The Experts below are selected from a list of 33084 Experts worldwide ranked by ideXlab platform
Tomy Varghese - One of the best experts on this subject based on the ideXlab platform.
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Cardiac Strain Imaging with Dynamically Skipped Frames: A Simulation Study
2020 IEEE International Ultrasonics Symposium (IUS), 2020Co-Authors: Rashid Al Mukaddim, Tomy VargheseAbstract:Accurate lateral displacement estimation is a critical requirement to reliably use cardiac Strain Imaging for myocardial health or carotid Strain Imaging to assess atherosclerosis. Estimation of small lateral displacements are challenging even with 2-D kernels. We investigate the feasibility of using a dynamic frame skip (DFS) approach to improve lateral Strain estimation for cardiac and carotid Strain Imaging. DFS automatically determines the optimal frame skip using axial Strain information estimated during displacement tracking. We incorporated DFS into a hierarchical Bayesian regularization based displacement tracking method for cardiac and carotid Strain Imaging. A finite element analysis (FEA) model of canine cardiac deformation was utilized to quantify estimation performance with DFS and compare against conventional inter-frame displacement (CFS) approach. DFS displacement and Strain temporal curves showed improved qualitative agreement with FEA ground truth compared to CFS results. Consequently, DFS had lower Strain total temporal relative (TTR) Strain errors (TTRaxial= 18.37 %, TTRlateral= 29.91 %, TTRradial = 17.32 %, and TTRlongitudinal = 14.51 %) compared to CFS (TTRaxial= 22.39 %, TTRlateral = 30.88 %, TTRradial = 22.35 %, and TTRlongitudinal= 15.87 %). These results show that DFS can potentially improve cardiac Strain estimation quality.
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A Novel Saline Infusion Sonohysterography-Based Strain Imaging Approach for Evaluation of Uterine Abnormalities In Vivo Preliminary Results
Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine, 2012Co-Authors: Eenas A Omari, Tomy Varghese, Mark A. KliewerAbstract:In this article, we demonstrate the feasibility of saline infusion sonohysterography-based Strain Imaging for the determination of stiffness variations in uterine masses in vivo. Strain images are estimated using a 2-dimensional multilevel hybrid algorithm developed for sector array ultrasound transducers. Coarse displacements are initially estimated using envelope echo signals, followed by a guided finer displacement estimation using window lengths on the order of 6 wavelengths and 7 A-lines on radiofrequency data. Strain images are obtained by estimating displacement slopes using least squares estimation. In this prospective study, we show that stiffer masses such as fibroids appear darker or as regions with low Strain on Strain images and are thus clearly differentiated when compared to normal uterine tissue. A high Strain boundary around stiffer masses referred to as a “halo” due to increased slipping or sliding of the mass during the applied deformation is also visualized. Uterine polyps, on the other hand, are visualized as masses that are brighter or regions with high Strain when compared to the background myometrium, indicating the presence of a softer mass. Axial Strain images provide additional new information that may supplement current clinical B-mode Imaging used for the diagnosis of uterine abnormalities. Our results show the feasibility of improving clinical diagnosis based on Strain Imaging.
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Bayesian Regularization Applied to Ultrasound Strain Imaging
IEEE transactions on bio-medical engineering, 2011Co-Authors: Matt Mccormick, Nicholas Rubert, Tomy VargheseAbstract:Noise artifacts due to signal decorrelation and reverberation are a considerable problem in ultrasound Strain Imaging. For block-matching methods, information from neighboring matching blocks has been utilized to regularize the estimated displacements. We apply a recursive Bayesian regularization algorithm developed by Hayton et al. [Artif. Intell., vol. 114, pp. 125-156, 1999] to phase-sensitive ultrasound RF signals to improve displacement estimation. The parameter of regularization is reformulated, and its meaning examined in the context of Strain Imaging. Tissue-mimicking experimental phantoms and RF data incorporating finite-element models for the tissue deformation and frequency-domain ultrasound simulations are used to compute the optimal parameter with respect to nominal Strain and algorithmic iterations. The optimal Strain regularization parameter was found to be twice the nominal Strain and did not vary significantly with algorithmic iterations. The technique demonstrates superior performance over median filtering in noise reduction at Strains 5% and higher for all quantitative experiments performed. For example, the Strain SNR was 11 dB higher than that obtained using a median filter at 7% Strain. It has to be noted that for applied deformations lower than 1%, since signal decorrelation errors are minimal, using this approach may degrade the displacement image.
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axial shear Strain Imaging for differentiating benign and malignant breast masses
Ultrasound in Medicine and Biology, 2010Co-Authors: Min Rao, Tomy Varghese, Timothy J Hall, Gale A Sisney, Sara Baker, Amy M Sommer, Elizabeth S BurnsideAbstract:Axial Strain Imaging has been utilized for the characterization of breast masses for over a decade; however, another important feature namely the shear Strain distribution around breast masses has only recently been used. In this article, we examine the feasibility of utilizing in vivo axial-shear Strain Imaging for differentiating benign from malignant breast masses. Radio-frequency data was acquired using a VFX 13-5 linear array transducer on 41 patients using a Siemens SONOLINE Antares real-time clinical scanner at the University of Wisconsin Breast Cancer Center. Free-hand palpation using deformations of up to 10% was utilized to generate axial Strain and axial-shear Strain images using a two-dimensional cross-correlation algorithm from the radio-frequency data loops. Axial-shear Strain areas normalized to the lesion size, applied Strain and lesion Strain contrast was utilized as a feature for differentiating benign from malignant masses. The normalized axial-shear Strain area feature estimated on eight patients with malignant tumors and 33 patients with fibroadenomas was utilized to demonstrate its potential for lesion differentiation. Biopsy results were considered the diagnostic standard for comparison. Our results indicate that the normalized axial-shear Strain area is significantly larger for malignant tumors compared with benign masses such as fibroadenomas. Axial-shear Strain pixel values greater than a specified threshold, including only those with correlation coefficient values greater than 0.75, were overlaid on the corresponding B-mode image to aid in diagnosis. A scatter plot of the normalized area feature demonstrates the feasibility of developing a linear classifier to differentiate benign from malignant masses. The area under the receiver operator characteristic curve utilizing the normalized axial-shear Strain area feature was 0.996, demonstrating the potential of this feature to noninvasively differentiate between benign and malignant breast masses.
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TU‐E‐201C‐05: Electrode Displacement Strain Imaging for Monitoring In‐Vivo Ablative Therapies
Medical Physics, 2010Co-Authors: Nicholas Rubert, Jingfeng Jiang, James A. Zagzebski, Shyam Bharat, Ryan J. Dewall, Anita Andreano, Christopher L. Brace, Lisa A. Sampson, Fred T. Lee, Tomy VargheseAbstract:Purpose: Percutaneous RF ablation is evolving into an accepted minimally‐invasive treatment for hepatic tumors. Monitoring and delineating the treated region is essential for its success. Ultrasoundelastography can become a convenient and cost‐effective means to delineate thermal lesion boundaries. This study assesses electrode displacement based Strain Imaging for monitoring abdominal RF ablation procedures that are difficult to monitor with conventional elastography Method and Materials: Thirteen RFablated regions were created in‐vivo in pig liver.Radiofrequency echo signal data for Strain Imaging were acquired using a Siemens Antares clinical scanner immediately following RF ablation procedures. Small displacements were applied to the unconStrained end of the ablationelectrode in‐vivo, resulting in localized tissue deformation. Strain images were then compared to gross‐pathology images of the same lesion along the two‐dimensional Imaging plane. Gross‐pathology images were obtained by fixing the excised thermal lesion and slicing though the lesion, utilizing marks on the liver surface denoting the Imaging plane and visual inspection of the electrode track. Results: Cross‐sectional area measurements of the thermal lesion obtained from the Strain images were derived using both manual and automated segmentation. Areas were compared with cross‐sectional area measurements from gross pathology images. Area measurements from Strain images were highly correlated to areas measured on gross‐pathology, where the linear correlation coefficients were R = 0.894, P < 0.001 and R = 0.828, P < 0.001, for the manual and automated segmentation, respectively. Conclusions:Electrode displacement based Strain Imaging provides high contrast between ablated and normal liver tissue, allowing for clear delineation of the thermal ablation zone. This complements clinical ultrasound Imaging, the preferred modality for real‐time guidance for the placement of the RF needle into the tumor, allowing multiple Imaging tasks to be performed with a single ultrasound machine. Supported by NIH‐NCI grants R01CA112192‐03 and R01CA112192‐S103.
Timothy J Hall - One of the best experts on this subject based on the ideXlab platform.
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axial shear Strain Imaging for differentiating benign and malignant breast masses
Ultrasound in Medicine and Biology, 2010Co-Authors: Min Rao, Tomy Varghese, Timothy J Hall, Gale A Sisney, Sara Baker, Amy M Sommer, Elizabeth S BurnsideAbstract:Axial Strain Imaging has been utilized for the characterization of breast masses for over a decade; however, another important feature namely the shear Strain distribution around breast masses has only recently been used. In this article, we examine the feasibility of utilizing in vivo axial-shear Strain Imaging for differentiating benign from malignant breast masses. Radio-frequency data was acquired using a VFX 13-5 linear array transducer on 41 patients using a Siemens SONOLINE Antares real-time clinical scanner at the University of Wisconsin Breast Cancer Center. Free-hand palpation using deformations of up to 10% was utilized to generate axial Strain and axial-shear Strain images using a two-dimensional cross-correlation algorithm from the radio-frequency data loops. Axial-shear Strain areas normalized to the lesion size, applied Strain and lesion Strain contrast was utilized as a feature for differentiating benign from malignant masses. The normalized axial-shear Strain area feature estimated on eight patients with malignant tumors and 33 patients with fibroadenomas was utilized to demonstrate its potential for lesion differentiation. Biopsy results were considered the diagnostic standard for comparison. Our results indicate that the normalized axial-shear Strain area is significantly larger for malignant tumors compared with benign masses such as fibroadenomas. Axial-shear Strain pixel values greater than a specified threshold, including only those with correlation coefficient values greater than 0.75, were overlaid on the corresponding B-mode image to aid in diagnosis. A scatter plot of the normalized area feature demonstrates the feasibility of developing a linear classifier to differentiate benign from malignant masses. The area under the receiver operator characteristic curve utilizing the normalized axial-shear Strain area feature was 0.996, demonstrating the potential of this feature to noninvasively differentiate between benign and malignant breast masses.
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Axial shear Strain Imaging for breast mass differentiation
2009 IEEE International Ultrasonics Symposium, 2009Co-Authors: Haiyan Xu, Tomy Varghese, Amy Sommer, Timothy J Hall, Gale A Sisney, Sara Baker, Elizabeth S BurnsideAbstract:Breast cancer remains the second-leading cause of cancer deaths in women, and over 200,000 new cases of invasive breast cancer are expected in the USA this year. Very promising data demonstrate that axial Strain Imaging has an important role in breast tissue classification However, another important parameter; the shear Strain has only recently been recognized as having great potential. We examine the feasibility of utilizing in-vivo axial shear Strain Imaging for differentiating benign from malignant breast masses. A VFX13-5 linear array transducer was utilized to acquire in-vivo radiofrequency echo data on 41 patients using a Siemens SONOLINE Antares real-time clinical scanner at the University of Wisconsin Breast Center. Free-hand palpation Imaging with deformation up to 10% was utilized to acquire radiofrequency data loops to generate Strain images. In this study, we report on 8 malignant tumors and 33 fibroadenomas to demonstrate the potential of shear Strain Imaging, compared to biopsy results that were considered the diagnostic standard. Axial Strain and axial component of shear Strain are estimated using an algorithm based on 2D cross-correlation. Areas of the axial-shear Strain, normalized to the lesion size, applied Strain and Strain contrast was utilized for differentiating benign from malignant masses. Our results on 40 patients indicate that the normalized axial-shear Strain area is significantly larger for malignant tumors when compared to benign fibroadenomas. Axial-shear Strain pixel values greater than a specified threshold, including only those with correlation coefficient values greater than 0.75, were overlaid on the corresponding B-mode image to aid in diagnosis. Scatter plot of the normalized area feature demonstrate the feasibility of developing a linear classifier to differentiate benign from malignant masses. The area under the Receiver Operating Characteristic curve using the normalized shear Strain area parameter was 0.996.
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Anthropomorphic phantoms for assessment of Strain Imaging methods involving saline-infused sonohysterography.
Ultrasound in medicine & biology, 2008Co-Authors: Maritza A. Hobson, Timothy J Hall, Jingfeng Jiang, Ernest L. Madsen, Gary R. Frank, Hairong Shi, Tomy VargheseAbstract:Abstract Two anthropomorphic uterine phantoms were developed that allow assessment and comparison of Strain Imaging systems adapted for use with saline-infused sonohysterography (SIS). Tissue-mimicking (TM) materials consist of dispersions of safflower oil in gelatin. TM fibroids are stiffer than the TM myometrium/cervix, and TM polyps are softer. The first uterine phantom has 3-mm-diameter TM fibroids distributed randomly in TM myometrium. The second uterine phantom has a 5-mm and 8-mm spherical TM fibroid, in addition to a 5-mm spherical and a 12.5-mm-long (medicine capsule–shaped) TM endometrial polyp protruding into the endometrial cavity; also, a 10-mm spherical TM fibroid projects from the serosal surface. Strain images using the first phantom show the stiffer 3-mm TM fibroids in the myometrium. Results from the second uterine phantom show that, as expected, parts of inclusions projecting into the uterine cavity will appear very stiff, whether they are stiff or soft. Results from both phantoms show that although there is a five-fold difference in the Young's moduli values, there is not a significant difference in the Strain in the transition from the TM myometrium to the TM fat. These phantoms allow for realistic comparison and evolution of SIS Strain Imaging techniques and can aid clinical personnel to develop skills for SIS Strain Imaging. (E-mail: mahobson@gmail.com )
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differentiating benign from malignant solid breast masses with us Strain Imaging
Radiology, 2007Co-Authors: Elizabeth S Burnside, Timothy J Hall, Gale A Sisney, Gina K Hesley, Amy M Sommer, W E Svensson, Jason P Fine, Jinfeng Jiang, Nicholas J HangiandreouAbstract:Purpose: To prospectively evaluate the sensitivity and specificity of ultrasonographic (US) Strain Imaging for distinguishing between benign and malignant solid breast masses, with biopsy results as the reference standard. Materials and Methods: The study was institutional review board approved and HIPAA compliant. Informed consent was obtained from all participating patients. US Strain Imaging of 403 breast masses was performed. The 50 malignant and 48 benign lesions (in patients aged 19–83 years; mean age, 49 years ± 17 [standard deviation]) with the highest quality were selected for the reader study. Three observers blinded to the pathologic outcomes first described the B-mode image findings by using US Breast Imaging Reporting and Data System descriptors and derived a probability of malignancy. They then updated the probability by assessing Strain images. Receiver operating characteristic (ROC) curves were constructed by using these probabilities. Areas under the ROC curve, sensitivities, and specific...
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A parallelizable real-time motion tracking algorithm with applications to ultrasonic Strain Imaging.
Physics in medicine and biology, 2007Co-Authors: Jingfeng Jiang, Timothy J HallAbstract:Ultrasound-based mechanical Strain Imaging systems utilize signals from conventional diagnostic ultrasound systems to image tissue elasticity contrast that provides new diagnostically valuable information. Previous works (Hall et al 2003 Ultrasound Med. Biol. 29 427, Zhu and Hall 2002 Ultrason. Imaging 24 161) demonstrated that uniaxial deformation with minimal elevation motion is preferred for breast Strain Imaging and real-time Strain image feedback to operators is important to accomplish this goal. The work reported here enhances the real-time speckle tracking algorithm with two significant modifications. One fundamental change is that the proposed algorithm is a column-based algorithm (a column is defined by a line of data parallel to the ultrasound beam direction, i.e. an A-line), as opposed to a row-based algorithm (a row is defined by a line of data perpendicular to the ultrasound beam direction). Then, displacement estimates from its adjacent columns provide good guidance for motion tracking in a significantly reduced search region to reduce computational cost. Consequently, the process of displacement estimation can be naturally split into at least two separated tasks, computed in parallel, propagating outward from the center of the region of interest (ROI). The proposed algorithm has been implemented and optimized in a Windows® system as a stand-alone ANSI C++ program. Results of preliminary tests, using numerical and tissue-mimicking phantoms, and in vivo tissue data, suggest that high contrast Strain images can be consistently obtained with frame rates (10 frames s−1) that exceed our previous methods.
Jingfeng Jiang - One of the best experts on this subject based on the ideXlab platform.
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TU‐E‐201C‐05: Electrode Displacement Strain Imaging for Monitoring In‐Vivo Ablative Therapies
Medical Physics, 2010Co-Authors: Nicholas Rubert, Jingfeng Jiang, James A. Zagzebski, Shyam Bharat, Ryan J. Dewall, Anita Andreano, Christopher L. Brace, Lisa A. Sampson, Fred T. Lee, Tomy VargheseAbstract:Purpose: Percutaneous RF ablation is evolving into an accepted minimally‐invasive treatment for hepatic tumors. Monitoring and delineating the treated region is essential for its success. Ultrasoundelastography can become a convenient and cost‐effective means to delineate thermal lesion boundaries. This study assesses electrode displacement based Strain Imaging for monitoring abdominal RF ablation procedures that are difficult to monitor with conventional elastography Method and Materials: Thirteen RFablated regions were created in‐vivo in pig liver.Radiofrequency echo signal data for Strain Imaging were acquired using a Siemens Antares clinical scanner immediately following RF ablation procedures. Small displacements were applied to the unconStrained end of the ablationelectrode in‐vivo, resulting in localized tissue deformation. Strain images were then compared to gross‐pathology images of the same lesion along the two‐dimensional Imaging plane. Gross‐pathology images were obtained by fixing the excised thermal lesion and slicing though the lesion, utilizing marks on the liver surface denoting the Imaging plane and visual inspection of the electrode track. Results: Cross‐sectional area measurements of the thermal lesion obtained from the Strain images were derived using both manual and automated segmentation. Areas were compared with cross‐sectional area measurements from gross pathology images. Area measurements from Strain images were highly correlated to areas measured on gross‐pathology, where the linear correlation coefficients were R = 0.894, P < 0.001 and R = 0.828, P < 0.001, for the manual and automated segmentation, respectively. Conclusions:Electrode displacement based Strain Imaging provides high contrast between ablated and normal liver tissue, allowing for clear delineation of the thermal ablation zone. This complements clinical ultrasound Imaging, the preferred modality for real‐time guidance for the placement of the RF needle into the tumor, allowing multiple Imaging tasks to be performed with a single ultrasound machine. Supported by NIH‐NCI grants R01CA112192‐03 and R01CA112192‐S103.
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Electrode displacement Strain Imaging of thermally‐ablated liver tissue in an in vivo animal model
Medical physics, 2010Co-Authors: Nicholas Rubert, Jingfeng Jiang, Shyam Bharat, Ryan J. Dewall, Anita Andreano, Christopher L. Brace, Lisa A. Sampson, Tomy VargheseAbstract:Purpose: Percutaneous thermal ablation is increasingly being used to destroy hepatic tumorsin situ. The success of ablative techniques is highly dependent on adequate ablation zone monitoring, and ultrasound-based Strain Imaging could become a convenient and cost-effective means to delineate ablation zone boundaries. This study investigates in vivo electrode displacement-based Strain Imaging for monitoring hepatic ablation procedures that are difficult to perform with conventional elastography. Methods: In our method, minute displacements (less than a millimeter) are applied to the unconStrained end of the ablation electrode, resulting in localized tissue deformation within the ablation zone that provides the mechanical stimuli required for Strain Imaging. This article presents electrode displacement Strain images of radiofrequency ablation zones created in porcine liver in vivo (n=13). Results: Cross-sectional area measurements from Strain images of these ablation zones were obtained using manual and automated segmentation. Area measurements from Strain images were highly correlated with areas measured on histopathology images, quantitated using linear regression (R=0.894, P
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In vivo ultrasound electrode displacement Strain Imaging
2009 IEEE International Ultrasonics Symposium, 2009Co-Authors: Nicholas Rubert, Jingfeng Jiang, James A. Zagzebski, Shyam Bharat, Ryan J. Dewall, Anita Andreano, Christopher L. Brace, Lisa A. Sampson, Fred T. Lee, Tomy VargheseAbstract:The incidence of primary and secondary liver tumors has increased significantly over the last two decades. Due to poor liver function and/or distribution of lesions, surgery is often not an option for affected patients. An alternative to surgical resection, percutaneous radiofrequency ablation is often used to thermally destroy the tumor in situ. Radiofrequency ablation is evolving into one of the more popular minimally-invasive treatments for hepatic tumors. Monitoring the treated region is an important factor in the success of radiofrequency ablation, and ultrasound elastography could become a convenient, cost-effective means to delineate the thermal lesion boundaries for clinical personnel during the procedure. This study assesses “electrode displacement” Strain Imaging for monitoring abdominal radiofrequency ablation procedures. We present results utilizing a novel approach of displacing the ablation electrode itself to introduce the mechanical stimuli required for Strain Imaging. Utilizing a Siemens Antares clinical ultrasound scanner equipped with a research interface, ultrasound radiofrequency data were acquired immediately following radiofrequency ablation of porcine liver. The porcine liver was excised following the procedure, and the dimensions of the thermal lesion in the Imaging plane measured by slicing though the lesion. Strain images of the lesions were produced offline using axial guidance based block-matching and multi-level motion tracking algorithms. The area of the lesion on the Strain image was compared to the area of the lesion in pathology images obtained from eight separate lesions. The estimated linear correlation coefficient between the pathology image and the Strain image was r = 0.961 (p ≪ .001) for manual segmentation using 4 observers. The area of the lesion in the Strain image slightly underestimates the area of the lesion in the pathology image for all slices, agreeing with earlier ex-vivo experiments.
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Anthropomorphic phantoms for assessment of Strain Imaging methods involving saline-infused sonohysterography.
Ultrasound in medicine & biology, 2008Co-Authors: Maritza A. Hobson, Timothy J Hall, Jingfeng Jiang, Ernest L. Madsen, Gary R. Frank, Hairong Shi, Tomy VargheseAbstract:Abstract Two anthropomorphic uterine phantoms were developed that allow assessment and comparison of Strain Imaging systems adapted for use with saline-infused sonohysterography (SIS). Tissue-mimicking (TM) materials consist of dispersions of safflower oil in gelatin. TM fibroids are stiffer than the TM myometrium/cervix, and TM polyps are softer. The first uterine phantom has 3-mm-diameter TM fibroids distributed randomly in TM myometrium. The second uterine phantom has a 5-mm and 8-mm spherical TM fibroid, in addition to a 5-mm spherical and a 12.5-mm-long (medicine capsule–shaped) TM endometrial polyp protruding into the endometrial cavity; also, a 10-mm spherical TM fibroid projects from the serosal surface. Strain images using the first phantom show the stiffer 3-mm TM fibroids in the myometrium. Results from the second uterine phantom show that, as expected, parts of inclusions projecting into the uterine cavity will appear very stiff, whether they are stiff or soft. Results from both phantoms show that although there is a five-fold difference in the Young's moduli values, there is not a significant difference in the Strain in the transition from the TM myometrium to the TM fat. These phantoms allow for realistic comparison and evolution of SIS Strain Imaging techniques and can aid clinical personnel to develop skills for SIS Strain Imaging. (E-mail: mahobson@gmail.com )
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A parallelizable real-time motion tracking algorithm with applications to ultrasonic Strain Imaging.
Physics in medicine and biology, 2007Co-Authors: Jingfeng Jiang, Timothy J HallAbstract:Ultrasound-based mechanical Strain Imaging systems utilize signals from conventional diagnostic ultrasound systems to image tissue elasticity contrast that provides new diagnostically valuable information. Previous works (Hall et al 2003 Ultrasound Med. Biol. 29 427, Zhu and Hall 2002 Ultrason. Imaging 24 161) demonstrated that uniaxial deformation with minimal elevation motion is preferred for breast Strain Imaging and real-time Strain image feedback to operators is important to accomplish this goal. The work reported here enhances the real-time speckle tracking algorithm with two significant modifications. One fundamental change is that the proposed algorithm is a column-based algorithm (a column is defined by a line of data parallel to the ultrasound beam direction, i.e. an A-line), as opposed to a row-based algorithm (a row is defined by a line of data perpendicular to the ultrasound beam direction). Then, displacement estimates from its adjacent columns provide good guidance for motion tracking in a significantly reduced search region to reduce computational cost. Consequently, the process of displacement estimation can be naturally split into at least two separated tasks, computed in parallel, propagating outward from the center of the region of interest (ROI). The proposed algorithm has been implemented and optimized in a Windows® system as a stand-alone ANSI C++ program. Results of preliminary tests, using numerical and tissue-mimicking phantoms, and in vivo tissue data, suggest that high contrast Strain images can be consistently obtained with frame rates (10 frames s−1) that exceed our previous methods.
Richard W. Prager - One of the best experts on this subject based on the ideXlab platform.
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Initial clinical experience of an ultrasonic Strain Imaging system with novel noise-masking capability.
The British journal of radiology, 2010Co-Authors: Lujie Chen, Richard W. Prager, Andrew H. Gee, S J Freeman, Rj Housden, R Sinnatamby, Graham M. TreeceAbstract:Quasistatic Strain Imaging is a form of elastography that can produce qualitative images of tissue stiffness with only software modifications to conventional ultrasound hardware. Unlike current commercial offerings, the novel Strain-Imaging system that is the subject of this paper displays regions of signal decorrelation using an overlaid colour mask and can also produce three-dimensional (3D) Strain images. In illustrative studies of the breast, testis and thyroid, the colour mask is seen to reduce the potential to misinterpret noise as meaningful stiffness information, and also helps to differentiate cystic and solid lesions. High-quality Imaging of the testis in vivo demonstrates that 3D Strain Imaging is feasible.
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Uniform precision ultrasound Strain Imaging
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2009Co-Authors: Graham M. Treece, Joel E. Lindop, Richard W. PragerAbstract:Ultrasound Strain Imaging is becoming increasingly popular as a way to measure stiffness variation in soft tissue. Almost all techniques involve the estimation of a field of relative displacements between measurements of tissue undergoing different deformations. These estimates are often high resolution, but some form of smoothing is required to increase the precision, either by direct filtering or as part of the gradient estimation process. Such methods generate uniform resolution images, but Strain quality typically varies considerably within each image, hence a trade-off is necessary between increasing precision in the low-quality regions and reducing resolution in the high-quality regions. We introduce a smoothing technique, developed from the nonparametric regression literature, which can avoid this trade-off by generating uniform precision images. In such an image, high resolution is retained in areas of high Strain quality but sacrificed for the sake of increased precision in low-quality areas. We contrast the algorithm with other methods on simulated, phantom, and clinical data, for both 2-D and 3-D Strain Imaging. We also show how the technique can be efficiently implemented at real-time rates with realistic parameters on modest hardware. Uniform precision nonparametric regression promises to be a useful tool in ultrasound Strain Imaging.
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Stable, Intelligible Ultrasonic Strain Imaging
Ultrasound (Leeds England), 2008Co-Authors: Andrew H. Gee, Graham M. Treece, Richard W. Prager, Je Lindop, Susan FreemanAbstract:Background: Freehand quasistatic Strain Imaging can reveal qualitative information about tissue stiffness with good spatial accuracy. Clinical trials, however, repeatedly cite instability and variable signal-to-noise ratio as significant drawbacks.Methods: This study investigates three post-processing strategies for quasistatic Strain Imaging. Normalization divides the Strain by an estimate of the stress field, the intention being to reduce sensitivity to variable applied stress. Persistence aims to improve the signal-to-noise ratio by time-averaging multiple frames. The persistence scheme presented in this article operates at the pixel level, weighting each frame's contribution by an estimate of the Strain precision. Precision-based display presents the clinician with an image in which regions of indeterminate Strain are obscured behind a colour wash. This is achieved using estimates of Strain precision that are faithfully propagated through the various stages of signal processing.Results and discussion:...
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An intelligent interface for freehand Strain Imaging.
Ultrasound in medicine & biology, 2008Co-Authors: Je Lindop, Graham M. Treece, Andrew H. Gee, Richard W. PragerAbstract:Abstract We present a new, intelligent interface for freehand Strain Imaging, which has been designed to support clinical trials investigating the potential of ultrasonic Strain Imaging for diagnostic purposes across a broad range of target pathologies. The aim with this interface is to make scanning easier and to help clinicians learn the necessary scanning technique quickly, by providing real time feedback indicating the quality of the Strain data as they are produced. The methods require a pixel-level indicator of estimation precision, which can be calculated in-line with Strain estimation. This is exploited in novel approaches to normalisation, persistence and display. The effect of each component is indicated in the results with examples from in vitro and in vivo scanning. As well as providing real-time feedback, the images are easier to interpret because data at unacceptably low signal-to-noise ratios do not reach the display. Additionally, the level of noise in the displayed images is actually reduced compared with other methods that use the same Strain estimates with the same level of persistence. The interface also considerably reduces the difficulty in producing volumes of Strain data from freehand three-dimensional scans. (E-mail: jel35@eng.cam.ac.uk )
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Dynamic resolution selection in ultrasonic Strain Imaging.
Ultrasound in medicine & biology, 2008Co-Authors: Je Lindop, Graham M. Treece, Andrew H. Gee, Richard W. PragerAbstract:Ultrasonic Strain Imaging promises to be a valuable tool in medical diagnostics. Reliability and ease-of-use have become important considerations. These depend on selection of appropriate Imaging parameters. Two tasks are undertaken here. The tradeoff between resolution and estimation precision is examined closely to establish models for the relationships with Imaging parameters and data properties. These models are then applied in a system that automatically sets the Imaging parameters responsive to the data quality and the required estimation precision, so as to produce more meaningful images under varying scan conditions. The new system is applied to simulation, in vitro and in vivo data for validation. It reduces the complexity of the sonographer's role in Strain Imaging, and produces images of reliable quality even when the level of signal decorrelation varies throughout the ultrasound data.
Matthew O'donnell - One of the best experts on this subject based on the ideXlab platform.
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Thermal Strain Imaging: a review
Interface focus, 2011Co-Authors: Chi Hyung Seo, Sheng-wen Huang, Kang Kim, Y. Shi, Matthew O'donnellAbstract:Thermal Strain Imaging (TSI) or temporal Strain Imaging is an ultrasound application that exploits the temperature dependence of sound speed to create thermal (temporal) Strain images. This article provides an overview of the field of TSI for biomedical applications that have appeared in the literature over the past several years. Basic theory in thermal Strain is introduced. Two major energy sources appropriate for clinical applications are discussed. Promising biomedical applications are presented throughout the paper, including non-invasive thermometry and tissue characterization. We present some of the limitations and complications of the method. The paper concludes with a discussion of competing technologies.
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A multi-resolution displacement estimator for ultrasonic myocardial Strain Imaging
2009 IEEE International Ultrasonics Symposium, 2009Co-Authors: Lingyun Huang, Sheng-wen Huang, Chi Hyung Seo, Congxian Jia, Matthew O'donnellAbstract:Low signal-to-noise ratio regions and large deformations in myocardial Strain Imaging cause peak hopping artifacts, especially near peak systole. To solve this problem, we propose a multi-resolution Viterbi search algorithm to maximally utilize tissue continuity and finite Strain conStraints to improve displacement estimation. Data from an isolated rabbit heart experiment were used to validate the proposed algorithm. An 86.1% reduction in peak hopping artifacts strongly suggests that the proposed algorithm is effective for myocardial Strain Imaging.
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Feasibility of applying ultrasound Strain Imaging to detect renal transplant chronic allograft nephropathy
Kidney international, 2004Co-Authors: William F. Weitzel, Jonathan M. Rubin, Kang Kim, Roger C. Wiggins, Hua Xie, Xunchang Chen, Stanislav Emelianov, Matthew O'donnellAbstract:Feasibility of applying ultrasound Strain Imaging to detect renal transplant chronic allograft nephropathy. Chronic renal transplant fibrosis, often termed Chronic Allograft Nephropathy, may progress undetected. Since renal fibrosis may be accompanied by a change in measurable elastic tissue properties, ultrasound Strain measurements may be useful in its detection. Ultrasound Strain Imaging was performed for two subjects with renal transplants; one with normal renal function and one with mild renal insufficiency and biopsy demonstrated fibrosis. Subjects underwent ultrasound examination with application of a controlled deformation using phase-sensitive, two-dimensional speckle tracking to evaluate internal tissue motion to measure tissue displacement and Strain. Measurements over multiple beams for an equivalent deformational stress showed there was a threefold differences in renal cortical Strain between the two subjects. These data suggest that ultrasound elasticity Imaging may prove useful in measuring mechanical changes related to fibrosis within the transplant kidney.
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An integrated compliant balloon ultrasound catheter for intravascular Strain Imaging
IEEE transactions on ultrasonics ferroelectrics and frequency control, 2002Co-Authors: C.d. Choi, Stanislav Emelianov, A.r. Skovoroda, Matthew O'donnellAbstract:An integrated compliant balloon ultrasound catheter was developed to allow greater deformations in Strain Imaging with intravascular ultrasound. A 64-element circumferential array was placed inside a compliant silicone balloon catheter to capture real-time, phase-sensitive radio frequency (RF) data during deformation experiments. Strains over 40% could be applied to normal arterial wall tissue with intracatheter pressures as low as 200 kPa (2 atm). Strain images of a hard-soft rubber phantom, thrombus, and fibrotic plaque were produced using the integrated balloon ultrasound catheter. Results show that this catheter can apply large deformations at low pressures and image various vascular pathologies ex vivo. Potentially, it can serve as a multifunctional, intravascular therapeutic device to guide angioplasty and stent deployment.
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Strain Imaging of vascular pathologies using a compliant balloon catheter
2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121), 1Co-Authors: C.d. Choi, Stanislav Emelianov, A.r. Skovoroda, Matthew O'donnellAbstract:An integrated compliant silicone balloon catheter was developed to allow greater deformations in Strain Imaging with intravascular ultrasound. An Endosonics 64-element array was placed inside a compliant balloon catheter to capture real-time phase-sensitive radio frequency (rf) data during deformation experiments. A hard-soft rubber phantom, thrombus, and fibrotic plaque were imaged using the integrated compliant balloon/ultrasound catheter to produce Strain images. The results show that an integrated compliant balloon/ultrasound catheter can apply large deformations at low pressures and image various vascular pathologies ex vivo. This catheter could serve as a multi-functional intravascular therapeutic device to guide angioplasty and stent deployment.