Fig. 10.

(Left) The 3-DOF RB translations estimated from the BM component of chest markers in subject 2 in Table I showing movement in X (of ~ 15 mm) with little Y or Z direction motion during SPECT imaging (first ~ 15 minutes). However, note that X, Y, and Z all change significantly at the time of transition from emission to transmission imaging when the camera heads move away from the patient and the transmission source is deployed. (Right) Again, the shift in lateral center-of-mass (x′com) of the heart from the trajectory followed as the camera rotates is shown. The shift in x′com computed using the segmented heart pixels from SPECT 2D projections (gray line) in the same subject agrees with that computed using external markers (black dotted line) as shown. There is a clear displacement of the xcom curve around 7 minutes, which matches the time of the sudden displacement in the X curve in the figure on the left. Also, there is a maximum displacement of about 3.4 pixels in the heart location as computed from the SPECT 2D projections around 8 minute, which is close to the displacement in X direction of about 16 mm.