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Pre-polarized MRI in a zero readout ...

Agrawal, Aarati.

Pre-polarized MRI in a zero readout magnetic field and radiofrequency selective excitation in zero-field NMR.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Pre-polarized MRI in a zero readout magnetic field and radiofrequency selective excitation in zero-field NMR.
作者:	Agrawal, Aarati.
面頁冊數:	59 p.
附註:	Chair: Alexander Pines.
附註:	Source: Dissertation Abstracts International, Volume: 65-09, Section: B, page: 4587.
Contained By:	Dissertation Abstracts International65-09B.
標題:	Engineering, Electronics and Electrical.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3146774
ISBN:	0496056735

Pre-polarized MRI in a zero readout magnetic field and radiofrequency selective excitation in zero-field NMR.
Agrawal, Aarati.

Pre-polarized MRI in a zero readout magnetic field and radiofrequency selective excitation in zero-field NMR. - 59 p.

Chair: Alexander Pines.

Thesis (Ph.D.)--University of California, Berkeley, 2004.

Pre-polarized MRI in a zero readout magnetic field would be advantageous for a number of reasons, mainly because of the elimination of magnetic field inhomogeneity and the effects of magnetic susceptibility gradients produced by the applied magnetic field. Here, I propose a pulse sequence and image reconstruction methodology that takes fully into account the concomitant components of the gradient magnetic field that would necessarily play a role in pre-polarized MRI in a zero readout magnetic field, and that are usually neglected in conventional MRI. The approach presented here applies not only to PMRI in a zero readout field but any MRI experiment where the gradient is on the same order of magnitude or greater than the constant applied magnetic field. For example, in high-resolution MRI, very large gradients are applied to obtain resolutions that are usually on the order of micrometers. Because of the large magnetic field gradients that are applied, high-resolution MRI performed at low-magnetic fields would result in large concomitant components of the gradient. Whether the applied readout magnet is very small or zero or whether very high-strength gradient magnetic fields are applied, a new approach to MRI is required that fully accounts for the concomitant components of the gradient magnetic field.

ISBN: 0496056735Subjects--Topical Terms:

226981
Engineering, Electronics and Electrical.

Pre-polarized MRI in a zero readout magnetic field and radiofrequency selective excitation in zero-field NMR.
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500 $a Chair: Alexander Pines.
500 $a Source: Dissertation Abstracts International, Volume: 65-09, Section: B, page: 4587.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2004.
520 # $a Pre-polarized MRI in a zero readout magnetic field would be advantageous for a number of reasons, mainly because of the elimination of magnetic field inhomogeneity and the effects of magnetic susceptibility gradients produced by the applied magnetic field. Here, I propose a pulse sequence and image reconstruction methodology that takes fully into account the concomitant components of the gradient magnetic field that would necessarily play a role in pre-polarized MRI in a zero readout magnetic field, and that are usually neglected in conventional MRI. The approach presented here applies not only to PMRI in a zero readout field but any MRI experiment where the gradient is on the same order of magnitude or greater than the constant applied magnetic field. For example, in high-resolution MRI, very large gradients are applied to obtain resolutions that are usually on the order of micrometers. Because of the large magnetic field gradients that are applied, high-resolution MRI performed at low-magnetic fields would result in large concomitant components of the gradient. Whether the applied readout magnet is very small or zero or whether very high-strength gradient magnetic fields are applied, a new approach to MRI is required that fully accounts for the concomitant components of the gradient magnetic field.
520 # $a Zero-field NMR was developed to overcome the instrinsic broadening of the resonance line in high-fields due to the dependence of interactions such as dipolar coupling on the orientation of the molecule with respect to the applied magnetic field in high-field, solid-state NMR. One major limitation, however, of zero-field NMR is the inability, so far, to selectively excite spins based on the frequency of the spins in the zero-field NMR spectrum. Selective excitation is important to selectively excite and detect NMR spectra from selected spins in order to simplify complex zero-field spectra which can result from just a few coupled spins in zero-field NMR. Selective excitation of spins is also applied to selective decoupling using multiple-pulse sequences or continuous-wave radiofrequency irradiation. Here, I suggest a method for radiofrequency selective excitation of the spins based on the NMR frequency of the spins in the zero-field spectrum. I derive the resonance conditions for radiofrequency selective excitation in a purely J-coupled and purely dipolar coupled spin system and show simulations of the effect of selective excitation using the applied radiofrequency field. The applied rf-pulse selectively rotates spin pairs based on the J-coupling or dipolar coupling frequency of the spins in purely coupled spin systems.
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