Improved spatial-temporal reconstruction for cardiac and respiratory gated SPECT

Myocardial perfusion single photon emission computed tomography (SPECT) is an important imaging technique for evaluating coronary artery disease. It can provide information of both myocardial perfusion and ventricular function. However, SPECT images suffer from both cardiac and respiratory motion blur. In order to reduce the motion degrading, cardiac and respiratory gated SPECT imaging is used. In gated SPECT imaging, due to the lowered counts, the gated images will be more noisy than the ungated ones. Spatiotemporal (4D) processing is often used to reduce the noise level in gated images. In this thesis, we aim to investigate spatial and temporal processing techniques for improving the quality in cardiac and respiratory gated SPECT imaging.;First, we will investigate a piecewise spatial smoothing prior based on total-variation (TV) in 4D cardiac SPECT image reconstruction. Our goal is to explore whether a piecewise spatial smoothing prior will improve the image accuracy while reducing the noise. Motion-compensated temporal smoothing is known to play a key role in 4D cardiac gated SPECT reconstruction. Next, we will investigate whether better motion estimation could further improve the accuracy of reconstructed images. Respiratory motion is known to cause motion blur in SPECT image reconstruction, and respiratory gated SPECT imaging can be effective to combat its effect. We will develop reconstruction techniques in respiratory gated SPECT. Due to irregular respiratory motion, the data acquisition in each respiratory gate is not uniformly distributed among the acquisition angles, which would lead to limited-angle artifacts. To correct such artifacts, we propose an angle compensation method in the reconstruction. In order to deal with both cardiac and respiratory motion, we will investigate a 4D reconstruction approach for dual cardiac-respiratory gated SPECT reconstruction. Due to the radiation risk of myocardial perfusion imaging (MPI) scans, there is an urgent need to lower the radiation dose used in SPECT. We would explore the potential of using 4D reconstruction for lowering the dose in dual cardiac-respiratory gated SPECT.