Data Readout and Processing Toolkit for Small-Size Gamma Cameras

We developed a universal data acquisition toolkit for application in small-size gamma cameras with multianode position sensitive photomultiplier tubes (PSPMTs) and with the charge division type of the front-end readout. The gamma camera readout is designed for a detector comprising an array of PSPMTs with a pad matrix anode layout. The test system consists of nine H8500 Hamamtsu photomultiplier tubes covering square area approx. 15 by 15 cm(2). Different arrangements of 1 to 16 PSPMTs utilizing similar electronics design are possible. The readout electronics includes an anode gain no-uniformity correction circuit and an analog data processing circuit that provides a charge division type of output with four analog channels. Our system uses an off-the-shelf PCI data acquisition card operating with a PCI-bus equipped computer under Linux. For better accuracy in the position resolution and extension of the data dynamic range, a multisampling data acquisition regime is used for each of the four analog inputs. Initial results of evaluation of the performance of the data readout and processing system with the test detector are presented. For the test measurements we used a NaI(Tl) pixellated scintillator crystal array with the 1.4x1.4 mm pitch. The results show a good spatial resolution mapping over 10,000 crystals of the scintillator with the Co-57 (122 keV) or Na-22 (511 keV) gamma sources. The data readout and processing system position resolution is good enough for most of the available commercial scintillator crystal arrays. The system is shown to achieve the relative position sensing better than 1%. These results confirm that our readout technique combined with our data processing methodology is suitable for use with a range of small gamma cameras of different sizes and configurations.