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Reducing voxel bleed in hadamard‐encoded MRI and MRS
Author(s) -
Goelman Gadi,
Liu Songtao,
Gonen Oded
Publication year - 2006
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.20903
Subject(s) - hadamard transform , voxel , pulse (music) , computer science , physics , point spread function , algorithm , nuclear magnetic resonance , encoding (memory) , optics , artificial intelligence , quantum mechanics , detector
The point spread function (PSF) of Hadamard encoding deviates from its ideal profile due to practical (as opposed to intrinsic) reasons. Finite radiofrequency (RF) pulse length and gradient strength cause slice profile imperfections that lead to cross‐talk (“voxel bleed”) as large as 17% for a 1‐KHz bandwidth, 5.12‐ms RF pulse under 3 mT/m. This could adversely affect localization and quantification, and consequently clinical usefulness. A simple modification of the Hadamard RF pulse synthesis that exploits its unique ability to encode noncontiguous slices is proposed and shown to markedly improve the PSF. Computer simulation, in vitro and in vivo experiments confirm the theoretical derivation of voxel bleed reduction from ∼17% to below 5% per Hadamard‐encoded direction. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.