Accurate prediction of final lesion is critically important for clinical decision making in the management of acute ischemia stroke patients. In addition to the widely utilized perfusion and diffusion parameters, an MR derived cerebral oxygen metabolism index, which includes both cerebral blood flow (CBF) and oxygen consumption measurements using R2' (OMI_ R2'), may be a potential candidate for infarction prediction. In this study, we sought to evaluate how these MR parameters may delineate infarction in rats with ischemic injury. There is overwhelming evidence from animal studies showing that cooling may improve outcome after cerebral ischemia, while hyperthermia exacerbates neurological injury. However, how physiology parameters during ischemic injury are modulated by brain temperature is largely unknown. In this study, we first designed an MR compatible focal brain temperature manipulation system, which can regulate brain temperature, while keeping body temperature and other physiology parameters within the normal range. The relationship between T1 and temperature in brain tissue was investigated, which can be used to derive the brain temperature for the studies under hypothermic conditions. The relationship between CBF and temperature was also studied under ischemic condition. Our results showed that this device can manipulate brain temperature from 39 to the target temperature of 29 within 10 minutes and maintain it for a long period of time. Furthermore, the device allows flexible manipulation of brain temperature. A highly linear relationship between the change of T1 and change of temperature was observed. Highly linear relationships between CBF and temperature in regions with different severity of ischemic conditions were found, with the highest slope in the normal region, whiles the lowest slope in the infarct region. The possible explanation for this finding may be the breakdown of auto regulation of cerebral hemodynamic in ischemic regions. The GESSE sequence was utilized for the measurement of R2'. Multiple navigator echoes were used for motion correction. In addition, the z-shimming method was applied for B0 inhomogeneity correction. Highly consistent R2' measurements were obtained in normal rats, with a standard deviation less than 1.4Hz and 2.1Hz in subcortical and cortical areas, respectively. With 45 minutes of MCAO, the relationship between ADC, CBF, R2' and OMI_R2' right before reperfusion was studied. Elevated R2' in both the lesion and peri-lesion regions were observed. The elevated R2' in the peri-lesion region leads to a comparable OMI_R2' as that of the contralateral hemisphere, suggesting that tissue may remain viable. However, a similar behavior was also observed in the core area which will require additional investigation
