Detector Characterization And Preliminary Tomography Based On High Resolution Small-animal PET Imaging System

The performance of detector is very important to imaging quality in nuclear medical imaging experiment.A high resolution small-animal positron emission tomography?PET?imaging experimental platform has been built in our laboratory.The platform is composed of detector system,nuclear instrumentation?NIM?module,data acquisition?DAQ?system and computer processing system.We use the lutetium yttrium oxyorthosilicate?LYSO?crystals in the experiment.The crystal sizes of the detectors were a 10×10 array of 2.0×2.0×10 mm³ crystals,a 10×10 array of 1.6×1.6×10 mm³crystals,and an18×18 array of 1.3×1.3×10 mm³ crystals,respectively.PET detectors of2.0 and 1.6 mm pitches used in our present experiment were composed of LYSO crystals directly coupled to position-sensitive photomultiplier tubes?PS_PMTs?.The1.3-mm pitch detector comprises a LYSO crystal,a tapered light-guide,and a PSPMT.There are two sets of DAQ systems in the experiment,which are NI₃2 asynchronous PCIe₆361 acquisition card and 8-channel synchronous ART_PXI₈501 acquisition card.The former has a maximum sampling frequency of 500 kHz,and the latter has a maximum sampling frequency of 1 MHz.Due to the asynchronous sampling of the PCI DAQ system,a spline interpolation algorithm was introduced in the signal waveform to reconstruct the peak values.we evaluated the performance of three pitches positron emission tomography?PET?detectors for building a high-resolution small-animal PET imaging experimental platform.The evaluation of PET detectors includes two-dimensional flood image,horizontal profile of the crystals,energy resolution,and crystal look-up table.In this experience,the effect of the asynchronous sampling for the crystal two-dimension flood image of PET detector is compared to that of the synchronous sampling by respectively employing PCI and PXI to collect signal with sampling frequency blow 500 kHz.The best two-dimension flood image is obtained with the sampling frequency of PXI being1 MHz.According to the experience,the FWHM of single article crystal location differentiation of the detector could reach at 0.62 mm,0.54 mm and 0.29 mm,while the pitches of detector are 2.0 mm,1.6 mm and 1.3 mm,while the crystal average energy resolutions were 16.8%±1.76%,20.1%±2.24%,and 31.5%±3.76%.In this paper,PET imaging by two coincidence detectors was studied.We use a PET simulator to record the coincidence data,and obtain the 3D PET image of a 0.37MBq Na-22 point source using these three kinds of pitches detectors.The PET detector modules of LYSO crystal arrays could be potentially used in the small-animal PET imaging applications,and are promising to achieve sub-millimeter PET images.