Iterative EM reconstruction of cardiac small animal PET images using system point spread function modelling and MAP with anatomical priors

The goal of this work was to improve the image quality of small animal PET images by introducing in the reconstruction process the true system point spread function (PSF) and an anatomical image prior (MAP). The algorithm was tested on a mouse heart digital phantom (myocardium and ventricles) and on real acquired images of the Derenzo phantom and of a real mouse. For both the acquisitions two radiotracers were used, 18-FDG and 68Ga-chloride. A comparison between standard EM reconstruction and EM with PSF modelling and anatomical prior was performed. The system PSF was assumed to be a Gaussian function and its Full Width Half Maximum (FWHM) was modelled to be spatially variant in order to simulate the different spatial resolution inside the scanner field of view. A visual comparison of the images reconstructed with the standard EM and with the proposed image reconstruction method showed that the reconstructed images look much sharper and are very close to the true ones when using EM with PSF modelling and anatomical prior.