Research And Develop On The High Spatial Resolution Animal All Digital PET Instrument

Spatial resolution is one of the important properties of positron emission tomography(PET)system.In the framework of all digital PET,the high spatial resolution animal PET instrument is researched and developed in this paper.Firstly,the factors affecting the PET system spatial are studied.Because of the small noncollinearity of animal PET,we should mainly focus on intrinsic spatial resolution.With the animal PET detector crystal getting finer,the importance of decoding factors is standed out.The concept and framework of digital PET is elaborated.Compared to traditional analog or mixed analog-digital PET,digital PET digitize scintillation pulses directly,and maximize digitization level of the data acquisition(DAQ)system.Secondly,based on silicon photomultiplier(SiPM),we started the high resolution SiPM/PET detector research and develop.From the gain,photon detection efficiency,dark count,crosstalk,afterpulse and temperature sensitive properties of SiPM,we analyze the SiPM advantages and challenges of the application in SiPM/PET detector.Through the theoretical analysis and experimental verification with the comprehensive factors of SiPM/PET detector energy resolution,the 400/mm2 microcell unit density of SiPM is most suitable for PET applications.We presented a dual energy radiation source method to optimise the nonlinearity of three different microcell density SiPM,then obtained amore correct energy spectrum and energy resolution.We presented two high resolution SiPM/PET detector front-end design,and compared four multi-channel DAQ multiplexing scheme.We choose the array crystal coupled SiPM scheme,using the symmetric charge division circuit(SCD)multiplexing circuit,and add the different temperature gain adaptive correction method to complete the optimization and implementation of the all digital PET detector based on SiPM.Thirdly,the high spatial resolution animal all digital PET detector researched and developed.With the same detection area,BDM upgrade to high spatial resolution BDM-S module.With the multi-voltage threshold(MVT)digital method,upgrade the DAQ system,software coincidence and image reconstruction on the server,to complete the implementation of high spatial resolution all digital PET detector.Further decomposing the decoding factor b to the front-end design and DAQ digital detector level two factors,we analyze a number of animal PET in three different front-end design solutions,and lists several DAQ digital systems with different levels of PET system.With the progress of the computer industry,from a purely analog circuit development to application specific integrated circuit(ASIC),then MVT digital methods with using the pulse prior information,DAQ digital level sequentially becomes higher,and the decoding factors contribute accordingly becomes smaller.Finally,After the basic detection module(BDM)with new photon electronic device SiPM and BDM with high spatial resolution developed,We integrated the whole all digital PET instrument using the all digital PET framework and the soft coincidence system.The qualitative and quantitative evaluation of the spatial resolution is measured.After the simulation and actual experiments,high spatial resolution digital PET can distinguish including 0.7 mm diameter Derenzo sectors.for the different timing shift between channels in PET system,we proposed a timing shift ring optimized method based on a cycloparaffin source.Using liquid sources used in PET usually,and with simple n(n is the number of PET channels)level of addition operation,this method can be reduced to the minimum position optimization unit to PET detectable unit.The system timing resolution enhance with this method.At the system level,corresponding to the timing resolution,we set the timing window to the time 5 ns and 2.5 ns,and draw the system NECR curve.Compared before and after the application of optimization methods,the system NECR value is improved effectively.This method can be generalized to clinical PET.