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Changes in the proton T 2 relaxation times of cerebral water and metabolites during forebrain ischemia in rat at 9.4 T
Author(s) -
Lei Hao,
Zhang Yi,
Zhu XiaoHong,
Chen Wei
Publication year - 2003
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.10490
Subject(s) - ischemia , forebrain , nuclear magnetic resonance , relaxation (psychology) , proton , chemistry , neuroscience , medicine , cardiology , physics , biology , central nervous system , nuclear physics
Abstract Proton T 2 relaxation times of cerebral water and metabolites were measured before, during, and after transient forebrain ischemia in rat at 9.4 T using localized proton magnetic resonance spectroscopy ( 1 H‐MRS) with Hahn echoes formed at different echo times (TEs). It was found that the T 2 values of water and N‐acetyl aspartate (NAA) methyl, but not total creatine (tCr) methyl, decrease significantly (∼10%) during ischemia, and this T 2 reduction is reversed by reperfusion. The T 2 reduction observed for NAA was most likely caused by the extravascular component of the blood oxygenation level‐dependent (BOLD) effect induced by a drastically increased deoxyhemoglobin content during ischemia. The absence of T 2 changes for tCr can probably be explained by the fact that the BOLD‐related T 2 decrease was counterbalanced by the conversion of phosphocreatine (PCr) to creatine (Cr), which has a longer T 2 than PCr, during ischemia. The changes in T 2 should be taken into account for the quantification of metabolite concentrations during ischemia. Magn Reson Med 49:979–984, 2003. © 2003 Wiley‐Liss, Inc.