An efficient implementation on a low cost FPGA for photon detection in nuclear imaging

The aim of this study is to propose and evaluate a simple, open source, data acquisition (DAQ) tool, which provides accurate results for nuclear imaging applications. For this purpose a Xilinx Spartan3E Starter Kit, which is one of the simplest Field Programmable Gate Arrays (FPGA) evaluation boards, was used. The system has been evaluated using a positionsensitive photo-multiplier (PSPMT) at the energy produced by 99m Tc sources. Two dual channel, external, 12-bit analog to digital converters (ADC) with a sampling rate of 1Msps per channel were used. The tool was designed using Xilinx's Embedded Development Kit (EDK) and was based in Xilinx's Microblaze soft-core processor. A reference multiparameter based data acquisition system using nuclear instrumentation modules (NIM) was used for the evaluation of the proposed system. Two different algorithms for pulse height estimation were applied; the maximum height approximation method and the Gaussian approximation. A second PSPMT and a Silicon Photomultiplier (SiPM) were used for further evaluation of image quality and energy spectrum respectively. Results have shown that the FPGA based data acquisition system i) provides accurate digitization of the PSPMTs anode signals in various conditions and ii) gives similar energy spectra when SiPMs are used.