-Authors: Khaled Z Abdelmoniem, Matthias Stuber, Jerry L PrinceAbstract:In this article we propose a novel method for calculating cardiac 3-D Strain. The method requires the acquisition of myocardial short-axis (SA) slices only and produces the 3-D Strain Tensor at every point within every pair of slices. Three-dimensional displacement is calculated from SA slices using zHARP which is then used for calculating the local displacement gradient and thus the local Strain Tensor. There are three main advantages of this method. First, the 3-D Strain Tensor is calculated for every pixel without interpolation; this is unprecedented in cardiac MR imaging. Second, this method is fast, in part because there is no need to acquire long-axis (LA) slices. Third, the method is accurate because the 3-D displacement components are acquired simultaneously and therefore reduces motion artifacts without the need for registration. This article presents the theory of computing 3-D Strain from two slices using zHARP, the imaging protocol, and both phantom and in-vivo validation.
Frederic Masson - One of the best experts on this subject based on the ideXlab platform.
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large scale velocity field and Strain Tensor in iran inferred from gps measurements new insight for the present day deformation pattern within ne iran
Geophysical Journal International, 2007Co-Authors: Frederic Masson, Mohammad Anvari, Y Djamour, Andrea Walpersdorf, F Tavakoli, Marc Daignieres, Hamid Reza Nankali, Sebastien Van GorpAbstract:SUMMARY A network of 26 GPS sites was implemented in Iran and Northern Oman to measure displacements in this part of the Arabia‐Eurasia collision zone. We present the GPS velocity field obtained from three surveys performed in 1999 September, 2001 October and 2005 September and the deduced Strain Tensor. This study refines previous studies inferred from only the two first surveys. Improvements are significant in NE Iran. The present-day shortening rate across the mountain belts of NE Iran is estimated to 5 ± 1m m yr −1 at about N11 ◦ ,2 ± 1m m yr −1 of NS shortening across the eastern Kopet Dag and 3 ± 1m m yr −1 of NS shortening across Binalud and Kuh-e-Sorkh. Our GPS measurements emphasize the varying character of the Kopet Dag deformation between its southeastern part with prevailing thrusting at low rates and its northwestern part with dominant strike-slip activity at increasing rates. The principal axes of the horizontal Strain Tensor appears very homogeneous from the Zagros to the Alborz and the Kopet-Dag (N20 ◦ ) and in eastern Iran (Makran and Lut block: N30 ◦ ). Only NW Iran suffers a variable Strain pattern which seems to wrap the Caspian basin. The Strain Tensor map underlines the existence of large homogeneous tectonic provinces in terms of style and amplitude of the deformation.
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large scale velocity field and Strain Tensor in iran inferred from gps measurements new insight for the present day deformation pattern within ne iran
Geophysical Journal International, 2007Co-Authors: Frederic Masson, Mohammad Anvari, Y Djamour, Andrea Walpersdorf, F Tavakoli, Marc Daignieres, Hamid Reza Nankali, Sebastien Van GorpAbstract:A network of 26 GPS sites was implemented in Iran and Northern Oman to measure displacements in this part of the Arabia–Eurasia collision zone. We present the GPS velocity field obtained from three surveys performed in 1999 September, 2001 October and 2005 September and the deduced Strain Tensor. This study refines previous studies inferred from only the two first surveys. Improvements are significant in NE Iran. The present-day shortening rate across the mountain belts of NE Iran is estimated to 5 ± 1 mm yr−1 at about N11°, 2 ± 1 mm yr−1 of NS shortening across the eastern Kopet Dag and 3 ± 1 mm yr−1 of NS shortening across Binalud and Kuh-e-Sorkh. Our GPS measurements emphasize the varying character of the Kopet Dag deformation between its southeastern part with prevailing thrusting at low rates and its northwestern part with dominant strike-slip activity at increasing rates. The principal axes of the horizontal Strain Tensor appears very homogeneous from the Zagros to the Alborz and the Kopet-Dag (N20°) and in eastern Iran (Makran and Lut block: N30°). Only NW Iran suffers a variable Strain pattern which seems to wrap the Caspian basin. The Strain Tensor map underlines the existence of large homogeneous tectonic provinces in terms of style and amplitude of the deformation.
Yun Liang - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the 3D arterial wall Strain Tensor using intravascular B-mode ultrasound images: a feasibility study.
Physics in Medicine and Biology, 2010Co-Authors: Yun Liang, Morton H. FriedmanAbstract:Intravascular ultrasound (IVUS) elastography is a promising tool for studying atherosclerotic plaque composition and assessing plaque vulnerability. Current IVUS elastography techniques can measure the 1D or 2D Strain of the vessel wall using various motion tracking algorithms. Since biological soft tissue tends to deform non-uniformly in 3D, measurement of the complete 3D Strain Tensor is desirable for more rigorous analysis of arterial wall mechanics. In this paper, we extend our previously developed method of 2D arterial wall Strain measurement based on non-rigid image registration into 3D Strain measurement. The new technique registers two image volumes acquired from the same vessel segment under different levels of luminal pressure and longitudinal stress. The 3D displacement field obtained from the image registration is used to calculate the local 3D Strain Tensor. From the 3D Strain Tensor, radial, circumferential and longitudinal Strain distributions can be obtained and displayed. This Strain Tensor measurement method is validated and evaluated using IVUS images of healthy porcine carotid arteries subjected to a luminal pressure increase and longitudinal stretch. The ability of the algorithm to overcome systematic noise was tested, as well as the consistency of the results under different longitudinal frame resolutions.
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estimation of the transverse Strain Tensor in the arterial wall using ivus image registration
Ultrasound in Medicine and Biology, 2008Co-Authors: Yun Liang, Hui Zhu, Morton H. FriedmanAbstract: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.
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measurement of the transverse Strain Tensor in the coronary arterial wall from clinical intravascular ultrasound images
Journal of Biomechanics, 2008Co-Authors: Yun Liang, Hui Zhu, Thomas R Gehrig, Morton H. FriedmanAbstract: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.
Khaled Z Abdelmoniem - One of the best experts on this subject based on the ideXlab platform.
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identification of myocardial infarction using three dimensional Strain Tensor fractional anisotropy
International Symposium on Biomedical Imaging, 2010Co-Authors: Sahar Soleimanifard, Khaled Z Abdelmoniem, Harsh K Agarwal, Miguel Santaularia Tomas, Tetsuo Sasano, Evertjan Vonken, Amr Youssef, Roselle M Abraham, Theodore P Abraham, Jerry L PrinceAbstract:Accurate localization of myocardial viability is important in diagnosis of infarction. Regional Strain function provides excessive information for clinical decision making but comparison of Strain Tensor profiles across differing tissue types is usually difficult due to multi-variate nature of Tensors. It is desirable to describe Tensors with simplified scalar indices which are more mathematically and statistically intuitive. In this work, anisotropy of Tensors in healthy and experimental infarct regions in a large animal model is assessed and compared to directional components of Strain Tensors which are currently the most popular indices in active use. Myocardial Strain Tensors are computed using zHARP, a magnetic resonance (MR) tagging technique that provides quantification of cardiac function with direct computation of three-dimensional Tensors from two-dimensional short axis MR images. Fractional anisotropy of Strain Tensors shows high correlation with late gadolinium enhanced images and is capable of discrimination between healthy and infarcted regions.
-
direct three dimensional myocardial Strain Tensor quantification and tracking using zharp
Medical Image Analysis, 2008Co-Authors: Khaled Z Abdelmoniem, Matthias Stuber, Jerry L PrinceAbstract:Images of myocardial Strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3D) Strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3D Strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3D Strain Tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D Strain Tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in vitro on a phantom and in vivo in four healthy adult human subjects.
-
multi slice three dimensional myocardial Strain Tensor quantification using zharp
Information Processing in Medical Imaging, 2007Co-Authors: Khaled Z Abdelmoniem, Matthias Stuber, Jerry L PrinceAbstract:In this article we propose a novel method for calculating cardiac 3-D Strain. The method requires the acquisition of myocardial short-axis (SA) slices only and produces the 3-D Strain Tensor at every point within every pair of slices. Three-dimensional displacement is calculated from SA slices using zHARP which is then used for calculating the local displacement gradient and thus the local Strain Tensor. There are three main advantages of this method. First, the 3-D Strain Tensor is calculated for every pixel without interpolation; this is unprecedented in cardiac MR imaging. Second, this method is fast, in part because there is no need to acquire long-axis (LA) slices. Third, the method is accurate because the 3-D displacement components are acquired simultaneously and therefore reduces motion artifacts without the need for registration. This article presents the theory of computing 3-D Strain from two slices using zHARP, the imaging protocol, and both phantom and in-vivo validation.