Imaging artifacts at 3.0T

Bernstein, Matt A.; Huston, John; Ward, Heidi A.

doi:10.1002/jmri.20698

Cited by 233 publications

(217 citation statements)

References 89 publications

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“…Phased-arrays exhibit an inhomogeneous reception pattern by having a stronger B1-sensitivity near their surface (18) that can even counteract the central brightening artifact at 3 T (19). For a higher number of receiving array elements the intensity increase in their vicinity becomes so pronounced that a B1 receive-field correction seems appropriate to an investigator interested in the whole sample or in regions located near the coil center.…”

Section: Discussionmentioning

confidence: 99%

Comparison of a 32‐channel with a 12‐channel head coil: Are there relevant improvements for functional imaging?

Kaza

Klose²,

Lotze

2011

Magnetic Resonance Imaging

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Purpose: To evaluate the suitability of a 12-or 32-channel head coil and of a prescan normalization filter for functional magnetic resonance imaging (fMRI) studies at different brain regions.Materials and Methods: fMRI was obtained from 36 volunteers executing a visually instructed motor paradigm using a 12-channel head matrix coil and a 32-channel phased-array head coil with and without prescan normalization filtering at 3 T. The time-course signal-to-noise ratio (tSNR) and the magnitude of functional activation (betavalue, t-value, percent signal change) were statistically compared between experimental conditions for the contralateral primary motor and visual cortex, contralateral thalamus, and ipsilateral anterior cerebellar hemispheres.Results: tSNR was higher overall measuring with the 32-channel array and with prescan normalization. Without filtering, the 32-channel array delivered higher functional activation magnitudes for the visual cortex, whereas the 12-channel array seemed superior in this respect in thalamus and cerebellum. Filtering did not considerably affect the fMRI-activation magnitude detected from the 12-channel coil; its application favored the 32-channel coil at the subcortical and cerebellar locations but disfavored it at the cortical ones. Conclusion:The 32-channel coil detected more fMRI-activation cortically but less subcortically than the 12-channel coil; prescan normalization improved activation parameters only at central brain structures.

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Section: Discussionmentioning

confidence: 99%

Comparison of a 32‐channel with a 12‐channel head coil: Are there relevant improvements for functional imaging?

Kaza

Klose²,

Lotze

2011

Magnetic Resonance Imaging

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“…Hence, the response of the X magnetization, A þ jjbj, and the response of the Y magnetization, jðA À jjbjÞ, are of nearly the same magnitude, but with opposite phase. This phase varies by up to 20 when the flip angle varies. Although this is a small phase error, it may complicate the reconstruction process because its rate of variation along the encoding y-direction can be very large in cases of partial slice effects.…”

Section: Theory Ncpmg Reliance On Flip Anglementioning

confidence: 99%

Slice profile effects on nCPMG SS‐FSE

Gibbons

Roux²,

Pauly

et al. 2017

Magnetic Resonance in Med

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Purpose To determine the effects of the RF refocusing pulse profile on the magnitude of the transverse signal smoothness throughout the echo train in non‐Carr‐Purcell‐Meiboom‐Gill (nCPMG) single‐shot fast spin echo (SS‐FSE) imaging and to design an RF refocusing pulse that provides improved signal stability. Theory and Methods nCPMG SS‐FSE quadratic phase modulation requires sufficiently high and uniform refocusing flip angle to achieve a stable signal. Typically, refocusing pulses used in SS‐FSE sequences are designed for minimum duration to minimize echo spacing and as a consequence have poor selectivity. However, delay‐insensitive variable rate excitation Shinnar‐Le Roux (DV‐SLR) refocusing pulses can achieve both improved selectivity as well as a short duration. This class of RF pulse is compared against a traditional low time‐bandwidth refocusing pulse in a nCPMG SS‐FSE in simulation, phantom, and in vivo. Results DV‐SLR pulses achieve a more stable signal in simulation, phantom, and in vivo cases while maintaining an appropriately short duration as well as not dramatically increasing specific absorption rate (SAR) accumulation. Conclusion The nCPMG SS‐FSE method demonstrates improved robustness when a more selective refocusing pulse is used. Refocusing pulses that use a time‐varying excitation gradient can achieve this selectivity while maintaining short echo spacing. Magn Reson Med 79:430–438, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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“…2); at the same time, increased image artifacts and other limitations make higher field strength scanning technically more challenging. In living organisms, which are comprised of multiple compartments with different physico-chemical properties, artifacts can be generated due to susceptibility and different relaxation properties at the higher field strength [13]. Why certain imaging artifacts are more prominent at the very high field strengths utilized can be best understood in the context of the well-known scaling relationships that describe how SNR, chemical shift, susceptibility variation, specific absorption rate, and RF wavelength vary with increased field strength ( Table 1).…”

Section: Differences Between Small Animal Imaging and Human Mri: Advamentioning

confidence: 99%

MRI in Rodent Models of Brain Disorders

et al. 2011

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Summary: Magnetic resonance imaging (MRI) is a wellestablished tool in clinical practice and research on human neurological disorders. Translational MRI research utilizing rodent models of central nervous system (CNS) diseases is becoming popular with the increased availability of dedicated small animal MRI systems. Projects utilizing this technology typically fall into one of two categories: 1) true "pre-clinical" studies involving the use of MRI as a noninvasive disease monitoring tool which serves as a biomarker for selected aspects of the disease and 2) studies investigating the pathomechanism of known human MRI findings in CNS disease models. Most small animal MRI systems operate at 4.7-11.7 Tesla field strengths. Although the higher field strength clearly results in a higher signalto-noise ratio, which enables higher resolution acquisition, a variety of artifacts and limitations related to the specific absorption rate represent significant challenges in these experiments. In addition to standard T1-, T2-, and T2*-weighted MRI methods, all of the currently available advanced MRI techniques have been utilized in experimental animals, including diffusion, perfusion, and susceptibility weighted imaging, functional magnetic resonance imaging, chemical shift imaging, heteronuclear imaging, and 1 H or 31 P MR spectroscopy. Selected MRI techniques are also exclusively utilized in experimental research, including manganese-enhanced MRI, and cell-specific/molecular imaging techniques utilizing negative contrast materials. In this review, we describe technical and practical aspects of small animal MRI and provide examples of different MRI techniques in anatomical imaging and tract tracing as well as several models of neurological disorders, including inflammatory, neurodegenerative, vascular, and traumatic brain and spinal cord injury models, and neoplastic diseases.

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Imaging artifacts at 3.0T

Cited by 233 publications

References 89 publications

Comparison of a 32‐channel with a 12‐channel head coil: Are there relevant improvements for functional imaging?

Comparison of a 32‐channel with a 12‐channel head coil: Are there relevant improvements for functional imaging?

Slice profile effects on nCPMG SS‐FSE

MRI in Rodent Models of Brain Disorders

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