Parameter relations for the Shinnar-Le Roux selective excitation pulse design algorithm (NMR imaging)

Pauly, John M.; Roux, Patrick Le; Nishimura, Dwight G.; Macovski, Albert

doi:10.1109/42.75611

Cited by 731 publications

(796 citation statements)

References 10 publications

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“…Due to hardware restrictions on the MR scanner, adiabatic inversion pulses shorter than 5 msec were not feasible. Further improvement can be achieved utilizing the Shinnar-Le Roux algorithm (20,21) to create shorter 180°pulses with accurate inversion profiles. Nonetheless, the presented sequence provides sufficient signal intensity to image 10-mm slices.…”

Section: Discussionmentioning

confidence: 99%

Assessment of pulmonary perfusion in a single shot using SEEPAGE

Fischer¹,

Pracht²,

Arnold³

et al. 2007

Magnetic Resonance Imaging

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Purpose: To present a single-shot perfusion imaging sequence that does not require contrast agents or a subtraction of a tag and a control image to create the perfusionweighted contrast. The proposed method is based on SEEPAGE. Materials and Methods:Experiments with healthy volunteers were performed to qualitatively and quantitatively obtain pulmonary perfusion values in coronal as well as sagittal orientation. In addition, a first experiment with a lung cancer patient was performed to explore the potentials of SEEPAGE in a clinical application. Results:All experiments clearly showed a perfusionweighted contrast, providing clinical quality images with high spatial resolution. The quantified perfusion rates were consistent in the different imaging orientations and covered the interval of 1.00 -4.00 mL/min/mL. In addition, the gravitational dependence of pulmonary perfusion, the influence of adiabatic pulse duration on signal intensity, and the tracer saturation effect were examined. In the patient examination the presented technique provided additional information of the lung deficiency compared to a conventional anatomical image.Conclusion: SEEPAGE has proved to be a robust and reproducible technique for obtaining perfusion-weighted images in a single measurement and for quantifying pulmonary perfusion using an additional reference scan. Furthermore, the proposed method shows promise for future clinical application.

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Section: Discussionmentioning

confidence: 99%

Assessment of pulmonary perfusion in a single shot using SEEPAGE

Fischer¹,

Pracht²,

Arnold³

et al. 2007

Magnetic Resonance Imaging

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“…Mice were maintained and handled under protocols approved by the Weizmann Institute's Animal Care and Use Committee. All radiofrequency pulses used in the various sequences were designed using the Shinnar-LeRoux algorithm (30). Calculations and postexperimental data processing were implemented using customwritten MatLab (The MathWorks Inc., Natick, MA) software packages.…”

Section: Methodsmentioning

confidence: 99%

Super‐resolved spatially encoded single‐scan 2D MRI

Ben‐Eliezer

Irani

Frydman

2010

Magnetic Resonance in Med

129

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Single-scan MRI underlies a wide variety of clinical and research activities, including functional and diffusion studies. Most common among these ''ultrafast'' MRI approaches is echo-planar imaging. Notwithstanding its proven success, echo-planar imaging still faces a number of limitations, particularly as a result of susceptibility heterogeneities and of chemical shift effects that can become acute at high fields. The present study explores a new approach for acquiring multidimensional MR images in a single scan, which possesses a higher built-in immunity to this kind of heterogeneity while retaining echo-planar imaging's temporal and spatial performances. This new protocol combines a novel approach to multidimensional spectroscopy, based on the spatial encoding of the spin interactions, with image reconstruction algorithms based on super-resolution principles. Single-scan two-dimensional MRI examples of the performance improvements provided by the resulting imaging protocol are illustrated using phantom-based and in vivo experiments. Magn Reson Med 63:1594-1600, 2010. V C 2010 Wiley-Liss, Inc.Key words: single-scan imaging; super-resolution; ultrafast MRI; spatial encoded imaging; susceptibility compensation; EPI The last decades have witnessed a continuous growth in the use of single-scan MRI, both for clinical and research applications (1,2). These ''ultrafast'' protocols play an essential role in experiments demanding high temporal resolution like functional MRI (3-5); they also constitute integral components in high-dimensionality experiments such as diffusion tensor imaging (6). Foremost among the sequences enabling the acquisition of MR images in a single scan stands echo-planar imaging (EPI) (7), with its many different variants (8,9). EPI relies on a single excitation of all spins within the volume to be examined, followed by repetitive gradient oscillations that scan, in a single continuous acquisition, large regions of the image conjugate (k-space) domain. The rðrÞ spin density profile being sought is then retrieved by a numerical Fourier transform (FT) of the digitized information. Notwithstanding their real-time image-gathering capabilities, EPI-based protocols are still challenged by the relatively long data sampling times that they involve. These are ca. an order of magnitude longer than those typically involved in multiscan MRI and expose the protocol to progressive temporal artifacts arising from susceptibility variations, from unfavorable shimming conditions, or from chemical shift heterogeneities. These in turn put practical limitations to the organs and/or conditions that can be studied using ultrafast MRI protocols.By contrast to EPI's reliance on contributions arising simultaneously from the entire sample, we have recently begun exploring the consequences of relying on a progressive spatial encoding of MR images. Central in the development of these new experiments is the spatiotemporal manipulation of the spin interactions, a concept that originated from a search for methods capable of del...

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“…For 2D imaging, a class of pTx pulses called “spokes” has shown promising homogenization capability at both 7T 18 and 9.4T 19, 20. Spokes pulses typically consist of slice‐selective RF pulses, such as sinc or Shinnar‐Le Roux pulses 21, which are fully adjustable in both phase and amplitude per transmit channel, played out once or multiple times with interleave gradient blips between the subpulses to provide an effective spatial variation in phase as an extra degree of freedom. Static RF shim can be considered as the special case of one spoke.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution gradient‐recalled echo imaging at 9.4T using 16‐channel parallel transmit simultaneous multislice spokes excitations with slice‐by‐slice flip angle homogenization

Tse

Wiggins²,

Poser

2016

Magnetic Resonance in Med

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PurposeIn order to fully benefit from the improved signal‐to‐noise and contrast‐to‐noise ratios at 9.4T, the challenges of normalB1+ inhomogeneity and the long acquisition time of high‐resolution 2D gradient‐recalled echo (GRE) imaging were addressed.Theory and MethodsFlip angle homogenized excitations were achieved by parallel transmission (pTx) of 3‐spoke pulses, designed by magnitude least‐squares optimization in a slice‐by‐slice fashion; the acquisition time reduction was achieved by simultaneous multislice (SMS) pulses. The slice‐specific spokes complex radiofrequency scaling factors were applied to sinc waveforms on a per‐channel basis and combined with the other pulses in an SMS slice group to form the final SMS‐pTX pulse. Optimal spokes locations were derived from simulations.ResultsFlip angle maps from presaturation TurboFLASH showed improvement of flip angle homogenization with 3‐spoke pulses over CP‐mode excitation (normalized root‐mean‐square error [NRMSE] 0.357) as well as comparable excitation homogeneity across the single‐band (NRMSE 0.119), SMS‐2 (NRMSE 0.137), and SMS‐3 (NRMSE 0.132) 3‐spoke pulses. The application of the 3‐spoke SMS‐3 pulses in a 48‐slice GRE protocol, which has an in‐plane resolution of 0.28 × 0.28 mm, resulted in a 50% reduction of scan duration (total acquisition time 6:52 min including reference scans).ConclusionTime‐efficient flip angle homogenized high‐resolution GRE imaging at 9.4T was accomplished by using slice‐specific SMS‐pTx spokes excitations. Magn Reson Med 78:1050–1058, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

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Parameter relations for the Shinnar-Le Roux selective excitation pulse design algorithm (NMR imaging)

Cited by 731 publications

References 10 publications

Assessment of pulmonary perfusion in a single shot using SEEPAGE

Assessment of pulmonary perfusion in a single shot using SEEPAGE

Super‐resolved spatially encoded single‐scan 2D MRI

High‐resolution gradient‐recalled echo imaging at 9.4T using 16‐channel parallel transmit simultaneous multislice spokes excitations with slice‐by‐slice flip angle homogenization

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