Physiological monitoring of small animals during magnetic resonance imaging

Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen saturation and end-tidal CO2 (ETCO2) of expired gas. All physiologic parameters were successfully monitored in Sprague-Dawley rats without interfering with EEG recordings during simultaneous fMRI and MRS studies. Body temperature, heart rate, blood pressure, blood oxygen saturation, and ETCO2, were maintained between 36.5 and 37.5 degrees C, 250-450 beats/min, 136+/-17 mmHg, >90%, and 20-35 mmHg, respectively for 6-8 h under inhalational anesthesia. This set-up could be extended to study in vivo applications in other laboratory animals with only minor modifications.