Brain temperature measurements in rats: A comparison of microwave and ambient temperature exposures

Abstract

In an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or "hot spots," in the brain of these animals. In the first study, after a 30-min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time-temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2 degrees C. In this study, the 30-min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.

Spontaneous temperature changes in the 2-vessel occlusion model of cerebral ischemia in rats

“…Previous studies using non-ISC rats have shown a high degree of correlation between T b and T c in conscious rats Ward et al 1986), and the absolute difference between T b and T c , when measured with telemetry, is similar in non-ISC (DeBow and and ISC rats (present study). Although T c accurately predicts T b in normal and untreated ISC rats, actively heating an animal with an infrared lamp may overheat T b relative to T c (Plahta et al 2004).…”

Perspectives for Ag2S NIR-II nanoparticles in biomedicine: from imaging to multifunctionality

“…Variations in brain temperature are typically small (< 3°C) due to the presence of regulatory mechanisms based in the interplay between cerebral blood flow and cerebrospinal fluid circulation. [88][89][90][91][92][93] These mechanisms maintain brain temperature within a narrow range, making high thermal sensitivity an essential feature of any luminescent nanothermometers applied for recording brain temperature. Ag2S NPs, with their thermal sensitivity of up to 4 %/°C, allow recording sub-degree temperature changes.…”

Empirical validation of SAR values predicted by FDTD modeling*†

“…Various investigators [Chou et al, 1985;Ward et al, 1986, Walters et al, 1998] have previously examined the in¯uence of orientation relative to the EMF source on regional brain heating and therefore on localized SAR in rats. In these reports, data obtained using different experimental procedures and equipment were combined in order to ascertain orientation effects.…”