Simultaneous attenuation and scatter corrections from the projections in small animal PET imaging

Attenuation and scatter corrections are important in quantitative positron emission tomography (PET) imaging even in small animals such as mice and rats. In this work we describe a simple and efficient model to correct for both scatter and attenuation in a single operation. The model aims to solve the equation M = (A + F) P for the primaries P, corrected for attenuation and scatter, based on the measured coincidences M, the matrix of compensation for attenuation A and on the scatter fractions F issued from all emitting sources and contributing to M. The scatter functions are analytically calculated using Klein-Nishina formula, the scanner geometry and the detection efficiencies. This method was applied in measured data of line sources and hot spots phantoms as well as in rat heart and tumors and compared to Monte Carlo based simulations and to the single scatter simulation model developed by Watson et al. The corrected data showed a quantitative contrast and signal to noise ratio enhancement with respect to the uncorrected data. In terms of results, our method is comparable to that of Watson et al. The Monte Carlo simulations, where the primaries and the scattered events were separately registered, confirmed the accuracy of the new approach.