The longitudinal magnetization of hyperpolarized media, such as hyperpolarized 129Xe, 3He, etc., is nonrenewable. When the MRI data acquisition begins at the k-domain center, a constant flip angle (CFA) results in an image of high signal-to-noise ratio (SNR) but sacrifices the accuracy of spatial information. On the other hand, a variable flip angle (VFA) strategy results in high accuracy but suffers from a low SNR. In this paper, we propose a novel scheme to optimize both the SNR and accuracy, called constant-variable flip angles (CVFA). The proposed scheme suggests that hyperpolarized magnetic resonance signals are firstly acquired through a train of n* CFA excitation pulses, followed by a train of N–n* VFA excitation pulses. We simulate and optimize the flip angle used in the CFA section, the number of CFA excitation pulses, the number of VFA excitation pulses, and the initial and final variable flip angles adopted in the VFA section. Phantom and in vivo experiments demonstrate the good performance of the CVFA designs and their ability to maintain both high SNR and spatial resolution.
A fast and simple method for calibrating the flip angle in hyperpolarized 13C MRS experiments
From The DNP-NMR Blog:
A fast and simple method for calibrating the flip angle in hyperpolarized 13C MRS experiments
Giovannetti, G., et al., A fast and simple method for calibrating the flip angle in hyperpolarized 13C MRS experiments. Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering, 2015: p. n/a-n/a.
http://dx.doi.org/10.1002/cmr.b.21282
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News from NMR blogs
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07-14-2015 02:59 AM
Apparent rate constant mapping using hyperpolarized [1–13C]pyruvate
From The DNP-NMR Blog:
Apparent rate constant mapping using hyperpolarized pyruvate
Khegai, O., et al., Apparent rate constant mapping using hyperpolarized pyruvate. NMR in Biomedicine, 2014. 27(10): p. 1256-1265.
http://dx.doi.org/10.1002/nbm.3174
Optimal variable flip angle schemes for dynamic acquisition of exchanging hyperpolarized substrates
From The DNP-NMR Blog:
Optimal variable flip angle schemes for dynamic acquisition of exchanging hyperpolarized substrates
Xing, Y., et al., Optimal variable flip angle schemes for dynamic acquisition of exchanging hyperpolarized substrates. J. Magn. Reson., 2013. 234(0): p. 75-81.
http://dx.doi.org/10.1016/j.jmr.2013.06.003
nmrlearner
News from NMR blogs
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11-21-2013 01:14 AM
[Stan NMR blog] Gravitoid constant is now part of OEIS (A208745)
Gravitoid constant is now part of OEIS (A208745)
The gravity engineering article where it was defined has been updated.
Source: Stan blog library
[Question from NMRWiki Q&A forum] How can I calculate a carbon-proton coupling constant for a molecule?
How can I calculate a carbon-proton coupling constant for a molecule?
I'm trying to explain a missing HMBC peak, and having a coupling constant less than 10 Hz would do that nicely. It's a formamidine derivative with a 3 bond correlation N=CHNC The C is a quaternary carbon in a benzene ring. Any help would be appreciated.
Check if somebody has answered this question on NMRWiki QA forum
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News from other NMR forums
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02-04-2011 07:12 PM
[NMR paper] Constant-time multidimensional electrophoretic NMR.
Constant-time multidimensional electrophoretic NMR.
Related Articles Constant-time multidimensional electrophoretic NMR.
J Magn Reson. 2002 Jun;156(2):181-6
Authors: Li E, He Q
Multidimensional electrophoretic NMR (ENMR) has been introduced to determine structures of coexisting proteins and protein conformations in solution. Signals of different proteins are separated in a new dimension of electrophoretic flow according to their characteristic electrophoretic mobilities. The electrophoretic interferograms have been generated in the flow...
Constant-variable flip angles for hyperpolarized media MRI #DNPNMR
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