title: On- and off-resonance T(1rho) MRI in acute cerebral ischemia of the rat.
abstract: The ability of on-resonance T(1rho) (T(1rho)) and off-resonance T(1rho) (T(1rho)(off)) measurements to indicate acute cerebral ischemia in a rat model of transient middle cerebral artery (MCA) occlusion was investigated at 4.7 T. T(1rho) was determined with B(1) fields of 0.4, 0.8, and 1.6 G, and T(1rho)(off) with five offset frequencies ((Delta)omega) ranging from 0-7.5 kHz at B(1) of 0.4 G, yielding effective B(1) (B(eff)) from 0.4 to 1.8 G. Diffusion, T(1), and T(2) were also quantified. Both T(1rho) and T(1rho)(off) acquired with (Delta)(o)< 2.5 kHz showed positive contrast during the first hours of MCA occlusion in the ischemic tissue delineated by low diffusion. Interestingly, T(1rho)(off) contrast acquired with (Delta)omega > 2.5 kHz was clearly less sensitive to ischemic alterations, and developed with a delayed time course. This discrepancy is thought to be a consequence of the frequency dependency of cross-relaxation during irradiation with spin-lock pulses.
authors.affiliation: Department of Biomedical NMR, National Bio-NMR Facility, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
authors.forename: Olli H J
authors.initials: OH
authors.lastname: Gröhn
authors.forename: Heidi I
authors.initials: HI
authors.lastname: Mäkelä
authors.forename: Jouko A
authors.initials: JA
authors.lastname: Lukkarinen
authors.forename: Lance
authors.initials: L
authors.lastname: DelaBarre
authors.forename: Joseph
authors.initials: J
authors.lastname: Lin
authors.forename: Michael
authors.initials: M
authors.lastname: Garwood
authors.forename: Risto A
authors.initials: RA
authors.lastname: Kauppinen
mesh_terms: D000208:Acute Disease; D000818:Animals; D001921:Brain / Q000473:pathology*; D002545:Brain Ischemia / Q000175:diagnosis*; D003250:Constriction; D002546:Ischemic Attack, Transient / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D020768:Middle Cerebral Artery / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar