Hadamard‐encoding combined with two‐dimensional‐selective radiofrequency excitations for flexible and efficient acquisitions of multiple voxels in MR spectroscopy

Busch, Martin G.; Finsterbusch, Jürgen

doi:10.1002/jmri.23521

Cited by 2 publications

(2 citation statements)

References 20 publications

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“…With appropriate permutations, the individual signal can be identified. This has been demonstrated for the simultaneous acquisition of multiple target regions (26).…”

Section: Discussionmentioning

confidence: 99%

Eliminating side excitations in PROPELLER‐based 2D‐selective RF excitations

Busch

Finsterbusch

2012

Magnetic Resonance in Med

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Recently, spatially two-dimensional selective radiofrequency excitations based on the PROPELLER trajectory have been presented and were applied to minimize partial volume effects in single-voxel MR spectroscopy. Thereby, residual side excitations appeared due to limitations of the Voronoi diagram that was used to consider the nonconstant sampling density, and trajectory distortions caused by eddy currents varying between the differently rotated blades. In this extension, one of the refocusing radiofrequency pulses of a PRESS-based pulse sequence is applied in the blip direction of each segment to eliminate the side excitations. This corresponds to an infinitely dense sampling of the blade and the required sampling density correction can easily be calculated. Thus, signal contributions from outside the desired region-of-interest are completely avoided. The feasibility of this approach to acquire single-voxel MR spectra of anatomically defined regions-of-interest is demonstrated in the human brain in vivo on a 3T whole-body MR system.

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“…With appropriate permutations, the individual signal can be identified. This has been demonstrated for the simultaneous acquisition of multiple target regions (26).…”

Section: Discussionmentioning

confidence: 99%

Eliminating side excitations in PROPELLER‐based 2D‐selective RF excitations

Busch

Finsterbusch

2012

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

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“…These works explore RF pulse design and applications such as inner volume imaging and the suppression of artifacts originating from tissue outside the ROI . Multidimensional SSE is also an active field of research in single‐voxel targeted MR spectroscopy, where it has been incorporated using tailored excitation with segmented RF pulses and with additional PEX .…”

mentioning

confidence: 99%

PexLoc—Parallel excitation using local encoding magnetic fields with nonlinear and nonbijective spatial profiles

Haas

Ullmann

Schneider

et al. 2012

Magnetic Resonance in Med

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With the recent proposal of using magnetic fields that are nonlinear by design for spatial encoding, new flexibility has been introduced to MR imaging. The new degrees of freedom in shaping the spatially encoding magnetic fields (SEMs) can be used to locally adapt the imaging resolution to features of the imaged object, e.g., anatomical structures, to reduce peripheral nerve stimulation during in vivo experiments or to increase the gradient switching speed by reducing the inductance of the coils producing the SEMs and thus accelerate the imaging process. In this work, the potential of nonlinear and nonbijective SEMs for spatial encoding during transmission in multidimensional spatially selective excitation is explored. Methods for multidimensional spatially selective excitation radiofrequency pulse design based on nonlinear encoding fields are introduced, and it is shown how encoding ambiguities can be resolved using parallel transmission. In simulations and phantom experiments, the feasibility of selective excitation using nonlinear, nonbijective SEMs is demonstrated, and it is shown that the spatial resolution with which the target distribution of the transverse magnetization can be realized varies locally. Thus, the resolution of the target pattern can be increased in some regions compared with conventional linear encoding. Furthermore, experimental proof of principle of accelerated two-dimensional spatially selective excitation using nonlinear SEMs is provided in this study.

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Hadamard‐encoding combined with two‐dimensional‐selective radiofrequency excitations for flexible and efficient acquisitions of multiple voxels in MR spectroscopy

Cited by 2 publications

References 20 publications

Eliminating side excitations in PROPELLER‐based 2D‐selective RF excitations

Eliminating side excitations in PROPELLER‐based 2D‐selective RF excitations

PexLoc—Parallel excitation using local encoding magnetic fields with nonlinear and nonbijective spatial profiles

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