Development of a large-angle pinhole gamma camera with depth-of-interaction capability for small animal imaging

Abstract

A large-angle gamma camera was developed for imaging small animal models used in medical and biological research. The simulation study shows that a large field of view (FOV) system provides higher sensitivity with respect to a typical pinhole gamma cameras by reducing the distance between the pinhole and the object. However, this gamma camera suffers from the degradation of the spatial resolution at the periphery region due to parallax error by obliquely incident photons. We propose a new method to measure the depth of interaction (DOI) using three layers of monolithic scintillators to reduce the parallax error. The detector module consists of three layers of monolithic CsI(Tl) crystals with dimensions of 50.0×50.0×2.0 mm 3 , a Hamamatsu H8500 PSPMT and a large-angle pinhole collimator with an acceptance angle of 120 • . The 3-dimensional event positions were determined by the maximum-likelihood position-estimation (MLPE) algorithm and the pre-generated look up table (LUT). The spatial resolution (FWHM) of a Co-57 point-like source was measured at different source position with the conventional method (Anger logic) and with DOI information. We proved that high sensitivity can be achieved without degradation of spatial resolution using a large-angle pinhole gamma camera: this system can be used as a small animal imaging tool. KEYWORDS: Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA); Image reconstruction in medical imaging; Front-end electronics for detector readout; Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc)