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FID sampling superior to spin‐echo sampling for T 2 * ‐based quantification of holmium‐loaded microspheres: Theory and experiment
Author(s) -
Seevinck Peter R.,
Seppenwoolde JanHenry,
Zwanenburg Jaco J.M.,
Nijsen Johannes F.W.,
Bakker Chris J.G.
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21785
Subject(s) - dephasing , sampling (signal processing) , free induction decay , spin echo , nuclear magnetic resonance , signal (programming language) , holmium , chemistry , diffusion , microsphere , detection limit , echo (communications protocol) , sampling time , magnetic resonance imaging , physics , analytical chemistry (journal) , biological system , mathematics , computer science , optics , chromatography , statistics , condensed matter physics , radiology , laser , computer network , detector , biology , programming language , thermodynamics , medicine , engineering , chemical engineering
This work demonstrates both theoretically and experimentally that multiple gradient‐echo sampling of free induction decay (MGEFID) is superior to MGE sampling of spin echo (MGESE) for T 2 * ‐based quantification of holmium‐loaded microspheres (HoMS). An interleaved sampling strategy was applied in great detail to characterize the MR signal behavior of FID and SE signals of gels and perfused rabbit livers containing HoMS in great detail. Diffusion sensitivity was demonstrated for MGESE sampling, resulting in non‐exponential signal decay on both sides of the SE peak and in an underestimation of the HoMS concentration. Other than MGESE sampling, MGEFID sampling was demonstrated to be insensitive to diffusion, to exhibit exponential signal decay, and to allow accurate T 2 * ‐based quantification of HoMS. Furthermore, a fit procedure was proposed extending the upper limit of quantifiable R 2 *relaxation rates to at least 1500 sec –1 . With this post‐processing step incorporated, MGEFID was shown to correctly estimate the integral amount of inhomogeneously distributed HoMS in liver tissue, up to a clinically relevant limit. All experimental findings could be explained with the theory of nuclear magnetic resonance (NMR) signal behavior in magnetically inhomogeneous tissues. HoMS were shown to satisfy the static dephasing regime when investigated with MGEFID and to violate the static dephasing conditions for MGESE at longer echo times typically used in SE. Magn Reson Med 60:1466–1476, 2008. © 2008 Wiley‐Liss, Inc.