Effects of in-pulse transverse relaxation in 3D ultrashort echo time sequences: analytical derivation, comparison to numerical simulation and experimental application at 3T

Journal of Magnetic Resonance
Fabian SpringerFritz Schick

Abstract

The introduction of ultrashort-echo-time-(UTE)-sequences to clinical whole-body MR scanners has opened up the field of MR characterization of materials or tissues with extremely fast signal decay. If the transverse relaxation time is in the range of the RF-pulse duration, approximation of the RF-pulse by an instantaneous rotation applied at the middle of the RF-pulse and immediately followed by free relaxation will lead to a distinctly underestimated echo signal. Thus, the regular Ernst equation is not adequate to correctly describe steady state signal under those conditions. The paper presents an analytically derived modified Ernst equation, which correctly describes in-pulse relaxation of transverse magnetization under typical conditions: The equation is valid for rectangular excitation pulses, usually applied in 3D UTE sequences. Longitudinal relaxation time of the specimen must be clearly longer than RF-pulse duration, which is fulfilled for tendons and bony structures as well as many solid materials. Under these conditions, the proposed modified Ernst equation enables adequate and relatively simple calculation of the magnetization of materials or tissues. Analytically derived data are compared to numerical results obtained...Continue Reading

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Citations

Aug 7, 2013·Journal of Magnetic Resonance·Dan Xiao, Bruce J Balcom
Sep 22, 2015·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Misung HanRoland Krug
Mar 15, 2016·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Ethan M JohnsonJohn M Pauly
Mar 25, 2011·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Gunther HelmsPeter Dechent
Dec 6, 2012·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Kevin M JohnsonScott Nagle
Feb 27, 2013·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Fabian SpringerFritz Schick
Sep 16, 2015·Scandinavian Journal of Medicine & Science in Sports·U GrosseF Springer
Dec 19, 2013·Journal of Magnetic Resonance Imaging : JMRI·Ulrich GrosseRoland Syha
Feb 18, 2014·Journal of Magnetic Resonance·Jonathan Mitchell
Jan 8, 2014·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·General LeungJim M Wild
Apr 16, 2019·NMR in Biomedicine·Khaoula Bouazizi, Geneviève Guillot
May 11, 2016·Journal of Magnetic Resonance Imaging : JMRI·Christiaan G OverduinTom W J Scheenen
Mar 25, 2019·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Xin LiCharles S Springer
Aug 27, 2015·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Michael CarlJiang Du
Nov 30, 2019·Progress in Nuclear Magnetic Resonance Spectroscopy·Markus Weiger, Klaas P Pruessmann

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