Mi. Kettunen et al., Cerebral T-1 rho relaxation time increases immediately upon global ischemia in the rat independently of blood glucose and anoxic depolarization, MAGN RES M, 46(3), 2001, pp. 565-572
Citations number
40
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Time-dependent changes of T-1 in the rotating frame (T-1 rho), diffusion, T
-2, and magnetization transfer contrast on cardiac arrest-induced global is
chemia in rat were investigated. T-1 rho, a acquired with spin lock amplitu
des >0.6 G, started to increase 10-20 sec after cardiac arrest followed by
an increase within 3-4 min to a level that was 6-8% greater than in normal
brain. The ischemic T-1 rho response coincided with the drop of water diffu
sion coefficient in normoglycemic animals. However, unlike the rate of diff
usion, the kinetics of T-1 rho were not affected by either preischemic hypo
glycemia or hyperglycemia. Similar to diffusion, the kinetics of anoxic dep
olarization were dependent on preischemic blood glucose levels. Ischemia ca
used a reduction in the Hahn spin echo T-2 as a result of blood oxygenation
level-dependent (BOLD) effect; maximal negative BOLD seen by 40 sec. In th
e animals injected with an ironoxide particle contrast agent, AMI-227, prio
r to the insult, both T-1 rho and T-2 immediately increased in concert on i
nduction of ischemia. In contrast to the T-1 rho and diffusion changes, a m
uch slower change in magnetization transfer contrast was evident over the f
irst 20 min of ischemia. These data demonstrate that T-1 rho immediately in
creases following ischemia and that the pathophysiological mechanisms affec
ting this relaxation time may not directly involve magnetization transfer.
The mechanisms prolonging T-1 rho differ from those affecting water diffusi
on with respect to their sensitivities to glucose and are apparently indepe
ndent of membrane depolarization. (C) 2001 Wiley-Liss, Inc.