Practical signal‐to‐noise ratio quantification for sensitivity encoding: Application to coronary MR angiography

Yu, Jing; Agarwal, Harsh; Stuber, Matthias; Schär, Michael

doi:10.1002/jmri.22571

Cited by 26 publications

(28 citation statements)

References 33 publications

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“…Moreover, additional images using the spatially selective T 2 Prep with zero time gap were acquired in seven volunteers to test the effect of T gap on the resultant SNR. As quantification of SNR is not straightforward on sensitivity encoding accelerated images (16), additional 3D fast noise scans (∼9 s) with disabled RF excitations and gradients but otherwise identical scan settings were acquired immediately following all the 3D coronary MRA acquisitions for SNR measurements as previously described (17).…”

Section: Methodsmentioning

confidence: 99%

Bacterial chemotaxis toward a NAPL source within a pore‐scale microfluidic chamber

Wang

Long

Ford

2012

Biotech & Bioengineering

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Chemotaxis toward chemical pollutants provides a mechanism for bacteria to migrate to locations of high contamination, which may improve the effectiveness of bioremediation. A microfluidic device was designed to mimic the dissolution of an organic-phase contaminant from a single pore into a larger macropore representing a preferred pathway for microorganisms that are carried along by groundwater flow. The glass windows of the microfluidic device allowed direct image analysis of bacterial distributions within the vicinity of the organic contaminant. Concentrations of chemotactic bacteria P. putida F1 near the organic/aqueous interface were 25% greater than those of a nonchemotactic mutant in the vicinity of toluene for a fluid velocity of 0.5 m/d. For E. coli responding to phenol, the bacterial concentrations were 60% greater than the controls, also at a velocity of 0.5 m/d. Velocities in the macropore were varied over a range from 0.5 to 10 m/d, the lower end of which is typical of groundwater velocities. The accumulation of chemotactic bacteria near the NAPL chemoattractant source decreased as the fluid velocity increased. Good agreement between computer-based simulations, generated using reasonable values of the model parameters, and the experimental data for P. putida strains confirmed the contribution due to chemotaxis. The experimental data for E. coli required a larger chemotactic sensitivity coefficient than that for P. putida, which was consistent with parameter values reported in the literature.

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Section: Methodsmentioning

confidence: 99%

Bacterial chemotaxis toward a NAPL source within a pore‐scale microfluidic chamber

Wang

Long

Ford

2012

Biotech & Bioengineering

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“…All images were reconstructed online with an investigative reconstruction software enabling deblurring of spiral data using an iterative algorithm and a pre‐acquired B 0 field map with dynamic update of the drift in B 0 field due to the thermal response of the gradient system. The online reconstruction time is about 1 min 10 s. The SNR maps were quantitatively calculated as the ratio between the image and the SD derived from the noise data …”

Section: Methodsmentioning

confidence: 99%

Improving the image quality of 3D FLAIR with a spiral MRI technique

Pipe

Ooi

et al. 2019

Magnetic Resonance in Med

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Purpose Fluid‐attenuated inversion recovery (FLAIR) nulls the CSF signal and is widely used in neuro MRI exams. A 3D scan can provide high SNR, contiguous coverage, and reduced sensitivity to through‐plane CSF flow. In this work, a 3D spiral FLAIR technique is proposed to improve the image quality of conventional 3D Cartesian FLAIR. Methods The 3D spiral FLAIR sequence incorporated a spiral‐in/out readout to preserve higher scan efficiency and eliminate off resonance‐induced artifacts observed with a commonly implemented spiral‐out readout, a compensation approach to minimize phase errors due to the concomitant fields accompanying the spiral gradient, and an adapted variable flip angle scheme to preserve scan efficiency and maintain a long and stable echo train. 3D Cartesian and spiral FLAIR (~6 min each) were acquired on a 3 Tesla scanner from 6 subjects (age range: 31‐64 years; mean: 39.5). Two neuroradiologists rated the images in a blinded fashion on a 5‐point scale. The noise performance was assessed quantitatively. Results Compared to 3D Cartesian FLAIR, 3D spiral FLAIR exhibits greater reduction of artifacts from CSF, especially anterior to the brain stem (rated better in 4 cases), artifacts attributed to blood/flow in the deep brain (better or much better in all 6 cases), and superior overall image quality (much better in 5 cases) despite residual susceptibility artifacts near the nasal cavity. Quantitative assessment demonstrates ~1.5× higher average SNR than Cartesian data. Conclusion 3D spiral FLAIR achieves higher SNR, reduced CSF, and blood/flow artifacts, providing an alternative to 3D Cartesian FLAIR for neurological exams.

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“…To quantitatively evaluate the in vivo SNR performance, the approach described in Yu et al was used, which acquires an additional noise data set using identical imaging parameters but with RF and gradients turned off. The noise image was reconstructed in the same way as the normal image, except that for spiral noise data the T 2 ‐decay‐induced signal modulation estimated from the normal image data was used.…”

Section: Methodsmentioning

confidence: 99%