The effect of heart motion on kinetic parameter estimates for dynamic cardiac SPECT

Dynamic cardiac SPECT is used to estimate kinetic rate parameters that describe the washin and washout of tracer activity between the blood and the myocardial tissue. These kinetic parameters correlate to myocardial perfusion. There are, however, many physical aspects associated with dynamic SPECT which introduce bias and variance into the estimates. This paper describes a study which investigates the effect of heart motion on kinetic parameter estimates. Dynamic SPECT simulations are performed using a beating version of the MCAT phantom. The amount of blood and background activity in the myocardial tissue regions of interest is shown to vary over the cardiac cycle causing errors in the kinetic parameter estimates, particularly estimates of the washin rate constant. The effect of cardiac motion on kinetic parameter estimates is reduced by bias and variance introduced by photon noise and geometric collimator response. This suggests that techniques used to correct for motion must do so without further reducing photon statistics