Randoms correction for gamma camera based PET list-mode reconstruction

Gamma cameras used in PET mode are operating at high count rates, which leads to a high number of randoms in the acquired data. These data are often stored in listmode format to obtain more accurate reconstructions. We propose a randoms correction for an iterative list mode based reconstruction, which is based on the single photon distribution on each detector head. The method takes the spatial variation of the random coincidences into account. From the singles rates on each head the number of randoms in each voxel of the reconstruction is estimated. This is done by integrating the product of the singles over the solid angle formed by the voxel and both detectors. Camera rotation is taken Into account by integration this over all detector angles. This method only requires a quick singles scan prior or after the acquisition when there is unknown activity outside the FOV. When there is no activity outside the FOV or it is known the singles distribution on the detector head can be estimated from the reconstructed images. The randoms distribution can be subtracted after the reconstruction has been done