Fig. 7. Magnetic resonance volumetric ventricular imaging after collagenase-induced hemorrhage. A , Representative 3D volume measurements of the ventricular systems at 2 and 24 h postcollagenase injection in mice randomized to 30% Xe or 0% Xe treatment. Fused 3D renderings of brain and ventricles revealed hydrocephalus predominantly involving the lateral ventricles, with relative sparing of the third and fourth ventricles, suggesting a noncommunicating pattern of volume increase. No etiology of aqueductal obstruction, however, was observed on the magnetic resonance images obtained. B , Hydrocephalus was greater in animals receiving 0% Xe. Horizontal bars indicate group mean values. Ventricular volumes for individual mice (open and closed circles ) were not different between groups at 2 h (P = 0.6). At 24 h, ventricular volumes were greater in the 0% Xe versus 30% Xe treatment groups (P = 0.02). Xe = Xenon.