Comparison of CT (A) and FDG-PET (B) images of the sedated mouse without positive-pressure ventilation. The transverse images were obtained with isoflurane anesthesia using a nose cone (‘spontaneous’ ventilation) (A, B). The absence of ventilation resulted in pulmonary congestion (A, arrow) and presumed increase in PET image noise and errors in tracer uptake (B). (C) Comparison of CT scans obtained with spontaneous ventilation and after orotracheal intubation and positive-pressure ventilation (‘positive-pressure’ ventilation) demonstrated a significant difference in lung volumes (t test, p <. 001, asterisk) (N = 3). (D) Comparison of FDG-PET scans obtained with spontaneous ventilation and positive-pressure ventilation (‘positive-pressure’ ventilation) demonstrated a trend toward lower baseline SUV levels with positive-pressure ventilation.