Effects of upward creep and respiratory motion in myocardial SPECT

In this study, we investigate the effects of two patient involuntary motion s, namely upward creep (UC) and respiratory (RSP) motion, in myocardial SPE CT images. A new realistic torso phantom was developed based on data from t he Visual Human Project and using non-uniform rational B-splines (NURBS) mo deling. The heart and diaphragm of the phantom move with a linear upward tr anslation to model UC and move in a sinusoidal up and down fashion to model RSP motion. Simulated emission and transmission CT data sets were generate d from the phantom using a G-shaped dual-camera SPECT system with a radioac tivity distribution modeling that of a Tl-210 study with UC of 2 cm. The ef fects of attenuation and collimator-detector response are included in the s imulation. A patient study with the same extent of UC was used for comparis on. Both simulated and patient data were reconstructed with and without cor rection for attenuation and UC. Similar data sets were generated from the p hantom with RSP motion. The simulated reconstructed images demonstrated dis tinct UC and RSP artifacts in the inferior region of the myocardium. The UC artifact can be greatly reduced with simple UC correction. However, the co rrection of RSP artifact may require respiratory gating.