Investigation of the Intrinsic Spatial Resolution of an Intensified EMCCD Scintillation Camera

In this paper, we present an experimental and Monte Carlo investigation of the intrinsic spatial resolution that can be achieved with the intensified electron-multiplying charge-coupled device (I-EMCCD) gamma camera . This detector has a very low readout noise, an ultra-high spatial resolution and a large active area of ~ 80 mm diameter, which is well-suited for small animal imaging applications. The intrinsic detector resolutions achieved with different scintillators and under different experimental conditions were compared. In this study, the simple centroiding method was compared with two model-fitting approaches for finding the locations of gamma ray interactions. The results from Monte Carlo simulation have demonstrated that with an appropriate detector configuration, it is possible to achieve an intrinsic resolution of ~ 30 mum FWHM for detecting 27-35 keV gamma rays. The I-EMCCD scintillation camera offers a promising candidate for future ultra-high resolution SPECT imaging applications.

I. Introduction

In recent years, substantial efforts have been made to improve the imaging resolution of SPECT systems dedicated to small lab studies. A review of some recent developments in small animal SPECT instrumentations was given by Meikle [5]. These developments have benefited from recent advances in gamma ray sensor technologies, which include the high resolution CZT focal plane detector developed at the University of Arizona [6], [7], the multi-pixel Hybrid PhotoDiode (M-HPD) developed at CERN [8], [9], the double-sided silicon strip sensors developed by Peterson et al. [10], the silicon drift diode (SDD) array developed by Fiorini et al. [11], [12], the Medipix (2) based hybrid pixel sensors developed at CERN [13], [14], EMCCD based mini gamma camera developed by de Vree et al. [15], Heemskerk et al. [16], Nagarkar et al. [17], [18] and Teo et al. [19], the GEM based photon sensors coupled to scintillation materials [20], [21], the intensified EMCCD cameras developed by Meng et al. [1], [2], the scientific CCD based ultra-high resolution photon sensors[22], the large area multi-channel plate (MCP) based detectors [23], [24], the avalanche photodiode (APD) detectors reported by Yatsu et al. [25] and Shah et al. [26], and the solid-state photomultiplier (SSPM) reported by Stapels [27] etc. Some of these developments have pushed the intrinsic detector resolution to well below a hundred micrometers for detecting 27–140 keV gamma rays. Several groups have proposed or developed prototype SPECT systems that have the potential of achieving an ultra-high imaging resolution in a few hundred microns range. These include the SemiSPECT reported by Kastis [6], the SiliSPECT under development by Peterson et al. [10], the MediSPECT proposed (and evaluated) by Accorsi et al. [28], [29], the U-SPECT-III proposed by Beekman et al. [30], and a low-cost and ultra-high resolution imager based on the second generation image intensifier [31] etc. in addition, Abbott et al. has reported the use of a pre-existing SPECT camera, arranged in an extreme focusing geometry for ultra-high resolution small animal SPECT imaging applications [32].