Advances in 4D Gated Cardiac PET Imaging for Image Quality Improvement and Cardiac Motion and Contractility Estimation

Quantitative four-dimensional (4D) image reconstruction methods with respiratory and cardiac motion compensation are an active area of research in ECT imaging, including SPECT and PET. They are the extensions of three-dimensional (3D) statistical image reconstruction methods with iterative algorithms that incorporate accurate models of the imaging process and provide significant improvement in the quality and quantitative accuracy of the reconstructed images as compared to that obtained from conventional analytical image reconstruction methods. The new 4D image reconstruction methods incorporate additional models of the respiratory and cardiac motion of the patient to reduce image blurring due to respiratory motion and image noise of the cardiac-gated frames of the 4D cardiac-gated images. We describe respiratory motion estimation and gating method based on patient PET list-mode data. The estimated respiratory motion is applied to the respiratory gated data to reduce respiratory motion blur. The gated cardiac images derived from the list-model data are used to estimate cardiac motion. They are then used in the cardiac-gated images summing the motion-transformed cardiac-gated images for significant reduction in the gated images noise. Dual respiratory and cardiac motion compensation is achieved by combining the respiratory and cardiac motion compensation steps. The results are further significant improvements of the 4D gated cardiac PET images. The much improved gated cardiac PET image quality increases the visibility of anatomical details of the heart, which can be explored to provide more accurate estimation of the cardiac motion vector field and cardiac contractility.