Four dimensional spectral‐spatial fat saturation pulse design

Zhang, Feng; Nielsen, Jon‐Fredrik; Noll, Douglas C.

doi:10.1002/mrm.25076

Cited by 8 publications

(26 citation statements)

References 31 publications

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“…Spatially tailored RF excitation has a range of applications in MRI, including B1 shimming [1]–[6], reduced FOV excitation [7]–[13], susceptibility artifact correction [14]–[18], and fat suppression [19], [20]. The task of designing time-varying RF and gradient waveforms for a desired target excitation pattern poses a non-linear, non-convex, constrained optimization problem with relatively large problem size that is difficult to solve directly.…”

Section: Introductionmentioning

confidence: 99%

Joint Design of Excitation k-Space Trajectory and RF Pulse for Small-Tip 3D Tailored Excitation in MRI

Sun¹,

Fessler²,

Noll³

et al. 2016

IEEE Trans. Med. Imaging

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We propose a new method for the joint design of k-space trajectory and RF pulse in 3D small-tip tailored excitation. Designing time-varying RF and gradient waveforms for a desired 3D target excitation pattern in MRI poses a non-linear, non-convex, constrained optimization problem with relatively large problem size that is difficult to solve directly. Existing joint pulse design approaches are therefore typically restricted to predefined trajectory types such as EPI or stack-of-spirals that intrinsically satisfy the gradient maximum and slew rate constraints and reduce the problem size (dimensionality) dramatically, but lead to suboptimal excitation accuracy for a given pulse duration. Here we use a 2nd-order B-spline basis that can be fitted to an arbitrary k-space trajectory, and allows the gradient constraints to be implemented efficiently. We show that this allows the joint optimization problem to be solved with quite general k-space trajectories. Starting from an arbitrary initial trajectory, we first approximate the trajectory using B-spline basis, and then optimize the corresponding coefficients. We evaluate our method in simulation using four different k-space initializations: stack-of-spirals, SPINS, KT-points, and a new method based on KT-points. In all cases, our approach leads to substantial improvement in excitation accuracy for a given pulse duration. We also validated our method for inner-volume excitation using phantom experiments. The computation is fast enough for online applications.

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Section: Introductionmentioning

confidence: 99%

Joint Design of Excitation k-Space Trajectory and RF Pulse for Small-Tip 3D Tailored Excitation in MRI

Sun¹,

Fessler²,

Noll³

et al. 2016

IEEE Trans. Med. Imaging

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“…The fat sat and MT part ( S 1 ) with the FSMT‐pulse ( P 0 ) is added prior to the regular excitation pulse ( P 1 ) of SPGR ( S 2 ) in each repetition, and both S 1 and S 2 have a gradient crusher, i.e., C 1 and C 2 . This 2D version of FSMT‐SPGR uses a 3D FSMT‐pulse that is tailored to the B 0 / B 1 field using the same method proposed in , and it uses repeated 2D spiral‐out trajectories to cover the 3D spectral‐spatial k‐space . The 3D version of the FSMT‐SPGR uses the same FSMT‐pulse used in .…”

Section: Theorymentioning

confidence: 99%

“…Moreover, the fat sat pulse is long in low field scanners, limiting the minimum T R for some fast MRI sequences. These problems have been mitigated using a 4D tailored spectral‐spatial fat sat pulse proposed in . That fat sat pulse is robust to B 0 / B 1 inhomogeneity and more time‐efficient than the standard fat sat pulse.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we propose to apply the n ‐dimensional tailored spectral‐spatial fat sat pulse proposed in to SSI sequences, including SPGR and STFR, to produce fat suppressed MTC images. In the context of this article, such pulse is referred to as “fat sat and MT contrast pulse” (FSMT‐pulse).…”

Section: Introductionmentioning

confidence: 99%

“…The major contribution of this work is the combination of FSMT‐pulse and SSI sequences. FSMT‐pulse has short pulse length and very high power efficiency . Its pulse length mitigates the issue of limited T R in steady‐state imaging, and the high power efficiency contributes to MT contrasts.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Simultaneous fat saturation and magnetization transfer contrast imaging with steady‐state incoherent sequences

Zhang

Nielsen

Swanson

et al. 2014

Magnetic Resonance in Med

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Purpose This work combines an n-dimensional (nD) fat sat(uration) RF pulse with steady-state incoherent (SSI) pulse sequences, e.g., spoiled Gradient echo sequence, to simultaneously produce B0 insensitive fat suppression and magnetization transfer (MT) contrast. This pulse is then referred to as ”fat sat and MT contrast pulse” (FSMT-pulse). Theory We discuss the features of the FSMT-pulse and the MT sensitivities of the SSI sequences when combining with fat sat. Moreover, we also introduce an adapted RF spoiling scheme for SSI sequences with fat sat. Methods Simulations and phantom experiments were conducted to demonstrate the adapted RF spoiling. Fat suppression and MT effects are shown in 3T phantom experiments and in-vivo experiments, including brain imaging, cartilage imaging and angiography. Results To ensure that the sequence reaches steady state, the adapted RF spoiling is required for fat-sat SSI sequences. FSMT-pulse works robustly with field inhomogeneity and also produces MT contrasts. Conclusion SSI sequences with FSMT-pulse and adapted RF spoiling can robustly produce fat suppressed and MT contrast images in the presence of field inhomogeneity.

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Parallel transmit optimized 3D composite adiabatic spectral‐spatial pulse for spectroscopy

Auerbach

Kobayashi

et al. 2021

Magnetic Resonance in Med

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To develop a 3D composite adiabatic spectral-spatial pulse for refocusing in spin-echo spectroscopy acquisitions and to compare its performance against standard acquisition methods. Methods: A 3D composite adiabatic pulse was designed by modulating a train of parallel transmit-optimized 2D subpulses with an adiabatic envelope. The spatial and spectral profiles were simulated and validated by experiments to demonstrate the feasibility of the design in both single and double spin-echo spectroscopy acquisitions. Phantom and in vivo studies were performed to evaluate the pulse performance and compared with semi-LASER with respect to localization performance, sequence timing, signal suppression, and specific absorption rate. Results: Simultaneous 2D spatial localization with water and lipid suppression was achieved with the designed refocusing pulse, allowing high-quality spectra to be acquired with shorter minimum TE/TR, reduced SAR, as well as adaptation to spatially varying B 0 and B + 1 field inhomogeneities in both prostate and brain studies. Conclusion: The proposed composite pulse can serve as a more SAR efficient alternative to conventional localization methods such as semi-LASER at ultrahigh field for spin echo-based spectroscopy studies. Subpulse parallel-transmit optimization provides the flexibility to manage the tradeoff among multiple design criteria to accommodate different field strengths and applications.

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Four dimensional spectral‐spatial fat saturation pulse design

Cited by 8 publications

References 31 publications

Joint Design of Excitation k-Space Trajectory and RF Pulse for Small-Tip 3D Tailored Excitation in MRI

Joint Design of Excitation k-Space Trajectory and RF Pulse for Small-Tip 3D Tailored Excitation in MRI

Simultaneous fat saturation and magnetization transfer contrast imaging with steady‐state incoherent sequences

Parallel transmit optimized 3D composite adiabatic spectral‐spatial pulse for spectroscopy

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