Investigation of acoustic noise on 15 MRI scanners from 0.2 T to 3 T

Price, David L.; Wilde, Janet P. De; Papadaki, Annie; Curran, Jane S.; Kitney, R.I.

doi:10.1002/1522-2586(200102)13:2<288::aid-jmri1041>3.0.co;2-p

Cited by 200 publications

(157 citation statements)

References 9 publications

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“…Currently, both 1.5-and 3.0-T MRI systems are most commonly used in clinical applications. The N2 ghost effect could also depend on the magnetic field strength [16] because the oscillating magnetic field gradients of EPI can result in considerable mechanical vibrations of the gradient coil assembly as the Lorentz forces exerted on the electric currents in the coil increase with increasing magnetic field, causing the N2 ghost [17]. Therefore, we expect that the N2 ghost effect could be less on both 1.5-and 3.0-T MRI systems than on the 4.0-T MRI system if the gradient system is identical.…”

Section: Discussionmentioning

confidence: 99%

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

Jahng

Weiner

Schuff

2008

Magnetic Resonance Imaging

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Diffusion tensor magnetic resonance imaging (DT-MRI) is generally performed using an echo planar imaging (EPI) acquisition to map directional water diffusion. However, the oscillating magnetic field gradients of the EPI acquisition can result in considerable mechanical vibrations, which lead, in turn, to magnetic field fluctuations causing Nyquist ghosting in the EPI data. The objective of this study was to investigate effects of EPI readout gradient modulation frequency, which is directly associated with the EPI readout bandwidth (BW), on the accuracy of DT-MRI measurements in a high magnetic field system. A spherical water phantom was used to study the relationship between the EPI BW and the Nyquist ghost for a spin-echo EPI acquisition with a matrix size of 128×128, complemented by diffusion sensitization gradients of up to b=800 s/mm 2 along six directions for DT-MRI. Nine volunteers (four males and five females) were studied using EPI at different BW acquisitions. Analysis of variance was used to investigate the EPI BW effects. The phantom studies demonstrated a systematic relationship between BWs and the intensities of Nyquist ghosts. In the human brain studies, EPI BW variations substantially corrupted diffusion anisotropy indexes (i.e., fractional anisotropy and relative anisotropy) (F=10.5, P=.0001) but were unrelated to diffusion-encoding directions (F=0.14, P=.98). It was possible to minimize BW dependence (F=1.48, P=.25) by tuning the modulation frequency of the EPI readout gradient. In conclusion, diffusion anisotropic indexes are sensitive to the readout BW of EPI due to associated Nyquist ghosting. However, the effect can be minimized by tuning the modulation frequency of the EPI readout gradient, that is, the EPI BW, to a range outside the harmonics of mechanical gradient vibrations.

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Section: Discussionmentioning

confidence: 99%

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

Jahng

Weiner

Schuff

2008

Magnetic Resonance Imaging

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“…During real-time imaging typically the highest gradient amplitudes are required, which lead to high sound pressure levels (12,13). To protect the ears for both patients and personnel ear protection must be worn at all times, and communication within the RF cabin and between RF cabin and the control room becomes difficult.…”

Section: Accessoriesmentioning

confidence: 99%

MR‐guided intravascular interventions: Techniques and applications

Bock

Wacker

2008

Magnetic Resonance Imaging

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Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities that make it an attractive imaging tool for diagnostic and therapeutic procedures. This tremendous potential of MRI has provided the rationale for increased attention toward MR-guided endovascular interventions. MR guidance has been used recently to navigate endovascular catheters and deliver stents, vena cava filters, embolization materials, and septum closure devices. However, its potential goes beyond just copying existing procedures toward the development of new minimally invasive techniques that cannot be performed with conventional guiding techniques. Because of technical limitations and safety issues associated with some of the currently available devices, a limited number of clinical studies have been performed so far. The overall success for this developing field requires considerable interdisciplinary research within both the interventional and the MR community. Only through a combined effort can this complex technology find its way into clinical practice. This review discusses the hardware and software improvements that have helped to advance endovascular interventions under MR imaging guidance from a pure research tool to become a clinical reality. In addition, technical and safety issues specific to endovascular MR image guidance will be described and practical applications will be shown that take advantage of the benefits of MR for endovascular interventions.

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“…A gradientecho EPI sequence was used with the following parameters: the matrix size of 64 × 64, five transversal slices each 5 mm thick 10 mm apart, and a nominal voxel size of 4×4×5 mm 3 with FOV = 256 × 256 mm 2 . TR and TE were 3 s and 30 ms, respectively with four averages taken.…”

Section: Data Acquisitionsmentioning

confidence: 99%

“…However, in addition to factors of eddy current, echo misalignment, or gradient/receiver miscalibration, the rapidly switching magnetic field gradients of EPI can result in considerable mechanical vibrations which lead in turn to magnetic field fluctuations causing Nyquist (N2) ghosting in the EPI data [1][2][3]. Although many strategies have been invented to reduce N2 ghosts, including gradient compensation [4], timing corrections [5], reference phase corrections [6], and post-processing image restoration [7], none of these methods can entirely eliminate this artifact.…”

Section: Introductionmentioning

confidence: 99%

Influence of selecting EPI readout-encoding bandwidths on arterial spin labeling perfusion MRI

Jahng

Schuff

2009

Magn Reson Mater Phy

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Object The objective of this study was to investigate effects of varying readout bandwidths on the arterial spin labeling (ASL)-perfusion MRI measurements at a high magnetic field MRI system. Materials and methods Brain perfusion studies were performed on nine volunteers (four males, five females) using flow sensitive alternating inversion recovery (FAIR) ASL single-shot echo-planar imaging (EPI)-MRI. To investigate EPI bandwidth effects on the time-series perfusion-weighted imaging (PWI) data, two regions-of-interest (ROI) were placed outside the brain to determine the level of noise and another ROI inside the brain to determine the level of signal. Coefficients of variations (CoV) were calculated for the timeseries PWI data. One-way analysis of variance (ANOVA) was used to investigate voxel-wise differences in the time-series PWI data between two different bandwidth values. Results At the level of ROI, there was no significant effect of changing EPI bandwidths on the time-series PWI data in any of the volunteers (P > 0.031). In contrast, CoV values over the dynamic PWI data varied with depending on selecting EPI bandwidths and voxel-based tests showed that N2 ghosting, modulated by EPI bandwidth, can appear in some brain regions, especially in areas that overlap with the spatial distribution of N2 ghosting artifacts. Conclusions Although N2 ghosting can be reduced by adjusting the bandwidth of EPI on the time-series of PWI data, the effects cannot be entirely eliminated. In particular, N2 ghosting can bias CBF quantification if EPI control scans to determine the equilibrium-state signal are confounded by N2 ghosting. Therefore, careful tuning of the bandwidth of EPI is necessary to avoid artifacts in the ASL signal from N2-ghosting.Keywords Nyquist ghost artifact · Echo-planar imaging · Readout-encoding bandwidth · Arterial spin labeling · Human brain · High field MRI

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Investigation of acoustic noise on 15 MRI scanners from 0.2 T to 3 T

Cited by 200 publications

References 9 publications

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

MR‐guided intravascular interventions: Techniques and applications

Influence of selecting EPI readout-encoding bandwidths on arterial spin labeling perfusion MRI

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