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Ultrasonic Imaging

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https://www.readbyqxmd.com/read/28395599/high-frequency-ultrasonic-imaging-with-lead-free-na-k-nb-ta-o3-single-crystal
#1
Zeyu Chen, Limei Zheng, Wenwu Cao, Xiaoyang Chen, Ruimin Chen, Runze Li, Kirk Shung, Qifa Zhou
Lead-free (Na,K)(Nb,Ta)O3 (KNNT) piezoelectric single crystal has been successfully grown using the top-seeded solution growth technique. The electromechanical coupling factors are very high ( k33 = 0.827, kt = 0.646), and the dielectric loss tangent is as low as 0.004. Acoustic impedance was calculated to be 26.5 MRayl. From the single crystal, a single element transducer was fabricated. The transducer achieved a 57.6% -6 dB bandwidth and 32.3 µm axial resolution at the center frequency of 45.4 MHz, which can identify the cornea of porcine eyeball with high resolution...
April 1, 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28345418/a-coaxial-dual-element-focused-ultrasound-probe-for-guidance-of-epidural-catheterization
#2
Guo-Chung Dong, Li-Chen Chiu, Chien-Kun Ting, Jia-Ruei Hsu, Chih-Chung Huang, Yin Chang, Gin-Shin Chen
Ultrasound guidance for epidural block has improved clinical blind-trial problems but the design of present ultrasonic probes poses operating difficulty of ultrasound-guided catheterization, increasing the failure rate. The purpose of this study was to develop a novel ultrasonic probe to avoid needle contact with vertebral bone during epidural catheterization. The probe has a central circular passage for needle insertion. Two focused annular transducers are deployed around the passage for on-axis guidance. A 17-gauge insulated Tuohy needle containing the self-developed fiber-optic-modified stylet was inserted into the back of the anesthetized pig, in the lumbar region under the guidance of our ultrasonic probe...
March 1, 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28425388/lower-bound-on-estimation-variance-of-the-ultrasonic-attenuation-coefficient-using-the-spectral-difference-reference-phantom-method
#3
Kayvan Samimi, Tomy Varghese
Ultrasonic attenuation is one of the primary parameters of interest in Quantitative Ultrasound (QUS). Non-invasive monitoring of tissue attenuation can provide valuable diagnostic and prognostic information to the physician. The Reference Phantom Method (RPM) was introduced as a way of mitigating some of the system-related effects and biases to facilitate clinical QUS applications. In this paper, under the assumption of diffuse scattering, a probabilistic model of the backscattered signal spectrum is used to derive a theoretical lower bound on the estimation variance of the attenuation coefficient using the Spectral-Difference RPM...
May 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28091280/rotation-elastogram-estimation-using-synthetic-transmit-aperture-technique-a-feasibility-study
#4
Lokesh B, Bhaskara Rao Chintada, Arun Kumar Thittai
It is well-documented in literature that benign breast lesions, such as fibroadenomas, are loosely bonded to their surrounding tissue and tend to slip under a small quasi-static compression, whereas malignant lesions being firmly bonded to their surrounding tissue do not slip. Recent developments in quasi-static ultrasound elastography have shown that an image of the axial-shear strain distribution can provide information about the bonding condition at the lesion-surrounding tissue boundary. Further studies analyzing the axial-shear strain elastograms revealed that nonzero axial-shear strain values appear inside the lesion, referred to as fill-in, only when a lesion is loosely bonded and asymmetrically oriented to the axis of compression...
May 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/27903789/a-color-doppler-shear-wave-imaging-phase-reconstruction-method-using-four-color-flow-images
#5
Naoki Sunaguchi, Yoshiki Yamakoshi, Takahito Nakajima
This study investigates shear wave phase map reconstruction using a limited number of color flow images (CFIs) acquired with a color Doppler ultrasound imaging instrument. We propose an efficient reconstruction method to considerably reduce the number of CFIs required for reconstruction and compare this method with Fourier analysis-based color Doppler shear wave imaging. The proposed method uses a two-step phase reconstruction process, including an initial phase map derived from four CFIs using an advanced iterative algorithm of optical interferometry...
May 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/27488348/virtual-breast-quasi-static-elastography-vbqe
#6
David Rosen, Yu Wang, Jingfeng Jiang
Viscoelasticity Imaging (VEI) has been proposed to measure relaxation time constants for characterization of in vivo breast lesions. In this technique, an external compression force on the tissue being imaged is maintained for a fixed period of time to induce strain creep. A sequence of ultrasound echo signals is then utilized to generate time-resolved strain measurements. Relaxation time constants can be obtained by fitting local time-resolved strain measurements to a viscoelastic tissue model (e.g., a modified Kevin-Voigt model)...
March 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28068874/short-lag-spatial-coherence-ultrasound-imaging-with-adaptive-synthetic-transmit-aperture-focusing
#7
Jinxin Zhao, Yuanyuan Wang, Jinhua Yu, Wei Guo, Shun Zhang, Saeid Aliabadi
The short-lag spatial coherence (SLSC) imaging has been demonstrated to be advantageous over the traditional B-mode ultrasound imaging. With focused scanning beams, the SLSC imaging has an excellent performance in clutter reduction and lesion detection, especially in the low signal-to-noise ratio (SNR) scenarios. The synthetic aperture (SA) imaging is an appropriate mode for the SLSC imaging as the dynamic transmit focusing could keep a good focusing quality at any depth. However, the SLSC image may still suffer a bad resolution performance when a low lag value is used in the coherence summation to ensure the contrast enhancement...
January 1, 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26586725/segmentation-of-breast-lesions-in-ultrasound-images-through-multiresolution-analysis-using-undecimated-discrete-wavelet-transform
#8
K M Prabusankarlal, P Thirumoorthy, R Manavalan
Earliest detection and diagnosis of breast cancer reduces mortality rate of patients by increasing the treatment options. A novel method for the segmentation of breast ultrasound images is proposed in this work. The proposed method utilizes undecimated discrete wavelet transform to perform multiresolution analysis of the input ultrasound image. As the resolution level increases, although the effect of noise reduces, the details of the image also dilute. The appropriate resolution level, which contains essential details of the tumor, is automatically selected through mean structural similarity...
November 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26578642/segmental-analysis-of-cardiac-short-axis-views-using-lagrangian-radial-and-circumferential-strain
#9
Chi Ma, Xiao Wang, Tomy Varghese
Accurate description of myocardial deformation in the left ventricle is a three-dimensional problem, requiring three normal strain components along its natural axis, that is, longitudinal, radial, and circumferential strains. Although longitudinal strains are best estimated from long-axis views, radial and circumferential strains are best depicted in short-axis views. An algorithm that utilizes a polar grid for short-axis views previously developed in our laboratory for a Lagrangian description of tissue deformation is utilized for radial and circumferential displacement and strain estimation...
November 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/27694129/effect-of-interstitial-fluid-pressure-on-ultrasound-axial-strain-and-axial-shear-strain-elastography
#10
Anuj Chaudhry, Namhee Kim, Ginu Unnikrishnan, Sanjay Nair, J N Reddy, Raffaella Righetti
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...
September 29, 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/27659687/a-pilot-clinical-study-in-characterization-of-malignant-renal-cell-carcinoma-subtype-with-contrast-enhanced-ultrasound
#11
Sandeep K Kasoji, Emily H Chang, Lee B Mullin, Wui K Chong, W Kimryn Rathmell, Paul A Dayton
Malignant renal cell carcinoma (RCC) is a diverse set of diseases, which are independently difficult to characterize using conventional MRI and CT protocols due to low temporal resolution to study perfusion characteristics. Because different disease subtypes have different prognoses and involve varying treatment regimens, the ability to determine RCC subtype non-invasively is a clinical need. Contrast-enhanced ultrasound (CEUS) has been assessed as a tool to characterize kidney lesions based on qualitative and quantitative assessment of perfusion patterns, and we hypothesize that this technique might help differentiate disease subtypes...
September 22, 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26614530/experimental-validation-of-arfi-surveillance-of-subcutaneous-hemorrhage-assh-using-calibrated-infusions-in-a-tissue-mimicking-model-and-dogs
#12
Rebecca E Geist, Chase H DuBois, Timothy C Nichols, Melissa C Caughey, Elizabeth P Merricks, Robin Raymer, Caterina M Gallippi
Acoustic radiation force impulse (ARFI) Surveillance of Subcutaneous Hemorrhage (ASSH) has been previously demonstrated to differentiate bleeding phenotype and responses to therapy in dogs and humans, but to date, the method has lacked experimental validation. This work explores experimental validation of ASSH in a poroelastic tissue-mimic and in vivo in dogs. The experimental design exploits calibrated flow rates and infusion durations of evaporated milk in tofu or heparinized autologous blood in dogs. The validation approach enables controlled comparisons of ASSH-derived bleeding rate (BR) and time to hemostasis (TTH) metrics...
September 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26400676/a-review-of-intravascular-ultrasound-based-multimodal-intravascular-imaging-the-synergistic-approach-to-characterizing-vulnerable-plaques
#13
Teng Ma, Bill Zhou, Tzung K Hsiai, K Kirk Shung
Catheter-based intravascular imaging modalities are being developed to visualize pathologies in coronary arteries, such as high-risk vulnerable atherosclerotic plaques known as thin-cap fibroatheroma, to guide therapeutic strategy at preventing heart attacks. Mounting evidences have shown three distinctive histopathological features-the presence of a thin fibrous cap, a lipid-rich necrotic core, and numerous infiltrating macrophages-are key markers of increased vulnerability in atherosclerotic plaques. To visualize these changes, the majority of catheter-based imaging modalities used intravascular ultrasound (IVUS) as the technical foundation and integrated emerging intravascular imaging techniques to enhance the characterization of vulnerable plaques...
September 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26376923/indentation-measurements-to-validate-dynamic-elasticity-imaging-methods
#14
Khaldoon N Altahhan, Yue Wang, Nahil Sobh, Michael F Insana
We describe macro-indentation techniques for estimating the elastic modulus of soft hydrogels. Our study describes (a) conditions under which quasi-static indentation can validate dynamic shear-wave imaging estimates and (b) how each of these techniques uniquely biases modulus estimates as they couple to the sample geometry. Harmonic shear waves between 25 and 400 Hz were imaged using ultrasonic Doppler and optical coherence tomography methods to estimate shear dispersion. From the shear-wave speed of sound, average elastic moduli of homogeneous samples were estimated...
September 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26346886/can-elastography-predict-growth-of-incidental-thyroid-nodules-a-pilot-two-year-follow-up-study
#15
Anne Krejbjerg, Inge Bülow Pedersen, Peter Laurberg
The objective of this study was to examine the ultrasonography (US) and ultrasound elastography (USE) features of thyroid incidentalomas in a population exposed to iodine deficiency and to investigate whether baseline elasticity scores (ES) predicted changes in thyroid nodule US characteristics. We conducted a two-year follow-up pilot study of thyroid incidentalomas by US and USE. One sonographer performed the US and USE examination on the same apparatus at baseline and at follow-up. We evaluated 83 incidental thyroid nodules detected in a population study...
September 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26416839/backscatter-difference-measurements-of-cancellous-bone-using-an-ultrasonic-imaging-system
#16
Brent K Hoffmeister, Morgan R Smathers, Catherine J Miller, Joseph A McPherson, Cameron R Thurston, P Luke Spinolo, Sang-Rok Lee
Backscatter-difference measurements may be used to detect changes in bone caused by osteoporosis. The backscatter-difference technique measures the power difference between two portions of an ultrasonic backscatter signal. The goal of this study is to evaluate the feasibility of using an ultrasonic imaging system to perform backscatter-difference measurements of bone. Ultrasonic images and backscatter signals were acquired from 24 specimens of human cancellous bone. The signals were analyzed in the frequency domain to determine the normalized mean backscatter-difference (nMBD) and in the time domain to determine the normalized backscatter amplitude ratio (nBAR)...
July 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26333280/combining-the-apes-and-minimum-variance-beamformers-for-adaptive-ultrasound-imaging
#17
Babak Mohammadzadeh Asl
In recent years, adaptive minimum-variance (MV) beamforming has been successfully applied to medical ultrasound imaging, resulting in simultaneous improvement in imaging resolution and contrast. MV has high resolution and hence can provide accurate estimates of the target locations. However, the MV amplitude estimates are significantly biased downward, especially when occurring the errors in model parameters. The amplitude and phase estimation (APES) beamformer gives much more accurate amplitude estimates at the target locations, but at the cost of lower resolution...
July 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26316172/nonlocal-total-variation-based-speckle-filtering-for-ultrasound-images
#18
Tiexiang Wen, Jia Gu, Ling Li, Wenjian Qin, Lei Wang, Yaoqin Xie
Ultrasound is one of the most important medical imaging modalities for its real-time and portable imaging advantages. However, the contrast resolution and important details are degraded by the speckle in ultrasound images. Many speckle filtering methods have been developed, but they are suffered from several limitations, difficult to reach a balance between speckle reduction and edge preservation. In this paper, an adaptation of the nonlocal total variation (NLTV) filter is proposed for speckle reduction in ultrasound images...
July 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/26294659/handheld-thermoacoustic-scanning-system-based-on-a-linear-array-transducer
#19
Zhong Ji, Wenzheng Ding, Fanghao Ye, Cunguang Lou
To receive the information necessary for imaging, traditional microwave-induced thermoacoustic imaging systems (MITISs) use a type of circular-scanning mode using single or arc detectors. However, the use of MITISs for body scanning is complicated by restrictions in space and imaging time. A linear-array detector, the most widely used transducer in medical ultrasound imaging systems for body scanning, is a possible alternative to MITISs for scanning biological tissues, such as from the breast or limbs. In this paper, a handheld MITIS, based on a linear-array detector and a multiple data acquisition system, is described, and the capacity of the system is explored experimentally...
July 2016: Ultrasonic Imaging
https://www.readbyqxmd.com/read/27333883/impact-of-modified-anisotropic-diffusion-based-enhancement-method-in-computer-aided-classification-of-focal-liver-lesions
#20
Deepti Mittal
This work is presented with the objective to assess quantitatively the impact of modified anisotropic diffusion-based enhancement method of Mittal et al. in computer-aided classification of focal liver lesions. This assessment was made before and after enhancement of clinically acquired ultrasound images with the comparison of (a) discrimination capability of radiologically important texture contrast feature using box plot and p-value statistics and (b) test results of designed computer-aided classification schemes to detect/classify focal liver tissues using receiver operating characteristic curves...
June 22, 2016: Ultrasonic Imaging
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