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Rapid T 2 * mapping using interleaved echo planar imaging
Author(s) -
Howseman Alistair M.,
Thomas David L.,
Pell Gaby S.,
Williams Stephen R.,
Ordidge Roger J.
Publication year - 1999
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/(sici)1522-2594(199902)41:2<368::aid-mrm22>3.0.co;2-1
Subject(s) - echo planar imaging , imaging phantom , gradient echo , nuclear magnetic resonance , magnetic resonance imaging , distortion (music) , spin echo , pulse sequence , echo (communications protocol) , signal (programming language) , cerebral blood flow , nuclear medicine , computer science , physics , medicine , radiology , amplifier , computer network , cardiology , bandwidth (computing) , programming language
Magnetic resonance imaging methods that are sensitive to T 2 * are widely used in the study of blood oxygenation changes, most notably in functional studies of the brain. In these studies the signal intensity change in T 2 *‐weighted imaging is related to the coupling of cerebral blood flow and metabolism. Rapid measurement of T 2 * itself would offer a valuable method to quantify blood oxygenation changes indirectly and monitor their time course. An interleaved echoplanar imaging (EPI) sequence is presented here that allows maps of T 2 * to be generated in a few seconds. The sequence benefits from reduced geometric distortion and an improved point spread function compared with single‐shot EPI. A comparison among a set of T 2 *‐weighted interleaved EPI images, single‐shot EPI, and conventional gradient‐echo and spin‐echo methods is made using a compartmentalized doped water phantom. The interleaved sequence yields accurate T 2 * values when compared with reference measurements made using the slower gradient‐echo technique. Data acquired from the rat brain at 2.35 T prior to and during an anoxic challenge show, with high temporal resolution, the reduction in T 2 * associated with increased levels of deoxyhemoglobin. Magn Reson Med 41:368–374, 1999. © 1999 Wiley‐Liss, Inc.