1
|
Rakibuzzaman M, Kim HH, Suh SH, Lee BK, Kwon HM, Zhou L. Simulation of stress in a blood vessel due to plaque sediments in coronary artery disease. Biomed Phys Eng Express 2024; 10:045036. [PMID: 38806008 DOI: 10.1088/2057-1976/ad50da] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 05/28/2024] [Indexed: 05/30/2024]
Abstract
Atherosclerosis is a cardiovascular disease mainly caused by plaque deposition in blood vessels. Plaque comprises components such as thrombosis, fibrin, collagen, and lipid core. It plays an essential role in inducing rupture in a blood vessel. Generally, Plaque could be described as three kinds of elastic models: cellular Plaque, hypocellular Plaque, and calcified Plaque. The present study aimed to investigate the behavior of atherosclerotic plaque rupture according to different lipid cores using Fluid-Structure Interaction (FSI). The blood vessel was also varied with different thicknesses (0.05, 0.25, and 0.5 mm). In this study, FSI simulation with a cellular plaque model with various thicknesses was investigated to obtain information on plaque rupture. Results revealed that the blood vessel with Plaque having a lipid core represents higher stresses than those without a lipid core. Blood vessels' thin thickness, like a thin cap, results in more considerable than Von Mises stress. The result also suggests that even at low fracture stress, the risk of rupture due to platelet decomposition at the gap was more significant for cellular plaques.
Collapse
Affiliation(s)
- Md Rakibuzzaman
- Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang, 212013, People's Republic of China
- Department of Mechanical Engineering, International University of Business Agriculture and Technology, Dhaka, 1230, Bangladesh
| | - Hyoung-Ho Kim
- School of Mechanical Material Convergence Engineering, Gyeongsang National University, Jinju, 52725, Republic of Korea
| | - Sang-Ho Suh
- School of Mechanical Engineering, Soongsil University, Seoul, 06978, Republic of Korea
| | - Byoung-Kwon Lee
- Department of Internal Medicine, Gangnam Severance Hospital, 211 Eonju-ro, Gangnam-Gu, Seoul, 06273, Republic of Korea
| | - Hyuck Moon Kwon
- Department of Internal Medicine, Gangnam Severance Hospital, 211 Eonju-ro, Gangnam-Gu, Seoul, 06273, Republic of Korea
| | - Ling Zhou
- Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang, 212013, People's Republic of China
| |
Collapse
|
2
|
Pruijssen JT, Schreuder FHBM, Wilbers J, Kaanders JHAM, de Korte CL, Hansen HHG. Performance evaluation of commercial and non-commercial shear wave elastography implementations for vascular applications. ULTRASONICS 2024; 140:107312. [PMID: 38599075 DOI: 10.1016/j.ultras.2024.107312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 03/25/2024] [Accepted: 04/01/2024] [Indexed: 04/12/2024]
Abstract
BACKGROUND Shear wave elastography (SWE) is mainly used for stiffness estimation of large, homogeneous tissues, such as the liver and breasts. However, little is known about its accuracy and applicability in thin (∼0.5-2 mm) vessel walls. To identify possible performance differences among vendors, we quantified differences in measured wave velocities obtained by commercial SWE implementations of various vendors over different imaging depths in a vessel-mimicking phantom. For reference, we measured SWE values in the cylindrical inclusions and homogeneous background of a commercial SWE phantom. Additionally, we compared the accuracy between a research implementation and the commercially available clinical SWE on an Aixplorer ultrasound system in phantoms and in vivo in patients. METHODS SWE measurements were performed over varying depths (0-35 mm) using three ultrasound machines with four ultrasound probes in the homogeneous 20 kPa background and cylindrical targets of 10, 40, and 60 kPa of a multi-purpose phantom (CIRS-040GSE) and in the anterior and posterior wall of a homogeneous polyvinyl alcohol vessel-mimicking phantom. These phantom data, along with in vivo SWE data of carotid arteries in 23 patients with a (prior) head and neck neoplasm, were also acquired in the research and clinical mode of the Aixplorer ultrasound machine. Machine-specific estimated phantom stiffness values (CIRS phantom) or wave velocities (vessel phantom) over all depths were visualized, and the relative error to the reference values and inter-frame variability (interquartile range/median) were calculated. Correlations between SWE values and target/vessel wall depth were explored in phantoms and in vivo using Spearman's correlations. Differences in wave velocities between the anterior and posterior arterial wall were assessed with Wilcoxon signed-rank tests. Intra-class correlation coefficients were calculated for a sample of ten patients as a measure of intra- and interobserver reproducibility of SWE analyses in research and clinical mode. RESULTS There was a high variability in obtained SWE values among ultrasound machines, probes, and, in some cases, with depth. Compared to the homogeneous CIRS-background, this variation was more pronounced for the inclusions and the vessel-mimicking phantom. Furthermore, higher stiffnesses were generally underestimated. In the vessel-mimicking phantom, anterior wave velocities were (incorrectly) higher than posterior wave velocities (3.4-5.6 m/s versus 2.9-5.9 m/s, p ≤ 0.005 for 3/4 probes) and remarkably correlated with measurement depth for most machines (Spearman's ρ = -0.873-0.969, p < 0.001 for 3/4 probes). In the Aixplorer's research mode, this difference was smaller (3.3-3.9 m/s versus 3.2-3.6 m/s, p = 0.005) and values did not correlate with measurement depth (Spearman's ρ = 0.039-0.659, p ≥ 0.002). In vivo, wave velocities were higher in the posterior than the anterior vessel wall in research (left p = 0.001, right p < 0.001) but not in clinical mode (left: p = 0.114, right: p = 0.483). Yet, wave velocities correlated with vessel wall depth in clinical (Spearman's ρ = 0.574-0.698, p < 0.001) but not in research mode (Spearman's ρ = -0.080-0.466, p ≥ 0.003). CONCLUSIONS We observed more variation in SWE values among ultrasound machines and probes in tissue with high stiffness and thin-walled geometry than in low stiffness, homogeneous tissue. Together with a depth-correlation in some machines, where carotid arteries have a fixed location, this calls for caution in interpreting SWE results in clinical practice for vascular applications.
Collapse
Affiliation(s)
- Judith T Pruijssen
- Medical Ultrasound Imaging Center (MUSIC), Department of Medical Imaging/Radiology, Radboud university medical center, Nijmegen, the Netherlands.
| | - Floris H B M Schreuder
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Joyce Wilbers
- Center of Expertise for Cancer Survivorship, Radboud university medical center, Nijmegen, the Netherlands
| | - Johannes H A M Kaanders
- Department of Radiation Oncology, Radboud university medical center, Nijmegen, the Netherlands
| | - Chris L de Korte
- Medical Ultrasound Imaging Center (MUSIC), Department of Medical Imaging/Radiology, Radboud university medical center, Nijmegen, the Netherlands; Physics of Fluid Group, MESA+ Institute for Nanotechnology, and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Hendrik H G Hansen
- Medical Ultrasound Imaging Center (MUSIC), Department of Medical Imaging/Radiology, Radboud university medical center, Nijmegen, the Netherlands
| |
Collapse
|
3
|
Nordenfur T, Caidahl K, Grishenkov D, Maksuti E, Marlevi D, Urban MW, Larsson M. Safety of arterial shear wave elastography- ex-vivoassessment of induced strain and strain rates. Biomed Phys Eng Express 2022; 8. [PMID: 35797069 DOI: 10.1088/2057-1976/ac7f39] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 07/06/2022] [Indexed: 01/18/2023]
Abstract
Shear wave elastography (SWE) is a promising technique for characterizing carotid plaques and assessing local arterial stiffness. The mechanical stress to which the tissue is subjected during SWE using acoustic radiation force (ARF), leading to strain at a certain strain rate, is still relatively unknown. Because SWE is increasingly used for arterial applications where the mechanical stress could potentially lead to significant consequences, it is important to understand the risks of SWE- induced strain and strain rate. The aim of this study was to investigate the safety of SWE in terms of induced arterial strain and strain rateex-vivoand in a human carotid arteryin-vivo. SWE was performed on six porcine aortae as a model of the human carotid artery using different combinations of ARF push parameters (push voltage: 60/90 V, aperture width: f/1.0/1.5, push length: 100/150/200 μs) and distance to push position. The largest induced strain and strain rate were 1.46 % and 54 s-1(90 V, f/1.0, 200 μs), respectively. Moreover, the SWE-induced strains and strain rates increased with increasing push voltage, aperture, push length, and decreasing distance between the region of interest and the push. In the human carotid artery, the SWE-induced maximum strain was 0.06 % and the maximum strain rate was 1.58 s-1, compared with the maximum absolute strain and strain rate of 12.61 % and 5.12 s-1, respectively, induced by blood pressure variations in the cardiac cycle. Our results indicate thatex-vivoarterial SWE does not expose the artery to higher strain rate than normal blood pressure variations, and to strain one order of magnitude higher than normal blood pressure variations, at the push settings and distances from the region of interest used in this study.
Collapse
Affiliation(s)
- Tim Nordenfur
- Department of Biomedical Engineering and Health Systems, KTH, Kungliga Tekniska högskolan, Stockholm, 100 44, SWEDEN
| | - Kenneth Caidahl
- Department of Clinical Physiology, Karolinska University Hospital, Solnavägen 1, Solna, 171 77, SWEDEN
| | - Dmitry Grishenkov
- Department of Biomedical Engineering and Health Systems, KTH, KTH, Stockholm, 100 44, SWEDEN
| | - Elira Maksuti
- Dept. of Physiology and Pharmacology, Anaesthesiology and Intensive Care, Karolinska Institute, Solnavägen 1, Solna, 171 77, SWEDEN
| | - David Marlevi
- Dept. Molecular Medicine and Surgery, Karolinska Institute, Solnavägen 1, Solna, 171 77, SWEDEN
| | - Matthew W Urban
- Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, Minnesota, 55905, UNITED STATES
| | - Matilda Larsson
- Department of Biomedical Engineering and Health Systems, KTH Royal Institute of Technology, KTH, Stockholm, 100 44, SWEDEN
| |
Collapse
|
4
|
Pruijssen JT, de Korte CL, Voss I, Hansen HHG. Vascular Shear Wave Elastography in Atherosclerotic Arteries: A Systematic Review. ULTRASOUND IN MEDICINE & BIOLOGY 2020; 46:2145-2163. [PMID: 32620385 DOI: 10.1016/j.ultrasmedbio.2020.05.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 05/15/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
Ischemic stroke is a leading cause of death and disability worldwide, so adequate prevention strategies are crucial. However, current stroke risk stratification is based on epidemiologic studies and is still suboptimal for individual patients. The aim of this systematic review was to provide a literature overview on the feasibility and diagnostic value of vascular shear wave elastography (SWE) using ultrasound (US) in (mimicked) human and non-human arteries affected by different stages of atherosclerotic diseases or diseases related to atherosclerosis. An online search was conducted on Pubmed, Embase, Web of Science and IEEE databases to identify studies using US SWE for the assessment of vascular elasticity. A quality assessment was performed using Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) checklist, and relevant data were extracted. A total of 19 studies were included: 10 with human patients and 9 with non-human subjects (i.e., [excised] animal arteries and polyvinyl alcohol phantoms). All studies revealed the feasibility of using US SWE to assess individually stiffness of the arterial wall and plaques. Quantitative elasticity values were highly variable between studies. However, within studies, SWE could detect statistically significant elasticity differences in patient/subject characteristics and could distinguish different plaque types with good reproducibility. US SWE, with its unique ability to assess the elasticity of the vessel wall and plaque throughout the cardiac cycle, might be a good candidate to improve stroke risk stratification. However, more clinical studies have to be performed to assess this technique's exact clinical value.
Collapse
Affiliation(s)
- Judith T Pruijssen
- Medical Ultrasound Imaging Centre (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Chris L de Korte
- Medical Ultrasound Imaging Centre (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands; Physics of Fluid Group, MESA+ Institute for Nanotechnology, and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Iona Voss
- Medical Ultrasound Imaging Centre (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hendrik H G Hansen
- Medical Ultrasound Imaging Centre (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| |
Collapse
|
5
|
Herickhoff CD, Telichko AV, Dahl JJ. Cylindrical Transducer for Intravascular ARFI Imaging: Design and Feasibility. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:760-769. [PMID: 31545716 DOI: 10.1109/tuffc.2019.2942347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Intravascular acoustic radiation force impulse (IV-ARFI) imaging has the potential to identify vulnerable atherosclerotic plaques and improve clinical treatment decisions and outcomes for patients with coronary heart disease. Our long-term goal is to develop a thin, flexible catheter probe that does not require mechanical rotation to achieve high-resolution IV-ARFI imaging. In this work, we propose a novel cylindrical transducer array design for IV-ARFI imaging and investigate the feasibility of this approach. We present the construction of a 2.2-mm-long, 4.6-Fr cylindrical prototype transducer to demonstrate generating large ARFI displacements from a small toroidal beam, and we also present simulations of the proposed IV-ARFI cylindrical array design using Field II and a cylindrical finite-element model of vascular tissues and soft plaques. The prototype transducer was found to generate peak radial displacements of over [Formula: see text] in soft gelatin phantoms, and simulations demonstrate the ability of the array design to obtain ARFI images and distinguish soft plaque targets from surrounding, stiffer vessel wall tissue. These results suggest that high-resolution IV-ARFI imaging is possible using a cylindrical transducer array.
Collapse
|
6
|
Torres G, Czernuszewicz TJ, Homeister JW, Caughey MC, Huang BY, Lee ER, Zamora CA, Farber MA, Marston WA, Huang DY, Nichols TC, Gallippi CM. Delineation of Human Carotid Plaque Features In Vivo by Exploiting Displacement Variance. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2019; 66:481-492. [PMID: 30762544 PMCID: PMC7952026 DOI: 10.1109/tuffc.2019.2898628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
While in vivo acoustic radiation force impulse (ARFI)-induced peak displacement (PD) has been demonstrated to have high sensitivity and specificity for differentiating soft from stiff plaque components in patients with carotid plaque, the parameter exhibits poorer performance for distinguishing between plaque features with similar stiffness. To improve discrimination of carotid plaque features relative to PD, we hypothesize that signal correlation and signal-to-noise ratio (SNR) can be combined, outright or via displacement variance. Plaque feature detection by displacement variance, evaluated as the decadic logarithm of the variance of acceleration and termed "log(VoA)," was compared to that achieved by exploiting SNR, cross correlation coefficient, and ARFI-induced PD outcome metrics. Parametric images were rendered for 25 patients undergoing carotid endarterectomy, with spatially matched histology confirming plaque composition and structure. On average, across all plaques, log(VoA) was the only outcome metric with values that statistically differed between regions of lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), collagen (COL), and calcium (CAL). Further, log(VoA) achieved the highest contrast-to-noise ratio (CNR) for discriminating between LRNC and IPH, COL and CAL, and grouped soft (LRNC and IPH) and stiff (COL and CAL) plaque components. More specifically, relative to the previously demonstrated ARFI PD parameter, log(VoA) achieved 73% higher CNR between LRNC and IPH and 59% higher CNR between COL and CAL. These results suggest that log(VoA) enhances the differentiation of LRNC, IPH, COL, and CAL in human carotid plaques, in vivo, which is clinically relevant to improving stroke risk prediction and medical management.
Collapse
|
7
|
Marlevi D, Maksuti E, Urban MW, Winter R, Larsson M. Plaque characterization using shear wave elastography—evaluation of differentiability and accuracy using a combined ex vivo and in vitro setup. ACTA ACUST UNITED AC 2018; 63:235008. [DOI: 10.1088/1361-6560/aaec2b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
8
|
Guo M, Cai Y, Yao X, Li Z. Mathematical modeling of atherosclerotic plaque destabilization: Role of neovascularization and intraplaque hemorrhage. J Theor Biol 2018; 450:53-65. [PMID: 29704490 DOI: 10.1016/j.jtbi.2018.04.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 03/29/2018] [Accepted: 04/23/2018] [Indexed: 01/03/2023]
Abstract
Observational studies have identified angiogenesis from the adventitial vasa vasorum and intraplaque hemorrhage (IPH) as critical factors in atherosclerotic plaque progression and destabilization. Here we propose a mathematical model incorporating intraplaque neovascularization and hemodynamic calculation with plaque destabilization for the quantitative evaluation of the role of neoangiogenesis and IPH in the vulnerable atherosclerotic plaque formation. An angiogenic microvasculature is generated by two-dimensional nine-point discretization of endothelial cell proliferation and migration from the vasa vasorum. Three key cells (endothelial cells, smooth muscle cells and macrophages) and three key chemicals (vascular endothelial growth factors, extracellular matrix and matrix metalloproteinase) are involved in the plaque progression model, and described by the reaction-diffusion partial differential equations. The hemodynamic calculation of the microcirculation on the generated microvessel network is carried out by coupling the intravascular, interstitial and transvascular flow. The plasma concentration in the interstitial domain is defined as the description of IPH area according to the diffusion and convection with the interstitial fluid flow, as well as the extravascular movement across the leaky vessel wall. The simulation results demonstrate a series of pathophysiological phenomena during the vulnerable progression of an atherosclerotic plaque, including the expanding necrotic core, the exacerbated inflammation, the high microvessel density (MVD) region at the shoulder areas, the transvascular flow through the capillary wall and the IPH. The important role of IPH in the plaque destabilization is evidenced by simulations with varied model parameters. It is found that the IPH can significantly speed up the plaque vulnerability by increasing necrotic core and thinning fibrous cap. In addition, the decreased MVD and vessel permeability may slow down the process of plaque destabilization by reducing the IPH dramatically. We envision that the present model and its future advances can serve as a valuable theoretical platform for studying the dynamic changes in the microenvironment during the plaque destabilization.
Collapse
Affiliation(s)
- Muyi Guo
- School of Biological Sciences and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Yan Cai
- School of Biological Sciences and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Xinke Yao
- School of Biological Sciences and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Zhiyong Li
- School of Biological Sciences and Medical Engineering, Southeast University, Nanjing 210096, China; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4001, Australia.
| |
Collapse
|
9
|
Shih CC, Chen PY, Ma T, Zhou Q, Shung KK, Huang CC. Development of an intravascular ultrasound elastography based on a dual-element transducer. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180138. [PMID: 29765694 PMCID: PMC5936959 DOI: 10.1098/rsos.180138] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/12/2018] [Indexed: 06/03/2023]
Abstract
The ability to measure the elastic properties of plaques and vessels would be useful in clinical diagnoses, particularly for detecting a vulnerable plaque. This study demonstrates the feasibility of the combination of intravascular ultrasound (IVUS) and acoustic radiation force elasticity imaging for detecting the distribution of stiffness within atherosclerotic arteries ex vivo. A dual-frequency IVUS transducer with two elements was used to induce the propagation of the shear wave (by the 8.5 MHz pushing element) which could be simultaneously monitored by the 31 MHz imaging element. The wave-amplitude image and the wave-velocity image were reconstructed by measuring the peak displacement and wave velocity of shear wave propagation, respectively. System performance was verified using gelatin phantoms. The phantom results demonstrate that the stiffness differences of shear modulus of 1.6 kPa can be distinguished through the wave-amplitude and wave-velocity images. The stiffness distributions of the atherosclerotic aorta from a rabbit were obtained, for which the values of peak displacement and the shear wave velocity were 3.7 ± 1.2 µm and 0.38 ± 0.19 m s-1 for the lipid-rich plaques, and 1.0 ± 0.2 µm and 3.45 ± 0.45 m s-1 for the arterial walls, respectively. These results indicate that IVUS elasticity imaging can be used to distinguish the elastic properties of plaques and vessels.
Collapse
Affiliation(s)
- Cho-Chiang Shih
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Pei-Yu Chen
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Teng Ma
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Qifa Zhou
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - K. Kirk Shung
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Chih-Chung Huang
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
| |
Collapse
|
10
|
de Korte CL, Fekkes S, Nederveen AJ, Manniesing R, Hansen HRHG. Review: Mechanical Characterization of Carotid Arteries and Atherosclerotic Plaques. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2016; 63:1613-1623. [PMID: 27249826 DOI: 10.1109/tuffc.2016.2572260] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Cardiovascular disease (CVD) is a leading cause of death and is in the majority of cases due to the formation of atherosclerotic plaques in arteries. Initially, thickening of the inner layer of the arterial wall occurs. Continuation of this process leads to plaque formation. The risk of a plaque to rupture and thus to induce an ischemic event is directly related to its composition. Consequently, characterization of the plaque composition and its proneness to rupture are of crucial importance for risk assessment and treatment strategies. The carotid is an excellent artery to be imaged with ultrasound because of its superficial position. In this review, ultrasound-based methods for characterizing the mechanical properties of the carotid wall and atherosclerotic plaque are discussed. Using conventional echography, the intima media thickness (IMT) can be quantified. There is a wealth of studies describing the relation between IMT and the risk for myocardial infarction and stroke. Also the carotid distensibility can be quantified with ultrasound, providing a surrogate marker for the cross-sectional mechanical properties. Although all these parameters are associated with CVD, they do not easily translate to individual patient risk. Another technique is pulse wave velocity (PWV) assessment, which measures the propagation of the pressure pulse over the arterial bed. PWV has proven to be a marker for global arterial stiffness. Recently, an ultrasound-based method to estimate the local PWV has been introduced, but the clinical effectiveness still needs to be established. Other techniques focus on characterization of plaques. With ultrasound elastography, the strain in the plaque due to the pulsatile pressure can be quantified. This technique was initially developed using intravascular catheters to image coronaries, but recently noninvasive methods were successfully developed. A high correlation between the measured strain and the risk for rupture was established. Acoustic radiation force impulse (ARFI) imaging also provides characterization of local plaque components based on mechanical properties. However, both elastography and ARFI provide an indirect measure of the elastic modulus of tissue. With shear wave imaging, the elastic modulus can be quantified, although the carotid artery is one of the most challenging tissues for this technique due to its size and geometry. Prospective studies still have to establish the predictive value of these techniques for the individual patient. Validation of ultrasound-based mechanical characterization of arteries and plaques remains challenging. Magnetic resonance imaging is often used as the "gold" standard for plaque characterization, but its limited resolution renders only global characterization of the plaque. CT provides information on the vascular tree, the degree of stenosis, and the presence of calcified plaque, while soft plaque characterization remains limited. Histology still is the gold standard, but is available only if tissue is excised. In conclusion, elastographic ultrasound techniques are well suited to characterize the different stages of vascular disease.
Collapse
|
11
|
Widman E, Maksuti E, Amador C, Urban MW, Caidahl K, Larsson M. Shear Wave Elastography Quantifies Stiffness in Ex Vivo Porcine Artery with Stiffened Arterial Region. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:2423-2435. [PMID: 27425151 DOI: 10.1016/j.ultrasmedbio.2016.05.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 05/17/2016] [Accepted: 05/31/2016] [Indexed: 06/06/2023]
Abstract
Five small porcine aortas were used as a human carotid artery model, and their stiffness was estimated using shear wave elastography (SWE) in the arterial wall and a stiffened artery region mimicking a stiff plaque. To optimize the SWE settings, shear wave bandwidth was measured with respect to acoustic radiation force push length and number of compounded angles used for motion detection with plane wave imaging. The mean arterial wall and simulated plaque shear moduli varied from 41 ± 5 to 97 ± 10 kPa and from 86 ± 13 to 174 ± 35 kPa, respectively, over the pressure range 20-120 mmHg. The results revealed that a minimum bandwidth of approximately 1500 Hz is necessary for consistent shear modulus estimates, and a high pulse repetition frequency using no image compounding is more important than a lower pulse repetition frequency with better image quality when estimating arterial wall and plaque stiffness using SWE.
Collapse
Affiliation(s)
- Erik Widman
- Department of Medical Engineering, School of Technology and Health, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden.
| | - Elira Maksuti
- Department of Medical Engineering, School of Technology and Health, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden
| | - Carolina Amador
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Matthew W Urban
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA; Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Kenneth Caidahl
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden
| | - Matilda Larsson
- Department of Medical Engineering, School of Technology and Health, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden
| |
Collapse
|
12
|
Czernuszewicz TJ, Gallippi CM. On the Feasibility of Quantifying Fibrous Cap Thickness With Acoustic Radiation Force Impulse (ARFI) Ultrasound. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2016; 63:1262-75. [PMID: 26955026 PMCID: PMC5084842 DOI: 10.1109/tuffc.2016.2535440] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Acute cerebrovascular accidents are associated with the rupture of vulnerable atherosclerotic plaques in the carotid arteries. Fibrous cap (FC) thickness has been shown to be an important predictor of plaque rupture but has been challenging to measure accurately with clinical noninvasive imaging modalities. The goals of this investigation were first, to evaluate the feasibility of using transcutaneous acoustic radiation force impulse (ARFI) ultrasound to quantify FC thickness and second, to optimize both imaging and motion-tracking parameters to support such measurements. FCs with varying thickness (0.1-1.0 mm) were simulated using a simple-layered geometry, and their mechanical response to an impulse of radiation force was solved using finite-element method (FEM) modeling. Ultrasound tracking of FEM displacements was performed in Field II utilizing three center frequencies (6, 9, and 12 MHz) and eight motion-tracking kernel lengths ( 0.5λ-4λ). Additionally, FC thickness in two carotid plaques imaged in vivo was measured with ARFI and compared to matched histology. The results of this study demonstrate that 1) tracking pulse frequencies around 12 MHz are necessary to resolve caps around 0.2 mm; 2) large motion-tracking kernel sizes introduce bias into thickness measurements and overestimate the true cap thickness; and 3) color saturation settings on ARFI peak displacement images can impact thickness measurement accuracy substantially.
Collapse
Affiliation(s)
- Tomasz J. Czernuszewicz
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC, USA
| | - Caterina M. Gallippi
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC, USA. Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC, USA
| |
Collapse
|
13
|
Shih CC, Lai TY, Huang CC. Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results. ULTRASONICS 2016; 70:64-74. [PMID: 27135187 DOI: 10.1016/j.ultras.2016.04.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 04/18/2016] [Accepted: 04/19/2016] [Indexed: 05/13/2023]
Abstract
The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI-IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm(2), as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm(2) was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI-IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the experimental results reported herein can be applied in ARFI-IVUS imaging applications.
Collapse
Affiliation(s)
- Cho-Chiang Shih
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Ting-Yu Lai
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Chih-Chung Huang
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan.
| |
Collapse
|
14
|
Wang X, Mitchell CC, Varghese T, Jackson DC, Rocque BG, Hermann BP, Dempsey RJ. Improved Correlation of Strain Indices with Cognitive Dysfunction with Inclusion of Adventitial Layer with Carotid Plaque. ULTRASONIC IMAGING 2016; 38:194-208. [PMID: 26025578 PMCID: PMC4662918 DOI: 10.1177/0161734615589252] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Plaque instability may lead to chronic embolization, which in turn may contribute to progressive cognitive decline. Accumulated strain tensor indices over a cardiac cycle within a pulsating carotid plaque may be viable biomarkers for the diagnosis of plaque instability. Using plaque-only carotid artery segmentations, we recently demonstrated that impaired cognitive function correlated significantly with maximum axial and lateral strain indices within a localized region of interest in plaque. Inclusion of the adventitial layer focuses our strain or instability measures on the vessel wall-plaque interface hypothesized to be a region with increased shearing forces and measureable instability. A hierarchical block-matching motion tracking algorithm developed in our laboratory was used to estimate accumulated axial, lateral, and shear strain distribution in plaques identified with the plaque-with-adventitia segmentation. Correlations of strain indices to the Repeatable Battery for the Assessment of Neuropsychological Status Total score were performed and compared with previous results. Overall, correlation coefficients (r) and significance (p) values improved for axial, lateral, and shear strain indices. Shear strain indices, however, demonstrated the largest improvement. The Pearson correlation coefficients for maximum shear strain and cognition improved from the previous plaque-only analyses of -0.432 and -0.345 to -0.795 and -0.717 with the plaque-with-adventitia segmentation for the symptomatic group and for all patients combined, respectively. Our results demonstrate the advantage of including adventitia for ultrasound carotid strain imaging providing improved association to parameters assessing cognitive impairment in patients. This supports theories of the importance of the vessel wall plaque interface in the pathophysiology of embolic disease.
Collapse
Affiliation(s)
- X Wang
- Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| | - C C Mitchell
- Department of Medicine, University of Wisconsin-Madison, Madison School of Medicine and Public Health, WI, USA
| | - T Varghese
- Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| | - D C Jackson
- Department of Neurology, University of Wisconsin-Madison, Madison School of Medicine and Public Health, WI, USA
| | - B G Rocque
- Department of Neurological Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| | - B P Hermann
- Department of Neurology, University of Wisconsin-Madison, Madison School of Medicine and Public Health, WI, USA
| | - R J Dempsey
- Department of Neurological Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| |
Collapse
|
15
|
The simulation of magnetic resonance elastography through atherosclerosis. J Biomech 2016; 49:1781-1788. [PMID: 27130475 DOI: 10.1016/j.jbiomech.2016.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 04/07/2016] [Accepted: 04/09/2016] [Indexed: 11/23/2022]
Abstract
The clinical diagnosis of atherosclerosis via the measurement of stenosis size is widely acknowledged as an imperfect criterion. The vulnerability of an atherosclerotic plaque to rupture is associated with its mechanical properties. The potential to image these mechanical properties using magnetic resonance elastography (MRE) was investigated through synthetic datasets. An image of the steady state wave propagation, equivalent to the first harmonic, can be extracted directly from finite element analysis. Inversion of this displacement data yields a map of the shear modulus, known as an elastogram. The variation of plaque composition, stenosis size, Gaussian noise, filter thresholds and excitation frequency were explored. A decreasing mean shear modulus with an increasing lipid composition was identified through all stenosis sizes. However the inversion algorithm showed sensitivity to parameter variation leading to artefacts which disrupted both the elastograms and quantitative trends. As noise was increased up to a realistic level, the contrast was maintained between the fully fibrous and lipid plaques but lost between the interim compositions. Although incorporating a Butterworth filter improved the performance of the algorithm, restrictive filter thresholds resulted in a reduction of the sensitivity of the algorithm to composition and noise variation. Increasing the excitation frequency improved the techniques ability to image the magnitude of the shear modulus and identify a contrast between compositions. In conclusion, whilst the technique has the potential to image the shear modulus of atherosclerotic plaques, future research will require the integration of a heterogeneous inversion algorithm.
Collapse
|
16
|
Doherty JR, Dahl JJ, Kranz PG, El Husseini N, Chang HC, Chen NK, Allen JD, Ham KL, Trahey GE. Comparison of Acoustic Radiation Force Impulse Imaging Derived Carotid Plaque Stiffness With Spatially Registered MRI Determined Composition. IEEE TRANSACTIONS ON MEDICAL IMAGING 2015; 34:2354-65. [PMID: 25974933 PMCID: PMC4678151 DOI: 10.1109/tmi.2015.2432797] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Measurements of plaque stiffness may provide important prognostic and diagnostic information to help clinicians distinguish vulnerable plaques containing soft lipid pools from more stable, stiffer plaques. In this preliminary study, we compare in vivo ultrasonic Acoustic Radiation Force Impulse (ARFI) imaging derived measures of carotid plaque stiffness with composition determined by spatially registered Magnetic Resonance Imaging (MRI) in five human subjects with stenosis > 50%. Ultrasound imaging was implemented on a commercial diagnostic scanner with custom pulse sequences to collect spatially registered 2D longitudinal B-mode and ARFI images. A standardized, multi-contrast weighted MRI sequence was used to obtain 3D Time of Flight (TOF), T1 weighted (T1W), T2 weighted (T2W), and Proton Density Weighted (PDW) transverse image stacks of volumetric data. The MRI data was segmented to identify lipid, calcium, and normal loose matrix components using commercially available software. 3D MRI segmented plaque models were rendered and spatially registered with 2D B-mode images to create fused ultrasound and MRI volumetric images for each subject. ARFI imaging displacements in regions of interest (ROIs) derived from MRI segmented contours of varying composition were compared. Regions of calcium and normal loose matrix components identified by MRI presented as homogeneously stiff regions of similarly low (typically ≈ 1 μm) displacement in ARFI imaging. MRI identified lipid pools > 2 mm(2), found in three out of five subjects, presented as softer regions of increased displacement that were on average 1.8 times greater than the displacements in adjacent regions of loose matrix components in spatially registered ARFI images. This work provides early evidence supporting the use of ARFI imaging to noninvasively identify lipid regions in carotid artery plaques in vivo that are believed to increase the propensity of a plaque to rupture. Additionally, the results provide early training data for future studies and aid in the interpretation and possible clinical utility of ARFI imaging for identifying the elusive vulnerable plaque.
Collapse
|
17
|
Widman E, Maksuti E, Larsson D, Urban MW, Bjällmark A, Larsson M. Shear wave elastography plaque characterization with mechanical testing validation: a phantom study. Phys Med Biol 2015; 60:3151-74. [PMID: 25803520 DOI: 10.1088/0031-9155/60/8/3151] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
|
18
|
Caenen A, Shcherbakova D, Verhegghe B, Papadacci C, Pernot M, Segers P, Swillens A. A versatile and experimentally validated finite element model to assess the accuracy of shear wave elastography in a bounded viscoelastic medium. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2015; 62:439-450. [PMID: 25768813 DOI: 10.1109/tuffc.2014.006682] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The feasibility of shear wave elastography (SWE) in arteries for cardiovascular risk assessment remains to be investigated as the artery's thin wall and intricate material properties induce complex shear wave (SW) propagation phenomena. To better understand the SW physics in bounded media, we proposed an in vitro validated finite element model capable of simulating SW propagation, with full flexibility at the level of the tissue's geometry, material properties, and acoustic radiation force. This computer model was presented in a relatively basic set-up, a homogeneous slab of gelatin-agar material (4.35 mm thick), allowing validation of the numerical settings according to actual SWE measurements. The resulting tissue velocity waveforms and SW propagation speed matched well with the measurement: 4.46 m/s (simulation) versus 4.63 ± 0.07 m/s (experiment). Further, we identified the impact of geometrical and material parameters on the SW propagation characteristics. As expected, phantom thickness was a determining factor of dispersion. Adding viscoelasticity to the model augmented the estimated wave speed to 4.58 m/s, an even better match with the experimental determined value. This study demonstrated that finite element modeling can be a powerful tool to gain insight into SWE mechanics and will in future work be advanced to more clinically relevant settings.
Collapse
|
19
|
Czernuszewicz TJ, Homeister JW, Caughey MC, Farber MA, Fulton JJ, Ford PF, Marston WA, Vallabhaneni R, Nichols TC, Gallippi CM. Non-invasive in vivo characterization of human carotid plaques with acoustic radiation force impulse ultrasound: comparison with histology after endarterectomy. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:685-97. [PMID: 25619778 PMCID: PMC4331250 DOI: 10.1016/j.ultrasmedbio.2014.09.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 08/30/2014] [Accepted: 09/10/2014] [Indexed: 05/03/2023]
Abstract
Ischemic stroke from thromboembolic sources is linked to carotid artery atherosclerotic disease with a trend toward medical management in asymptomatic patients. Extent of disease is currently diagnosed by non-invasive imaging techniques that measure luminal stenosis, but it has been suggested that a better biomarker for determining risk of future thromboembolic events is plaque morphology and composition. Specifically, plaques that are composed of mechanically soft lipid/necrotic regions covered by thin fibrous caps are the most vulnerable to rupture. An ultrasound technique that non-invasively interrogates the mechanical properties of soft tissue, called acoustic radiation force impulse (ARFI) imaging, has been developed as a new modality for atherosclerotic plaque characterization using phantoms and atherosclerotic pigs, but the technique has yet to be validated in vivo in humans. In this preliminary study, in vivo ARFI imaging is presented in a case study format for four patients undergoing clinically indicated carotid endarterectomy and compared with histology. In two type Va plaques, characterized by lipid/necrotic cores covered by fibrous caps, mean ARFI displacements in focal regions were high relative to the surrounding plaque material, suggesting soft features were covered by stiffer layers within the plaques. In two type Vb plaques, characterized by heavy calcification, mean ARFI peak displacements were low relative to the surrounding plaque and arterial wall, suggesting stiff tissue. This pilot study illustrates the feasibility and challenges of transcutaneous ARFI for characterizing the material and structural composition of carotid atherosclerotic plaques via mechanical properties, in humans, in vivo.
Collapse
Affiliation(s)
- Tomasz J Czernuszewicz
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, USA
| | - Jonathon W Homeister
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Melissa C Caughey
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Mark A Farber
- Department of Surgery, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Joseph J Fulton
- Department of Surgery, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Peter F Ford
- Department of Surgery, University of North Carolina, Chapel Hill, North Carolina, USA
| | - William A Marston
- Department of Surgery, University of North Carolina, Chapel Hill, North Carolina, USA
| | | | - Timothy C Nichols
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina, USA; Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Caterina M Gallippi
- McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA; Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, North Carolina, USA.
| |
Collapse
|
20
|
Brezinski ME. Practical Challenges of Current Video Rate OCT Elastography: Accounting for Dynamic and Static Tissue Properties. JOURNAL OF LASERS, OPTICS & PHOTONICS 2014; 1:112. [PMID: 29286052 PMCID: PMC5743221 DOI: 10.4172/2469-410x.1000112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Optical coherence tomography (OCT) elastography (OCTE) has the potential to be an important diagnostic tool for pathologies including coronary artery disease, osteoarthritis, malignancies, and even dental caries. Many groups have performed OCTE, including our own, using a wide range of approaches. However, we will demonstrate current OCTE approaches are not scalable to real-time, in vivo imaging. As will be discussed, among the most important reasons is current designs focus on the system and not the target. Specifically, tissue dynamic responses are not accounted, with examples being the tissue strain response time, preload variability, and conditioning variability. Tissue dynamic responses, and to a lesser degree static tissue properties, prevent accurate video rate modulus assessments for current embodiments. Accounting for them is the focus of this paper. A top-down approach will be presented to overcome these challenges to real time in vivo tissue characterization. Discussed first is an example clinical scenario where OTCE would be of substantial relevance, the prevention of acute myocardial infarction or heart attacks. Then the principles behind OCTE are examined. Next, constrains on in vivo application of current OCTE are evaluated, focusing on dynamic tissue responses. An example is the tissue strain response, where it takes about 20 msec after a stress is applied to reach plateau. This response delay is not an issue at slow acquisition rates, as most current OCTE approaches are preformed, but it is for video rate OCTE. Since at video rate each frame is only 30 msec, for essentially all current approaches this means the strain for a given stress is changing constantly during the B-scan. Therefore the modulus can't be accurately assessed. This serious issue is an even greater problem for pulsed techniques as it means the strain/modulus for a given stress (at a location) is unpredictably changing over a B-scan. The paper concludes by introducing a novel video rate approach to overcome these challenges.
Collapse
Affiliation(s)
- Mark E Brezinski
- Center for Optics and Modern Physics, Brigham and Women’s Hospital, 75 Francis Street, Boston, M.A. 02115, USA
- Harvard Medical School, 25 Shattuck Street, Boston, M.A. 02115, USA
- Department of Electrical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, M.A. 02139, USA
| |
Collapse
|
21
|
Doherty JR, Dahl JJ, Trahey GE. Harmonic tracking of acoustic radiation force-induced displacements. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2013; 60:2347-58. [PMID: 24158290 PMCID: PMC3974334 DOI: 10.1109/tuffc.2013.6644738] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Ultrasound-based elasticity imaging methods rely upon accurate estimates of tissue deformation to characterize the mechanical properties of soft tissues. These methods are corrupted by clutter, which can bias and/or increase variance in displacement estimates. Harmonic imaging methods are routinely used for clutter suppression and improved image quality in conventional B-mode ultrasound, but have not been utilized in ultrasound-based elasticity imaging methods. We introduce a novel, fully-sampled pulse-inversion harmonic method for tracking tissue displacements that corrects the loss in temporal sampling frequency associated with conventional pulse-inversion techniques. The method is implemented with acoustic radiation force impulse (ARFI) imaging to monitor the displacements induced by an impulsive acoustic radiation force excitation. Custom pulse sequences were implemented on a diagnostic ultrasound scanner to collect spatially-matched fundamental and harmonic information within a single acquisition. B-mode and ARFI images created from fundamental data collected at 4 MHz and 8 MHz are compared with 8-MHz harmonic images created using a band-pass filter approach and the fully sampled pulse-inversion method. In homogeneous, tissue-mimicking phantoms, where no visible clutter was observed, there was little difference in the axial displacements, estimated jitter, and normalized cross-correlation among the fundamental and harmonic tracking methods. The similarity of the lower- and higher-frequency methods suggests that any improvement resulting from the increased frequency of the harmonic components is negligible. The harmonic tracking methods demonstrated a marked improvement in B-mode and ARFI image quality of in vivo carotid arteries. Improved feature detection and decreased variance in estimated displacements were observed in the arterial walls of harmonic ARFI images, especially in the pulse-inversion harmonic ARFI images. Within the lumen, the harmonic tracking methods improved the discrimination of the blood–vessel interface, making it easier to visualize plaque boundaries. Improvements in harmonic ARFI images in vivo were consistent with suppressed clutter supported by improved contrast and contrast-to-noise ratio (CNR) in the matched harmonic B-mode images compared with the fundamental B-mode images. These results suggest that harmonic tracking methods can improve the clinical utility and diagnostic accuracy of ultrasound-based elasticity imaging methods.
Collapse
|
22
|
Doherty JR, Trahey GE, Nightingale KR, Palmeri ML. Acoustic radiation force elasticity imaging in diagnostic ultrasound. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2013; 60:685-701. [PMID: 23549529 PMCID: PMC3679553 DOI: 10.1109/tuffc.2013.2617] [Citation(s) in RCA: 169] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo; elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed noninvasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods.
Collapse
Affiliation(s)
- Joshua R Doherty
- Department of Biomedical Engineering, Duke University, Durham, NC, USA.
| | | | | | | |
Collapse
|