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On- and off-resonance T1ρ MRI in acute cerebral ischemia of the rat

✍ Scribed by Olli H.J. Gröhn; Heidi I. Mäkelä; Jouko A. Lukkarinen; Lance DelaBarre; Joseph Lin; Michael Garwood; Risto A. Kauppinen

Publisher
John Wiley and Sons
Year
2002
Tongue
English
Weight
688 KB
Volume
49
Category
Article
ISSN
0740-3194

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✦ Synopsis

Abstract

The ability of on‐resonance T~1ρ~ (T~1ρ~) and off‐resonance T~1ρ~ (T) measurements to indicate acute cerebral ischemia in a rat model of transient middle cerebral artery (MCA) occlusion was investigated at 4.7 T. T~1ρ~ was determined with B~1~ fields of 0.4, 0.8, and 1.6 G, and T with five offset frequencies (Δω) 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~1ρ~ and T acquired with Δo < 2.5 kHz showed positive contrast during the first hours of MCA occlusion in the ischemic tissue delineated by low diffusion. Interestingly, T contrast acquired with Δω > 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. Magn Reson Med 49:172–176, 2003. © 2003 Wiley‐Liss, Inc.

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