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

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

scholarly journals Parametric analysis of the spatial resolution and signal-to-noise ratio in super-resolved spatiotemporally encoded (SPEN) MRI

2013 ◽  
Vol 72 (2) ◽  
pp. 418-429 ◽  
Author(s):  
Noam Ben-Eliezer ◽  
Yoav Shrot ◽  
Lucio Frydman ◽  
Daniel K. Sodickson
Keyword(s):  
Spatial Resolution ◽  
Parametric Analysis ◽  
Signal To Noise Ratio ◽  
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.

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

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.

scholarly journals Optimalisasi Citra Axial Sequence T2 Gradient Echo Dengan Variasi Bandwidth Dan Time Echo Pada MRI Shoulder Untuk Mengurangi Susceptibility Artifacts Dan Chemical Shift

2018 ◽  
Vol 5 (2) ◽  
pp. 40-49
Author(s):  
Akhmad Muzamil ◽  
Nur Vita Indri ◽  
Suryani Dyah Astuti ◽  
Tri Anggono Prijo
Keyword(s):  
Chemical Shift ◽  
Signal To Noise Ratio ◽  
Region Of Interest ◽  
Gradient Echo ◽  
Signal To Noise ◽  
Susceptibility Artifacts ◽  
Axial Gradient ◽  
Noise Ratio ◽  
Mri Shoulder

Penelitian ini bertujuan untuk mengetahui pengaruh Bandwidth (BW) dan Time Echo (TE) pada MRI Shoulder serta mengetahui nilai variasi Bandwidth dan Time Echo yang optimal untuk mengurangi Susceptibility Artifacts dan Chemical Shift. Penelitian ini di lakukan di Rumah Sakit Umum Haji Surabaya dengan menggunakan Pesawat MRI 1,5 Tesla. Penelitian ini  menggunakan varaisi Bandwidth 170 Hz/Px, 190 Hz/Px dan 210 Hz/Px serta menggunakan variasi TE 16 ms dan 20 ms pada pembobotan T2 Medic potongan axial terhadap 4 pasien. Analisa data dilakukan secara kuantitatif dengan menggunakan metode Region of Interest (ROI) pada komputer MRI kemudian dilakukan analisis Signal to Noise Ratio (SNR) dan Contrast to Noise Ratio (CNR) serta analisis terhadap Susceptibility  Artifacts dan Chemical Shift. Variasi Time Echo dan bandwidth berpengaruh signifikan terhadap nilai SNR dan CNR pada hasil citra T2 Axial Gradient Echo MRI Shoulder. Pengaruh kedua variasi tersebut adalah semakin kecil nilai TE dan BW didapatkan SNR yang meningkat. Jika TE diperbesar maka didapatkan CNR yang meningkat. Kualitas citra optimal yang dapat menghasilkan keadaan patologis ditentukan dengan meningkatnya nilai CNR dan nilai artefak yang menurun. Sehingga pada penelitian ini kombinasi antara 2 variabel tersebut dapat menentukan citra optimal pada TE 20ms dan BW 210 Hz/Px.

scholarly journals Multi-source high-resolution satellite products in Yangtze Estuary: cross-comparisons and impacts of signal-to-noise ratio and spatial resolution

2019 ◽  
Vol 27 (5) ◽  
pp. 6426 ◽  
Author(s):  
Rugang Tang ◽  
Fang Shen ◽  
Yanqun Pan ◽  
Kevin Ruddick ◽  
Pei Shang
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Yangtze Estuary ◽  
Signal To Noise ◽  
Noise Ratio
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