We have already reported that after an injection for euthanasia, the signal intensity of optical coherence tomography (OCT) images are 2.7 times increased before cardiac arrest (CA) using OCT and rat brains without temperature control to show the potential of OCT to monitor tissue viability in brains [Appl. Opt.48, 4354 (2009)APOPAI0003-693510.1364/AO.48.004354]. In this paper, we similarly measured maintaining the primary temperature of rat brains. It was confirmed that when maintaining the primary temperature, the time courses of the ratios of signal intensity (RSIs) were almost the same as those without temperature control. RSIs after CA varied from 1.6 to 4.5 and depended on positions measured in tissues. These results mean that the OCT technique has clinical potential for applications to monitor or diagnose a focal degraded area, such as cerebral infarctions due to focal ischemia in brains.