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The cardiac single photon emission computed tomography (SPECT) is an important research topic because of the large clinical demand and the need for improving image quality. It usually suffers from low count sensitivity and poor spatial resolution due to patient radiation safety concerns. In this study, hybrid cardiac imaging integrating elliptical orbit SPECT (E-SPECT) with computed tomography (CT) is proposed to better obtain the anatomical and physiological information of the cardiac and vascular systems. The geometric structure of this proposed hybrid imaging system is similar to that of an ellipse, containing multiple detectors with slit-slat collimation. The hybrid imaging system utilizes the elliptical geometry and multi-detectors to improve the sensitivity and signal to noise ratio (SNR), and incorporates a CT scanner into the system to obtain an accurate attenuation mapping matrix of the patient for image reconstruction. The iterative reconstruction algorithm with some constraints is used to reconstruct images. The constraint-based body contour is introduced to deal with severely truncated data from E-SPECT. The feasibility and advantage of the system is validated by simulations. Simulation results show that it is optimal for system design and the quality of reconstructed images are greatly improved. With an optimal sampling coverage angle between 210 • and 240 • , the hybrid cardiac imaging system proposed in the paper can achieves significant improvements in image spatial resolution, SNR and image fidelity. INDEX TERMS Attenuation correction (AC), computed tomography (CT), elliptical orbit, ordered subsets expectation maximization (OSEM), single photon emission computed tomography (SPECT), slit-slat collimation.