Figure 3

Heartbeat dynamics extracted from the time-lapse (4D) OAT data. (A) Image spectrum, obtained by summing the frequency spectra for all voxels within the FOV. The peak fundamental frequency at 3 Hz was assumed to be the heart rate. (B) Temporal profiles of OA signals from selected voxels sampled at 10 ms temporal resolution. The cardiac waveform was characterized by a voxel selected at the left ventricular wall, and the systole and diastole states are marked. Voxels selected at the pulmonary, mitral, and tricuspid valves are further shown. The semilunar valve was open during cardiac systole, in contrast to the two atrioventricular valves, which closed during systole and opened during diastole. The dotted lines indicate the transition between the open and close valves, consisting of four sampling events, and the cross-sectional close-up images (y - plane) of the respective valves corresponding to these time points are shown in (C). The corresponding locations of the image slices are indicated in Fig. 2B,C.