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Shajudeen P, Tang S, Chaudhry A, Kim N, Reddy JN, Tasciotti E, Righetti R. Modeling and Analysis of Ultrasound Elastographic Axial Strains for Spine Fracture Identification. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:898-909. [PMID: 31796395 DOI: 10.1109/tuffc.2019.2956730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This study reports the first use of ultrasound (US) elastography for imaging spinal fractures by assessing the mechanical response of the soft tissue at the posterior vertebra boundary to a uniaxial compression in rabbit ex vivo samples. Three-dimensional finite-element (FE) models of the vertebra-soft tissue complex in rabbit samples are generated and analyzed to evaluate the distribution of the axial normal and shear strains at the vertebra-soft tissue interface. Experiments on the same samples are performed to corroborate simulation findings. Results of this study indicate that the distribution of the axial strains manifests as distinct patterns around intact and fractured vertebrae. Numerical characteristics of the axial strain's spatial distribution are further used to construct two shape descriptors to make inferences on spinal abnormalities: 1) axial normal strain asymmetry for assessing the presence of fractures and 2) principal orientation of axial shear strain concentration regions (shear zones) for measurement of spinous process dislocation. This study demonstrates that axial normal strain and axial shear strain maps obtained via US elastography can provide a new means to detect spine fractures and abnormalities in the selected ex vivo animal models. Spinal fracture detection is important for the assessment of spinal cord injuries and stability. However, identification of spinal fractures using US is currently challenging. Our results show that features resulting from strain elastograms can serve as a useful adjunct to B-mode images in identifying spine fractures in the selected animal samples, and this information could be helpful in clinical settings.
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Tang S, Sabonghy EP, Chaudhry A, Shajudeen PS, Islam MT, Kim N, Cabrera FJ, Reddy JN, Tasciotti E, Righetti R. A Model-Based Approach to Investigate the Effect of a Long Bone Fracture on Ultrasound Strain Elastography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:1178-1191. [PMID: 29994472 DOI: 10.1109/tmi.2018.2792437] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The mechanical behavior of long bones and fractures has been under investigation for many decades due to its complexity and clinical relevance. In this paper, we report a new subject-specific methodology to predict and analyze the mechanical behavior of the soft tissue at a bone interface with the intent of identifying the presence and location of bone abnormalities with high accuracy, spatial resolution, and contrast. The proposed methodology was tested on both intact and fractured rabbit femur samples with finite element-based 3-D simulations, created from actual femur computed tomography data, and ultrasound elastography experiments. The results included in this study demonstrate that elastographic strains at the bone/soft tissue interface can be used to differentiate fractured femurs from the intact ones on a distribution level. These results also demonstrate that coronal plane axial shear strain creates a unique contrast mechanism that can be used to reliably detect fractures (both complete and incomplete) in long bones. Kruskal-Wallis test further demonstrates that the contrast measure for the fracture group (simulation: 2.1286±0.2206; experiment: 2.7034 ± 1.0672) is significantly different from that for the intact group (simulation: 0 ± 0; experiment: 1.1540±0.6909) when using coronal plane axial shear strain elastography ( < 0.01). We conclude that: 1) elastography techniques can be used to accurately identify the presence and location of fractures in a long bone and 2) the proposed model-based approach can be used to predict and analyze strains at a bone fracture site and to better interpret experimental elastographic data.
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Tang S, Sabonghy EP, Chaudhry A, Shajudeen PS, Islam MT, Kim N, Cabrera FJ, Reddy JN, Tasciotti E, Righetti R. A Model-Based Approach to Investigate the Effect of a Long Bone Fracture on Ultrasound Strain Elastography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:2704-2717. [PMID: 29994472 DOI: 10.1109/tmi.2018.2849996] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The mechanical behavior of long bones and fractures has been under investigation for many decades due to its complexity and clinical relevance. In this paper, we report a new subject-specific methodology to predict and analyze the mechanical behavior of the soft tissue at a bone interface with the intent of identifying the presence and location of bone abnormalities with high accuracy, spatial resolution, and contrast. The proposed methodology was tested on both intact and fractured rabbit femur samples with finite element-based 3-D simulations, created from actual femur computed tomography data, and ultrasound elastography experiments. The results included in this study demonstrate that elastographic strains at the bone/soft tissue interface can be used to differentiate fractured femurs from the intact ones on a distribution level. These results also demonstrate that coronal plane axial shear strain creates a unique contrast mechanism that can be used to reliably detect fractures (both complete and incomplete) in long bones. Kruskal-Wallis test further demonstrates that the contrast measure for the fracture group (simulation: 2.1286±0.2206; experiment: 2.7034 ± 1.0672) is significantly different from that for the intact group (simulation: 0 ± 0; experiment: 1.1540±0.6909) when using coronal plane axial shear strain elastography ( < 0.01). We conclude that: 1) elastography techniques can be used to accurately identify the presence and location of fractures in a long bone and 2) the proposed model-based approach can be used to predict and analyze strains at a bone fracture site and to better interpret experimental elastographic data.
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Islam MT, Righetti R. A novel filter for accurate estimation of fluid pressure and fluid velocity using poroelastography. Comput Biol Med 2018; 101:90-99. [PMID: 30121497 DOI: 10.1016/j.compbiomed.2018.08.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/03/2018] [Accepted: 08/04/2018] [Indexed: 12/11/2022]
Abstract
Fluid pressure and fluid velocity carry important information for cancer diagnosis, prognosis and treatment. Recent work has demonstrated that estimation of these parameters is theoretically possible using ultrasound poroelastography. However, accurate estimation of these parameters requires high quality axial and lateral strain estimates from noisy ultrasound radio frequency (RF) data. In this paper, we propose a filtering technique combining two efficient filters for removal of noise from strain images, i.e., Kalman and nonlinear complex diffusion filters (NCDF). Our proposed filter is based on a novel noise model, which takes into consideration both additive and amplitude modulation noise in the estimated strains. Using finite element and ultrasound simulations, we demonstrate that the proposed filtering technique can significantly improve image quality of lateral strain elastograms along with fluid pressure and velocity elastograms. Technical feasibility of the proposed method on an in vivo set of data is also demonstrated. Our results show that the CNRe of the lateral strain, fluid pressure and fluid velocity as estimated using the proposed technique is higher by at least 10.9%, 51.3% and 334.4% when compared to the results obtained using a Kalman filter only, by at least 8.9%, 27.6% and 219.5% when compared to the results obtained using a NCDF only and by at least 152.3%, 1278% and 742% when compared to the results obtained using a median filter only for all SNRs considered in this study.
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Affiliation(s)
- Md Tauhidul Islam
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, 77840, Texas, USA
| | - Raffaella Righetti
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, 77840, Texas, USA.
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Islam MT, Reddy JN, Righetti R. An analytical poroelastic model of a non-homogeneous medium under creep compression for ultrasound poroelastography applications - Part II. J Biomech Eng 2018; 141:2686531. [PMID: 30029209 DOI: 10.1115/1.4040604] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Indexed: 11/08/2022]
Abstract
An analytical theory for the unconfined creep behavior of a cylindrical inclusion (simulating a soft tissue tumor) embedded in a cylindrical background sample (simulating normal tissue) is presented and analyzed in this paper. Both the inclusion and the background are considered as fluid-filled, porous materials, each of them being characterized by a set of mechanical parameters. Specifically, in this derivation, the inclusion is assumed to have significantly higher interstitial permeability than the background. The formulations of the effective Poisson's ratio (EPR) and fluid pressure in the inclusion and in the background are derived for the case of a sample subjected to a creep compression. The developed analytical expressions are validated using finite element models (FEM). Statistical comparison between the results obtained from the developed model and the results from FEM demonstrates accuracy of the proposed theoretical model higher than 99.4%. The model presented in this paper complements the one reported in the companion paper (Part I), which refers to the case of an inclusion having less interstitial permeability than the background.
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Affiliation(s)
- Md Tauhidul Islam
- Graduate Research Assistant, Ultrasound and Elasticity Imaging Laboratory, Department of Electrical & Computer Engineering, Texas A&M University, College Station, Texas, USA-77840
| | - J N Reddy
- Professor, Department of Mechanical Engineering, Texas A&M University, College Station, Texas, USA-77840
| | - Raffaella Righetti
- Associate Professor, Department of Electrical & Computer Engineering, Texas A&M University, College Station, Texas, USA-77840
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Islam MT, Chaudhry A, Unnikrishnan G, Reddy JN, Righetti R. An analytical poroelastic model for ultrasound elastography imaging of tumors. ACTA ACUST UNITED AC 2018; 63:025031. [DOI: 10.1088/1361-6560/aa9631] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Tang S, Chaudhry A, Kim N, Reddy JN, Righetti R. Effect of bone-soft tissue friction on ultrasound axial shear strain elastography. Phys Med Biol 2017; 62:6074-6091. [PMID: 28699617 DOI: 10.1088/1361-6560/aa766f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bone-soft tissue friction is an important factor affecting several musculoskeletal disorders, frictional syndromes and the ability of a bone fracture to heal. However, this parameter is difficult to determine using non-invasive imaging modalities, especially in clinical settings. Ultrasound axial shear strain elastography is a non-invasive imaging modality that has been used in the recent past to estimate the bonding between different tissue layers. As most elastography methods, axial shear strain elastography is primarily used in soft tissues. More recently, this technique has been proposed to assess the bone-soft tissue interface. In this paper, we investigate the effect of a variation in bone-soft tissue friction coefficient in the resulting axial shear strain elastograms. Finite element poroelastic models of bone specimens exhibiting different bone-soft tissue friction coefficients were created and mechanically analyzed. These models were then imported to an ultrasound elastography simulation module to assess the presence of axial shear strain patterns. In vitro experiments were performed to corroborate selected simulation results. The results of this study show that the normalized axial shear strain estimated at the bone-soft tissue interface is statistically correlated to the bone-soft tissue coefficient of friction. This information may prove useful to better interpret ultrasound elastography results obtained in bone-related applications and, possibly, monitor bone healing.
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Affiliation(s)
- Songyuan Tang
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States of America
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Chaudhry A, Kim N, Unnikrishnan G, Nair S, Reddy JN, Righetti R. Effect of Interstitial Fluid Pressure on Ultrasound Axial Strain and Axial Shear Strain Elastography. ULTRASONIC IMAGING 2017; 39:137-146. [PMID: 27694129 DOI: 10.1177/0161734616671713] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Ultrasound elastography is an imaging modality that has been used to diagnose tumors of the breast, thyroid, and prostate. Both axial strain elastography and axial shear strain elastography (ASSE) have shown significant potentials to differentiate between benign and malignant tumors. Elevated interstitial fluid pressure (IFP) is a characteristic of many malignant tumors and a major barrier in targeted drug delivery therapies. This parameter, however, has not received significant attention in ultrasound elastography and, in general, in most diagnostic imaging modalities yet. In this paper, we investigate the effect of an underlying IFP contrast on ultrasound axial strain and axial shear strain imaging using finite element analysis. Our results show that an underlying contrast in IFP creates a new contrast mechanism in both the axial strain and axial shear strain elastographic images. This information might be important for a better interpretation of elastographic images of tumors.
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Affiliation(s)
- Anuj Chaudhry
- 1 Department of Electrical & Computer Engineering, Texas A&M University, College Station, TX, USA
| | - Namhee Kim
- 2 Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
| | - Ginu Unnikrishnan
- 2 Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
| | - Sanjay Nair
- 1 Department of Electrical & Computer Engineering, Texas A&M University, College Station, TX, USA
| | - J N Reddy
- 2 Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
| | - Raffaella Righetti
- 1 Department of Electrical & Computer Engineering, Texas A&M University, College Station, TX, USA
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Galaz BA, Acevedo RH. Optimization of a Pixel-to-Pixel Curve-Fitting Method for Poroelastography Imaging. ULTRASOUND IN MEDICINE & BIOLOGY 2017; 43:309-322. [PMID: 27765386 DOI: 10.1016/j.ultrasmedbio.2016.09.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 08/31/2016] [Accepted: 09/06/2016] [Indexed: 06/06/2023]
Abstract
Ultrasound poroelastography is an imaging modality used to characterize the temporal behavior of soft tissue that can be modeled as a solid permeated by interconnected pores filled with liquid (poroelastic medium). It could be useful in the stage classification of lymphedema. Generally, time-constant models are applied to strain images, and precision of the fitting process, computational cost and versatility in response to changes in tissues properties are crucial aspects of clinical applications. In the work described here, we performed creep experiments on poroelastic phantoms and used rheologic models to visualize the changes in viscoelastic response associated with fluid mobility. We used the Levenberg-Marquardt algorithm as a fitting tool and performed parametric studies to improve its performance. On the basis of these studies, we proposed an optimization schema for the pixel-to-pixel curve-fitting process. We determined that the bimodal Kelvin-Voigt model describes efficiently the temporal evolution of the strain images in heterogeneous phantoms.
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Chaudhry A, Yazdi IK, Kongari R, Tasciotti E, Righetti R. A New Class of Phantom Materials for Poroelastography Imaging Techniques. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:1230-8. [PMID: 26806439 DOI: 10.1016/j.ultrasmedbio.2015.12.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/17/2015] [Accepted: 12/14/2015] [Indexed: 05/20/2023]
Abstract
Poroelastography is an elastographic technique used to image the temporal mechanical behavior of tissues. One of the major challenges in determining experimental potentials and limitations of this technique has been the lack of complex and realistic controlled phantoms that could be used to corroborate the limited number of theoretical and simulation studies available in the literature as well as to predict its performance in complex experimental situations and in a variety of conditions. In the study described here, we propose and analyze a new class of phantom materials for temporal elastography imaging. The results indicate that, by using polyacrylamide, we can generate inhomogeneous elastographic phantoms with controlled fluid content and fluid flow properties, while maintaining mechanical and ultrasonic properties similar to those of soft tissues.
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Affiliation(s)
- Anuj Chaudhry
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA
| | - Iman K Yazdi
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, Texas, USA; Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Rohit Kongari
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Ennio Tasciotti
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, Texas, USA
| | - Raffaella Righetti
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA.
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Nair SP, Righetti R. Resimulation of noise: a precision estimator for least square error curve-fitting tested for axial strain time constant imaging. Phys Med Biol 2015; 60:3515-29. [DOI: 10.1088/0031-9155/60/9/3515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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