Axial strain calculation using a low-pass digital differentiator in ultrasound elastography

2004 ◽  
Vol 51 (9) ◽  
pp. 1119-1127 ◽  
Author(s):  
Jianwen Luo ◽  
Jing Bai ◽  
Ping He ◽  
Kui Ying
Keyword(s):  
Axial Strain ◽  
Ultrasound Elastography ◽  
Digital Differentiator ◽  
Strain Calculation ◽  
Low Pass

Necking phenomenon based on the Aramis system

2018 ◽  
Vol 233 (11) ◽  
pp. 3904-3916 ◽  
Author(s):  
Shier Dong ◽  
Anjiang Xian ◽  
Zhanghua Lian ◽  
Hazem Samih Mohamed ◽  
Hongyu Ren
Keyword(s):  
Distribution Function ◽  
Strain Distribution ◽  
Axial Strain ◽  
Three Dimensional ◽  
Correlation Method ◽  
Tensile Tests ◽  
Image Correlation ◽  
Calculation Error ◽  
Strain Calculation ◽  
Deformation Properties

In this study, the necking three-dimensional strain on minimum cross-section at room temperature was performed experimentally and analytically. A modified strain assumption was applied to overcome significant errors in calculating necking strain by Bridgman assumption. Then, one relatively simple strain distribution function was deduced based on equilibrium equation of necking element. To obtain the parameters in this function, the monotonic tensile tests in two kinds of carbon structure steels Q235 and Q345 were carried out. Meanwhile, the Aramis system based on digital image correlation method was adopted to measure the surface axial strain and deformation parameters during the loading process. The experimental and numerical results were compared with the traditional Bridgman strain assumption. The maximum axial strain calculation error the strain distribution function and experiment value was less than 8%, which was obviously less than that calculated by Bridgman assumption. Additionally, the variation law of the three-dimensional strain calculated by this function was consistent with that obtained by the macroscopic analysis of fracture surface. The application of traditional Bridgman formula can be expanded by this study. Meanwhile, it can provide a new idea to study the stress distribution characteristics and better understanding of ductile materials’ deformation properties.

Improvement of Lesion Detection by Complete Angular Compound Ultrasonic Elastography

2016 ◽  
Vol 39 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Chenhui Liu ◽  
Yufeng Zhou
Keyword(s):  
Soft Tissues ◽  
Imaging Modality ◽  
Axial Strain ◽  
Lesion Detection ◽  
Ultrasound Elastography ◽  
Internal Boundary ◽  
Ultrasound Images ◽  
Stress Concentrations ◽  
Lateral Direction ◽  
Noise Ratio

Quasi-static ultrasound elastography is an emerging diagnostic imaging modality for determining the stiffness of pathologically changed soft tissues, which do not show significant differences in acoustic impedance for B-mode imaging. Although some methods were applied to improve the signal-to-noise ratio (SNRe) and contrast-to-noise ratio (CNRe) of the constructed elastogram, nonuniform strain distribution at the internal boundary of a hard inclusion, even with the uniform displacement on the surface, is an inherent mechanical effect and results in distortion at the detected lesion boundary. To overcome such stress concentrations, a new elastographic modality was proposed, where the elastograms from different angles throughout 360° were compounded. The strain field and subsequent ultrasound images were calculated using the finite element method (FEM) and Field II, respectively, from which the elastograms were constructed. The performance of complete angular compound elastography with varied interval angles, lesion sizes, and ratios of Young’s moduli of the lesion to the background was simulated and compared with that of conventional axial strain elastography. It is found that viewing the lesion from only about 10 angles (interval of 36°) would significantly improve the image quality of elastogram (increasing SNRe by at least 13% and CNRe by at least 5.8 dB), reduce the lesion distortion in the lateral direction, and enhance the sensitivity, resolution, and accuracy of lesion detection. A preliminary phantom study showed similar improvements. Altogether, complete angular compound elastography improves the elastogram quality and reduces the mechanical effects in lesion detection.

scholarly journals Spatial Angular Compounding for Elastography without the Incompressibility Assumption

2005 ◽  
Vol 27 (4) ◽  
pp. 256-270 ◽  
Author(s):  
Min Rao ◽  
Tomy Varghese
Keyword(s):  
Least Squares ◽  
Signal To Noise Ratio ◽  
Angular Displacement ◽  
Axial Strain ◽  
Beam Steering ◽  
Weighted Average ◽  
Local Strain ◽  
Ultrasound Elastography ◽  
Ultrasound Simulation ◽  
Noise Ratio

Spatial-angular compounding is a new technique that enables the reduction of noise artifacts in ultrasound elastography. Previous results using spatial angular compounding, however, were based on the use of the tissue incompressibility assumption. Compounded elastograms were obtained from a spatially-weighted average of local strain estimated from radiofrequency echo signals acquired at different insonification angles. In this paper, we present a new method for reducing the noise artifacts in the axial strain elastogram utilizing a least-squares approach on the angular displacement estimates that does not use the incompressibility assumption. This method produces axial strain elastograms with higher image quality, compared to noncompounded axial strain elastograms, and is referred to as the least-squares angular-compounding approach for elastography. To distinguish between these two angular compounding methods, the spatial-angular compounding with angular weighting based on the tissue incompressibility assumption is referred to as weighted compounding. In this paper, we compare the performance of the two angular-compounding techniques for elastography using beam steering on a linear-array transducer. Quantitative experimental results demonstrate that least-squares compounding provides comparable but smaller improvements in both the elastographic signal-to-noise ratio and the contrast-to-noise ratio, as compared to the weighted-compounding method. Ultrasound simulation results suggest that the least-squares compounding method performs better and provide accurate and robust results when compared to the weighted compounding method, in the case where the incompressibility assumption does not hold.

Effect of Interstitial Fluid Pressure on Ultrasound Axial Strain and Axial Shear Strain Elastography

2016 ◽  
Vol 39 (2) ◽  
pp. 137-146 ◽  
Author(s):  
Anuj Chaudhry ◽  
Namhee Kim ◽  
Ginu Unnikrishnan ◽  
Sanjay Nair ◽  
J. N. Reddy ◽  
...  
Keyword(s):  
Shear Strain ◽  
Interstitial Fluid ◽  
Malignant Tumors ◽  
Axial Strain ◽  
Fluid Pressure ◽  
Ultrasound Elastography ◽  
Interstitial Fluid Pressure ◽  
Major Barrier ◽  
Strain Elastography ◽  
Axial Shear

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.

Application of cross correlation to HREM images of surfaces

1987 ◽  
Vol 45 ◽  
pp. 754-755
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett
Keyword(s):  
Cross Correlation ◽  
A Priori ◽  
Matrix Material ◽  
Correlation Method ◽  
Accurate Knowledge ◽  
Complex Image ◽  
Fourier Filtering ◽  
The Matrix ◽  
Low Pass ◽  
Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

The S-SH Confusion Test and the Effects of Frequency Lowering

2019 ◽  
Vol 62 (5) ◽  
pp. 1486-1505
Author(s):  
Joshua M. Alexander
Keyword(s):  
Cognitive Processing ◽  
Hearing Aids ◽  
Response Times ◽  
Nonlinear Frequency ◽  
Low Frequencies ◽  
Frequency Compression ◽  
Negative Side ◽  
Minimal Word ◽  
Low Pass ◽  
Negative Side Effects

PurposeFrequency lowering in hearing aids can cause listeners to perceive [s] as [ʃ]. The S-SH Confusion Test, which consists of 66 minimal word pairs spoken by 6 female talkers, was designed to help clinicians and researchers document these negative side effects. This study's purpose was to use this new test to evaluate the hypothesis that these confusions will increase to the extent that low frequencies are altered.MethodTwenty-one listeners with normal hearing were each tested on 7 conditions. Three were control conditions that were low-pass filtered at 3.3, 5.0, and 9.1 kHz. Four conditions were processed with nonlinear frequency compression (NFC): 2 had a 3.3-kHz maximum audible output frequency (MAOF), with a start frequency (SF) of 1.6 or 2.2 kHz; 2 had a 5.0-kHz MAOF, with an SF of 1.6 or 4.0 kHz. Listeners' responses were analyzed using concepts from signal detection theory. Response times were also collected as a measure of cognitive processing.ResultsOverall, [s] for [ʃ] confusions were minimal. As predicted, [ʃ] for [s] confusions increased for NFC conditions with a lower versus higher MAOF and with a lower versus higher SF. Response times for trials with correct [s] responses were shortest for the 9.1-kHz control and increased for the 5.0- and 3.3-kHz controls. NFC response times were also significantly longer as MAOF and SF decreased. The NFC condition with the highest MAOF and SF had statistically shorter response times than its control condition, indicating that, under some circumstances, NFC may ease cognitive processing.ConclusionsLarge differences in the S-SH Confusion Test across frequency-lowering conditions show that it can be used to document a major negative side effect associated with frequency lowering. Smaller but significant differences in response times for correct [s] trials indicate that NFC can help or hinder cognitive processing, depending on its settings.

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