PURPOSE: To develop a method for body magnetic resonance imaging (MRI) of conscious mice and investigate the effect of isoflurane anesthesia and hypothermia on the hepatic kinetics of gadoxetate disodium (Gd-EOB-DTPA). MATERIALS AND METHODS: Conscious or anesthetized mice were restrained on a holder and the rectal temperature was measured serially. Serial MRI of the liver was performed after intravenous injection of Gd-EOB-DTPA with or without temperature control. Three mice were studied for each condition. RESULTS: The temperature dropped rapidly in anesthetized mice beside the MR unit. The decline was less prominent in conscious mice. The temperature decreased less in anesthetized mice and remained constant in conscious mice in the radiofrequency (RF) coil. The washout of Gd-EOB-DTPA was slower in anesthetized hypothermic mice than in conscious normothermic mice. Warmed anesthetized mice showed faster washout, and cooled conscious mice showed delayed washout. Severer hypothermia in anesthetized mice resulted in weaker initial enhancement and slower washout. CONCLUSION: By separately manipulating the presence or absence of anesthesia and hypothermia, we demonstrated that washout of Gd-EOB-DTPA was delayed under hypothermia, regardless of anesthesia. Serial body MRI of conscious mice was feasible and allowed the evaluation of kinetics of a contrast agent, while excluding the possible effects of anesthesia.
PURPOSE: To develop a method for body magnetic resonance imaging (MRI) of conscious mice and investigate the effect of isoflurane anesthesia and hypothermia on the hepatic kinetics of gadoxetate disodium (Gd-EOB-DTPA). MATERIALS AND METHODS: Conscious or anesthetized mice were restrained on a holder and the rectal temperature was measured serially. Serial MRI of the liver was performed after intravenous injection of Gd-EOB-DTPA with or without temperature control. Three mice were studied for each condition. RESULTS: The temperature dropped rapidly in anesthetized mice beside the MR unit. The decline was less prominent in conscious mice. The temperature decreased less in anesthetized mice and remained constant in conscious mice in the radiofrequency (RF) coil. The washout of Gd-EOB-DTPA was slower in anesthetized hypothermic mice than in conscious normothermic mice. Warmed anesthetized mice showed faster washout, and cooled conscious mice showed delayed washout. Severer hypothermia in anesthetized mice resulted in weaker initial enhancement and slower washout. CONCLUSION: By separately manipulating the presence or absence of anesthesia and hypothermia, we demonstrated that washout of Gd-EOB-DTPA was delayed under hypothermia, regardless of anesthesia. Serial body MRI of conscious mice was feasible and allowed the evaluation of kinetics of a contrast agent, while excluding the possible effects of anesthesia.