Motion-compensated post-processing of gated cardiac SPECT images using a deformable mesh model

We present a post-reconstruction motion-compensated spatio-temporal filtering method for noise reduction in cardiac gated SPECT images. SPECT imaging suffers from low photon count due to radioactive dose limitations resulting in a high noise level in the reconstructed images. This is especially true in gated cardiac SPECT where the total number of counts is divided into a number of gates (time frames). Classical spatio-temporal filtering approaches, used in gated cardiac SPECT for noise reduction, do not accurately account for myocardium motion and brightening and therefore perform sub-optimally. The proposed post-reconstruction method consists of two steps: motion and brightening estimation and spatio-temporal motion-compensated filtering. In the first step we utilize a left ventricle model and a deformable mesh structure. The second step, which consists of motion-compensated spatio-temporal filtering, makes use of estimated myocardial motion to enable accurate smoothing. Additionally, the algorithm preserves myocardial brightening, a result of partial volume effect which is widely used as a diagnostic feature. The proposed method is evaluated quantitatively to assess noise reduction and the influence on estimated ejection fraction.