Simultaneous attenuation and scatter corrections in small animal PET imaging.

The aim of this work is to simultaneously correct for attenuation and scatter in PET by analytically assessing the distribution of the scattered photons using the emission and the transmission images, the probability of scatter interactions and the detection efficiency. Above the usual lower energy threshold of 350 keV, the attenuated photons are dominantly those which have undergone a Compton scattering. By considering that each pixel in the image is the measurement of the transmitted photons through the subject, added to the contribution from the other sources by means of their scatter at this position, a simple equation is established accounting for the primaries by simultaneously correcting the data for attenuation and scatter for all emitting sources. This new method was applied in Monte Carlo simulated and measured data with the Sherbrooke small animal PET scanner in line sources, hot spot phantoms, and in rat hearts and tumors, and was compared to the approach developed by Watson et al.