Fig. 6.
Frequency content in the projection data acquired during in vivo mechanical ventilation of a pig, using either conventional mechanical ventilation (a), high-frequency oscillatory ventilation (b,c), or multi-frequency oscillatory ventilation (d). Frequency on the horizontal axis obtained from discrete Fourier transform using the scanner rotation frequency frot = 4 Hz as the sampling frequency. Thus subject motion frequencies greater than 0.5 frot are aliased. Spectral peaks correspond to either ventilatory motion or cardiogenic motion. Spectral peaks corresponding to heart rate are indicated by asterisks.