Effects of upward creep and respiratory motion in myocardial SPECT

In this study, the authors investigate the effects of two patient involuntary motions, namely upward creep (UC) and respiratory (RSP) motion, in myocardial SPECT images. A new realistic torso phantom was developed based on data from the Visual Human Project and using non-uniform rational B-splines (NURBS) modeling. The heart and diaphragm of the phantom move with a linear upward translation to model UC and move in a sinusoidal up and down fashion to model RSP motion. Simulated emission and transmission CT data sets were generated from the phantom using a L-shaped dual-camera SPECT system with a radioactivity distribution modeling that of a Tl-210 study with UC of 2 cm. The effects of attenuation and collimator-detector response are included in the simulation. A patient study with the same extent of UC was used for comparison. Both simulated and patient data were reconstructed with and without correction for attenuation and UC. Similar data sets were generated from the phantom with RSP motion. The simulated reconstructed images demonstrated distinct UC and RSP artifacts in the inferior region of the myocardium. The UC artifact can be greatly reduced with simple UC correction. However, the correction of RSP artifact may require respiratory gating.