Multimodality rodent imaging chambers for use under barrier conditions with gas anesthesia.

PURPOSE: The ability to reproducibly and repeatedly image rodents in noninvasive imaging systems, such as small-animal positron emission tomography (PET) and computed tomography (CT), requires a reliable method for anesthetizing, positioning, and heating animals in a simple reproducible manner. In this paper, we demonstrate that mice and rats can be reproducibly and repeatedly imaged using an imaging chamber designed to be rigidly mounted on multiple imaging systems. PROCEDURES: Mouse and rat imaging chambers were made of acrylic plastic and aluminum. MicroCT scans were used to evaluate the positioning reproducibility of the chambers in multimodality and longitudinal imaging studies. The ability of the chambers to maintain mouse and rat body temperatures while anesthetized with gas anesthesia was also evaluated. RESULTS: Both the mouse and rat imaging chambers were able to reproducibly position the animals in the imaging systems with a small degree of error. Placement of the mouse in the mouse imaging chamber resulted in a mean distance of 0.23 mm per reference point in multimodality studies, whereas for longitudinal studies the mean difference was 1.11 mm. The rat chamber resulted in a mean difference of 0.46 mm in multimodality studies and a mean difference of 4.31 mm in longitudinal studies per reference point. The chambers maintained rodent body temperatures at the set point temperature of 38 degrees C. CONCLUSIONS: The rodent imaging chambers were able to reproducibly position rodents in tomographs with a small degree of variability and were compatible with routine use. The embedded anesthetic line and heating system was capable of maintaining the rodent's temperature and anesthetic state, thereby enhancing rodent health and improving data collection reliability.

MicroCT liver contrast agent enhancement over time, dose, and mouse strain.

PURPOSE: The aim of this study was to examine strain differences in the uptake of Fenestra liver contrast agent (LC) in Nude, C57, and severe-combined immunodeficient (SCID) mice. In addition, we aimed to determine optimum dosing and to determine if there are positron emission tomography (PET)-attenuation effects on 2-deoxy-2[F-18]fluoro-D-glucose (FDG) values due to Fenestra LC. PROCEDURES: Nude, C57, and SCID mice were injected via tail vein at 5.0, 7.5, 10.0, and 15.0 ml/kg with contrast agent and imaged using micro computed tomography (microCT) 2 h after uptake and then daily up to 7 days. Mice were imaged by microPET/CT with FDG, with or without contrast agent. RESULTS: Significant variations in contrast were observed between mouse strains. SCID mice had significantly more spleen uptake of contrast than the other strains, and C57 mice had significantly more liver uptake of contrast than other strains. Across all strains, the spleen showed significantly higher uptake and duration of contrast than liver. Only the heart showed a significant attenuation of FDG uptake following contrast administration. CONCLUSIONS: Strain-specific variations in Fenestra LC uptake and signal duration were observed. At 7.5 ml/kg, this contrast agent is effective for imaging for 1 day, whereas at 15 ml/kg, it can be used up to 1 week. Fenestra LC does not appear to attenuate FDG uptake at 15 ml/kg for most tissues; therefore, it can be used in conjunction with microPET imaging studies.