Quantification of inter-crystal scattering and parallax effect in pixelated high resolution small animal gamma camera: A Monte Carlo study

Abstract

Small animal SPECT imaging is currently a rapidly expanding field since high resolution in vivo measurements can readily be achieved. Since dedicated high resolution scanners employ smaller crystal array dimensions, deteriorative resolution factors are mainly caused by inter-crystal scatter (ICS) and parallax effect(also called penetration). The foremost goal of present study is to quantify both penetration and inter-crystal scatter effects as function of crystal material with various pixel sizes (0.5:0.5:3) and crystal length. To fulfill this aim, GATE simulation package was employed. Different scintillators including NaI, CsI and LaBr3 were exposed by 140KeV pencil beam in both perpendicular and oblique angles. When irradiation is perpendicular to detector array, percentage of events undergo ICS was most and least in pixel sizes 0.5 × 0.5 and 3 × 3 mm2 for crystal materials of LaBr3 and CsI, respectively. The results also revealed as the angle of non perpendicular incidence increases, detected events in central pixel were significantly dropped. According to results, GATE is useful tool for investigation of photon interaction in gamma camera detectors in order to precisely model the ICS and penetration behavior for incorporating these effects during image reconstruction for resolution recovery purposes. © 2011 Springer-Verlag.