Scatter/trues detection efficiency compensation in scatter correction of PET emission data

In positron emission tomography (PET), a detector’s response to scattered radiation may be different from its response to unscattered (true coincidence) photons. This difference should be accounted for during normalization and scatter correction. We show that only a knowledge of the ratio of the scatter to trues efficiencies is necessary, however. We describe a new technique for measuring the scatter/trues detection efficiency ratio, and a procedure for applying this compensation during the scatter correction of PET emission data. We present some initial results, confirmed by simulations, indicating that the scatter/trues efficiencies may vary by up to 20% for a Siemens BrainPET MR insert in the vicinity of block gaps near the center of the transaxial field of view. These variations could result in ±5% variations in scatter corrected images if left uncompensated.