Comparison of statistical reconstructions with isotropic and anisotropic resolution

Statistical reconstruction methods based on the penalized maximum likelihood (or maximum a posteriori) principle have gained increasing attention in emission tomography. Fessler and Rogers have shown that the penalized maximum likelihood reconstruction with a conventional quadratic penalty results in anisotropic point spread functions (PSFs). Several approaches have been developed to design modified penalty functions to achieve isotropic PSFs. While an image with an isotropic PSF may be useful in some situations, its performance on clinical detection and quantitation tasks is unknown. In this paper, we compare the task performances using computer simulations. The lesion detectability is measured by a channelized Hotelling observer. The quantitation is evaluated by the bias and variance. The results show that reconstructions with an isotropic PSF may not be suitable for lesion detection and quantitation.