Non-Cartesian sampled centric scan SPRITE imaging with magnetic field gradient and B0(t) field measurements for MRI in the vicinity of metal structures

Han, Hua; Green, Derrick; Ouellette, Matthew; MacGregor, R.; Balcom, Bruce J.

doi:10.1016/j.jmr.2010.06.012

Cited by 15 publications

(16 citation statements)

References 35 publications

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“…In our recent work on MRI inside metal vessels (27), the MFGM method (24) was employed to measure gradient waveforms for non-Cartesian sampled centric scan SPRITE imaging. For clinical MRI scanners however special care should be taken when implementing pure phase encode approaches.…”

Section: Discussionmentioning

confidence: 99%

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Direct measurement of magnetic field gradient waveforms

Han¹,

Ouriadov²,

Fordham³

et al. 2010

Concepts Magnetic Resonance

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As eddy currents increase with gradient amplitude and faster slew rate, they have become a greater problem with the advent of higher-performance gradients in modern MRI scanners. Success in eddy current reduction techniques such as active gradient shielding and waveform pre-emphasis, however, require that the residual eddy currents must be measured with high accuracy for image improvement. Traditional MR based gradient calibration techniques, whether based on an entire FID or a gradient echo, measure the integral of gradient waveforms. We have however previously proposed a different category of methods, which employ pure phase encode FIDs and have proven advantageous in directly measuring the gradient waveforms. In this article, we review the basis of these pure phase encode methods. In keeping with the instructional nature of CMRA, we undertake this review by describing specific experiments and the line of the thought behind the experiments. The pure phase encode approach is sensitive to low amplitude gradients (0.001-1 G/cm), and also permits measurement of high amplitude gradients (10-300 G/cm). The inverse Fourier transform permits ready understanding of these pure phase encode methods. The accuracy of pure phase encode gradient measurement is significantly improved by a multiple FID point acquisition, which permits high temporal resolution of the gradient waveform. The accuracy of gradient measurements is also analyzed and improved through elimination of potential artifacts. As one example of the capability of these methods, waveform measurements were undertaken to reduce the repetition time TR for centric scan SPRITE experiments.

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Section: Discussionmentioning

confidence: 99%

“…It relies on a small RF probe and associated test sample to spatially monitor the gradient behavior within the sample space, within the imaging RF coil. The MFGM method (24) also permits multiple axes to be measured simultaneously with acquisition times proportional to the number of gradient axes (27).…”

Section: Introductionmentioning

confidence: 99%

Direct measurement of magnetic field gradient waveforms

Han¹,

Ouriadov²,

Fordham³

et al. 2010

Concepts Magnetic Resonance

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“…Fully phase-encoded methods avoid artifacts related to frequency encoding (16)(17)(18)(19)(20) but require extraordinarily long scan times. One technique uses a spectrally resolved, fully phase-encoded (SR-FPE) 3D FSE acquisition scheme that phase-encodes all three spatial dimensions while collecting temporal data across each spin echo (16).…”

Section: Introductionmentioning

confidence: 99%

Accelerating fully phase‐encoded MRI near metal using multiband radiofrequency excitation

Artz

Wiens

Smith

et al. 2016

Magnetic Resonance in Med

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Purpose To develop a multiband radiofrequency (RF) excitation strategy for simultaneous excitation of multiple RF offsets to accelerate fully phase-encoded imaging near metallic prostheses. Methods Multiband RF excitation was designed and incorporated into a spectrally resolved fully phase-encoded (SR-FPE) imaging scheme. A triband (−6, 0, 6 kHz) acquisition was compared with three separate single-band acquisitions at the corresponding RF offsets with a phantom containing the head of a hip prosthesis. In vivo multiband data with continuous spectral coverage were acquired in the knee of a healthy volunteer with the head of a hip prosthesis placed posteriorly and in a volunteer with a total knee prosthetic implant. Results Phantom images acquired with triband excitation were essentially identical to the composite of three single-band excitations, but with an acceleration factor of three. In vivo multiband images of the healthy knee with adjacent metal demonstrated very good depiction of knee anatomy. In vivo images of the total knee replacement were successfully acquired, allowing visualization of native tissue with far less signal dropout than 2D-FSE. Conclusions FPE imaging with multiband excitation is feasible in the presence of extreme off-resonance. This approach can reduce scan time and/or increase off-resonance coverage, enabling in vivo FPE imaging near metallic prostheses over a broad off-resonance spectrum.

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“…To address artifacts near metal due to frequency encoding, which occur even in MAVRIC/SEMAC methods , fully phase‐encoded techniques (FPE) have been developed . These methods perform phase‐encoding in all three spatial dimensions to completely avoid frequency encoding artifacts near metal.…”

Section: Introductionmentioning

confidence: 99%

Accelerating sequences in the presence of metal by exploiting the spatial distribution of off‐resonance

Smith

Artz

Koch

et al. 2014

Magnetic Resonance in Med

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Purpose To demonstrate feasibility of exploiting the spatial distribution of off-resonance surrounding metallic implants for accelerating multispectral imaging techniques. Theory Multispectral imaging (MSI) techniques perform time-consuming independent 3D acquisitions with varying RF frequency offsets to address the extreme off-resonance from metallic implants. Each off-resonance bin provides a unique spatial sensitivity that is analogous to the sensitivity of a receiver coil, and therefore provides a unique opportunity for acceleration. Methods Fully sampled MSI was performed to demonstrate retrospective acceleration. A uniform sampling pattern across off-resonance bins was compared to several adaptive sampling strategies using a total hip replacement phantom. Monte Carlo simulations were performed to compare noise propagation of two of these strategies. With a total knee replacement phantom, positive and negative off-resonance bins were strategically sampled with respect to the B0 field to minimize aliasing. Reconstructions were performed with a parallel imaging framework to demonstrate retrospective acceleration. Results An adaptive sampling scheme dramatically improved reconstruction quality, which was supported by the noise propagation analysis. Independent acceleration of negative and positive off-resonance bins demonstrated reduced overlapping of aliased signal to improve the reconstruction. Conclusion This work presents the feasibility of acceleration in the presence of metal by exploiting the spatial sensitivities of off-resonance bins.

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Non-Cartesian sampled centric scan SPRITE imaging with magnetic field gradient and B0(t) field measurements for MRI in the vicinity of metal structures

Cited by 15 publications

References 35 publications

Direct measurement of magnetic field gradient waveforms

Direct measurement of magnetic field gradient waveforms

Accelerating fully phase‐encoded MRI near metal using multiband radiofrequency excitation

Accelerating sequences in the presence of metal by exploiting the spatial distribution of off‐resonance

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