Figure 1.

(a) Schematic diagram of 511 keV photons incident at an angle θ on a one-to-one coupled detector without any lightguide. (b) Schematic of a 511 keV photon interacting in two crystals first depositing 200 keV and then 311 keV. The three positioning algorithms define the 511 keV photon incident position as the red shaded crystal (Anger), blue shaded crystal (1^st max crystal), and grey shaded crystal (2^nd max crystal). The positioning error as calculated for the 1^st max crystal positioning algorithm is indicated.