Beamformer enhancement by post-processing for improved spatial resolution and signal-to-noise ratio

2008 ◽  
Author(s):  
Kevin Owen ◽  
Drake A. Guenther ◽  
William F. Walker
Keyword(s):  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Post Processing ◽  
Signal To Noise ◽  
Noise Ratio

Spatial resolution and signal-to-noise ratio in x-ray imaging

2019 ◽  
Author(s):  
Timur Gureyev ◽  
David M. Paganin ◽  
Alex Kozlov ◽  
Harry Quiney
Keyword(s):  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
X Ray ◽  
X Ray Imaging ◽  
Noise Ratio

k-Space filtering in 2D gradient-echo breath-hold hyperpolarized3He MRI: Spatial resolution and signal-to-noise ratio considerations

2002 ◽  
Vol 47 (4) ◽  
pp. 687-695 ◽  
Author(s):  
Jim M. Wild ◽  
Martyn N.J. Paley ◽  
Magalie Viallon ◽  
Wolfgang G. Schreiber ◽  
Edwin J.R. van Beek ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Breath Hold ◽  
Gradient Echo ◽  
Signal To Noise ◽  
Noise Ratio

scholarly journals Novel Configurations of Ultrahigh Frequency (≤600 MHz) Analog Frontend for High Resolution Ultrasound Measurement

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2598
Author(s):  
Min Kim ◽  
Jinhyoung Park ◽  
Qifa Zhou ◽  
Koping Shung
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Ultrahigh Frequency ◽  
Ultrasound Measurement ◽  
Functional Responses ◽  
Signal To Noise ◽  
Coded Excitation ◽  
Noise Ratio ◽  
The Difference

In this article, an approach to designing and developing an ultrahigh frequency (≤600 MHz) ultrasound analog frontend with Golay coded excitation sequence for high resolution imaging applications is presented. For the purpose of visualizing specific structures or measuring functional responses of micron-sized biological samples, a higher frequency ultrasound is needed to obtain a decent spatial resolution while it lowers the signal-to-noise ratio, the difference in decibels between the signal level and the background noise level, due to the higher attenuation coefficient. In order to enhance the signal-to-noise ratio, conventional approach was to increase the transmit voltage level. However, it may cause damaging the extremely thin piezoelectric material in the ultrahigh frequency range. In this paper, we present a novel design of ultrahigh frequency (≤600 MHz) frontend system capable of performing pseudo Golay coded excitation by configuring four independently operating pulse generators in parallel and the consecutive delayed transmission from each channel. Compared with the conventional monocycle pulse approach, the signal-to-noise ratio of the proposed approach was improved by 7–9 dB without compromising the spatial resolution. The measured axial and lateral resolutions of wire targets were 16.4 µm and 10.6 µm by using 156 MHz 4 bit pseudo Golay coded excitation, respectively and 4.5 µm and 7.7 µm by using 312 MHz 4 bit pseudo Golay coded excitation, respectively.

An Optimum Imaging Scheme for IVUS Arrays: Eccentric Cylinder Wave Compounding

2019 ◽  
Vol 41 (3) ◽  
pp. 173-187 ◽  
Author(s):  
Mingxia Li ◽  
Zhihua Feng
Keyword(s):  
Intravascular Ultrasound ◽  
Integrated Circuit ◽  
Signal To Noise Ratio ◽  
Post Processing ◽  
Signal To Noise ◽  
Eccentric Cylinder ◽  
Noise Ratio ◽  
Optimum Imaging ◽  
Eccentric Distance

With the development of integrated circuit (IC) technologies, complex transmitting and receiving circuits can be integrated into miniature intravascular ultrasound (IVUS) catheters, making it possible to adopt better synthesizing schemes for better imaging. Eccentric cylinder wave compounding should be an optimum synthesizing scheme for the small size cylinder shaped catheter. Eccentric cylinder waves centered at different points are emitted, signals are collected after each emission, and images can be synthesized with easy post processing. Detailed analyses about resolution and grating lobes were made; the optimum eccentric distance was determined. Simulations were done to examine the resolution, signal-to-noise ratio, and resistance to crosstalk and nonuniformity of arrays. Dual apodization and magnitude-based deconvolution were applied to further improve the results.

scholarly journals X-ray shadowgraphy applications in ablatively accelerated planar foil studies

1992 ◽  
Vol 10 (4) ◽  
pp. 685-688 ◽  
Author(s):  
V. A. Bolotin ◽  
I. N. Burdonsky ◽  
V. V. Gavrilov ◽  
A. Yu. Gol'tsov ◽  
E. V. Zhuzhukalo ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Spatial Resolution ◽  
Spectral Range ◽  
Focal Spot ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Plasma Flows ◽  
X Ray ◽  
Noise Ratio ◽  
Drive Laser Pulse

The article reviews experiments on flash X radiography of laser-accelerated foils. The spatial resolution, sensitivity, spectral range, and signal-to-noise ratio of measurements were carefully optimized and characterized. The method was used at the Mishen facility to measure a distribution of mass ablative rate across the focal spot and for observation of the transverse plasma flows during the drive laser pulse.

scholarly journals The effect of spatial resolution on the reproducibility of diffusion imaging when controlled signal to noise ratio

2019 ◽  
Vol 42 (4) ◽  
pp. 268-276 ◽  
Author(s):  
Yao-Liang Chen ◽  
Yu-Jen Lin ◽  
Sung-Han Lin ◽  
Chih-Chien Tsai ◽  
Yu-Chun Lin ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Diffusion Imaging ◽  
Signal To Noise ◽  
Noise Ratio

scholarly journals Stable, Intelligible Ultrasonic Strain Imaging

Ultrasound ◽  
2008 ◽  
Vol 16 (4) ◽  
pp. 187-192 ◽  
Author(s):  
Andrew Gee ◽  
Joel Lindop ◽  
Graham Treece ◽  
Richard Prager ◽  
Susan Freeman
Keyword(s):  
Breast Biopsy ◽  
Signal To Noise Ratio ◽  
Strain Imaging ◽  
Time Averaging ◽  
Post Processing ◽  
Signal To Noise ◽  
Processing Strategies ◽  
Improved Stability ◽  
Noise Ratio

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: The post-processing strategy is evaluated qualitatively on scans of a breast biopsy phantom and in vivo head and neck examinations. Strain images processed in this manner are observed to benefit from improved stability and signal-to-noise ratio. There are, however, limitations. In unusual though conceivable circumstances, the normalization procedure might suppress genuine stiffness variations evident in the unprocessed strain images. In different circumstances, the raw strain images might fail to capture significant stiffness variations, a situation that no amount of post-processing can improve. Conclusion: The clinical utility of freehand quasistatic strain imaging can be improved by normalization, precision-weighted pixel-level persistence and precision-based display. The resulting images are stable and generally exhibit a better signal-to-noise ratio than any of the original, unprocessed strain images.

A Least-Squares Strain Estimator for Elastography

1997 ◽  
Vol 19 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Faouzi Kallel ◽  
Jonathan Ophir
Keyword(s):  
Least Squares ◽  
Spatial Resolution ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Simulated Data ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Gel Phantom

A least-squares strain estimator (LSQSE) for elastography is proposed. It is shown that with such an estimator, the signal-to-noise ratio in an elastogram ( SNRe) is significantly improved. This improvement is illustrated theoretically using a modified strain filter and experimentally using a homogeneous gel phantom. It is demonstrated that the LSQSE results in an increase of the elastographic sensitivity (smallest strain that could be detected), thereby increasing the strain dynamic range. Using simulated data, it is shown that a tradeoff exists between the improvement in SNRe and the reduction of strain contrast and spatial resolution.

scholarly journals Signal and noise in helioseismic holography

2018 ◽  
Vol 620 ◽  
pp. A136 ◽  
Author(s):  
Laurent Gizon ◽  
Damien Fournier ◽  
Dan Yang ◽  
Aaron C. Birch ◽  
Hélène Barucq
Keyword(s):  
Spatial Resolution ◽  
Green's Function ◽  
Sound Speed ◽  
Signal To Noise Ratio ◽  
Solar Interior ◽  
Solar Oscillations ◽  
Signal To Noise ◽  
Holographic Image ◽  
Image Intensity ◽  
Noise Ratio

Context. Helioseismic holography is an imaging technique used to study heterogeneities and flows in the solar interior from observations of solar oscillations at the surface. Holographic images contain noise due to the stochastic nature of solar oscillations. Aims. We aim to provide a theoretical framework for modeling signal and noise in Porter–Bojarski helioseismic holography. Methods. The wave equation may be recast into a Helmholtz-like equation, so as to connect with the acoustics literature and define the holography Green’s function in a meaningful way. Sources of wave excitation are assumed to be stationary, horizontally homogeneous, and spatially uncorrelated. Using the first Born approximation we calculated holographic images in the presence of perturbations in sound-speed, density, flows, and source covariance, as well as the noise level as a function of position. This work is a direct extension of the methods used in time-distance helioseismology to model signal and noise. Results. To illustrate the theory, we compute the holographic image intensity numerically for a buried sound-speed perturbation at different depths in the solar interior. The reference Green’s function is obtained for a spherically-symmetric solar model using a finite-element solver in the frequency domain. Below the pupil area on the surface, we find that the spatial resolution of the holographic image intensity is very close to half the local wavelength. For a sound-speed perturbation of size comparable to the local spatial resolution, the signal-to-noise ratio is approximately constant with depth. Averaging the image intensity over a number N of frequencies above 3 mHz increases the signal-to-noise ratio by a factor nearly equal to the square root of N. This may not be the case at lower frequencies, where large variations in the holographic signal are due to the contributions from the long-lived modes of oscillation.

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