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Acute cerebral ischemia in rats studied by Carr‐Purcell spin‐echo magnetic resonance imaging: Assessment of blood oxygenation level‐dependent and tissue effects on the transverse relaxation
Author(s) -
Kavec Martin,
Gröhn Olli H.J.,
Kettunen Mikko I.,
Silvennoinen M. Johanna,
Garwood Michael,
Kauppinen Risto A.
Publication year - 2004
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.20089
Subject(s) - ischemia , parenchyma , magnetic resonance imaging , relaxation (psychology) , brain tissue , nuclear magnetic resonance , oxygenation , medicine , brain ischemia , pathology , anesthesia , anatomy , physics , radiology
Abstract Acute cerebral ischemia has been shown to be associated with an enhanced transverse relaxation rate in rat brain parenchyma, chiefly due to the blood oxygenation level‐dependent (BOLD) effect. In this study, Carr‐Purcell R 2 (CP R 2 ), acquired both with short and long time intervals between centers of adiabatic π‐pulses (τ CP ), was used to assess the contributions of BOLD and tissue effects to the transverse relaxation in two brain ischemia models of rat at 4.7 T. R 1ρ and diffusion MR images were also acquired in the same animals. During the first minutes of global ischemia, the long τ CP R 2 in brain parenchyma increased, whereas the short τ CP R 2 was unchanged. Based on the simulations, and using constraints of intravascular BOLD effect on parenchymal R 2 , the former observation was ascribed to be due to susceptibility changes arising in the extravascular compartment. R 1ρ declined almost immediately after the onset of focal cerebral ischemia, and further declined during the evolution of ischemic damage. Interestingly, short τ CP CP R 2 started to decline after some 20 min of focal ischemia and declined over a time course similar to that of R 1ρ , indicating that it may be an MRI marker for irreversible tissue changes in cerebral ischemia. The present results show that CP R 2 MRI can reveal both tissue‐ and blood‐derived contrast changes in acute cerebral ischemia. Magn Reson Med 51:1138–1146, 2004. © 2004 Wiley‐Liss, Inc.