Aims:In this work,we evaluated the performance of three pitches positron emission tomography(PET)detectors for building a high-resolution small-animal PET imaging experimental platform.Methods:The evaluation of PET de...Aims:In this work,we evaluated the performance of three pitches positron emission tomography(PET)detectors for building a high-resolution small-animal PET imaging experimental platform.Methods:The evaluation of PET detectors includes twodimensional crystal identification,energy resolution,and crystal look-up table.The nuclear instrumentation module and PXI data acquisition(DAQ)system were both used to obtain flood images.The energy spectrum of the Na-22 source was measured.PET detectors of 2.0 and 1.6 mm pitches used in our present experiment were composed of lutetium yttrium oxyorthosilicate(LYSO)crystals directly coupled to position-sensitive photomultiplier tubes(PSPMTs).The 1.3-mm pitch detector comprises a LYSO crystal,a tapered light-guide,and a PSPMT.The crystal sizes of the detectors were a 10×10 array of 2.0×2.0×10 mm^(3) crystals,a 10×10 array of 1.6×1.6×10 mm^(3) crystals,and an 18×18 array of 1.3×1.3×10 mm^(3) crystals,respectively.Due to the lower sampling frequency of the DAQ system,a spline interpolation algorithm was introduced in the signal waveform to reconstruct the peak values.Results:The experimental results indicated that all three PET detector crystals could be clearly identified.A detailed analysis demonstrated that the key characteristic full width at half maximum(FWHM)values of the crystals profile could reach 0.46±0.03,0.32±0.03,and 0.21±0.02 mm,while the crystal average energy resolutions were 16.8%±1.76%,20.1%±2.24%,and 31.5%±3.76%,which correspond to pitches of 2.0-,1.6-,and 1.3-mm,respectively.Conclusions:The PET detector modules of LYSO crystal arrays could be potentially used in the small-animal PET imaging applications and are promising to achieve submillimeter PET images.展开更多
In this paper,a predator-prey ecosystem with two delays is considered.Firstly,the stability of the equilibrium of the system is investigated by analyzing the characteristic equation.Secondly,by choosing the sum of the...In this paper,a predator-prey ecosystem with two delays is considered.Firstly,the stability of the equilibrium of the system is investigated by analyzing the characteristic equation.Secondly,by choosing the sum of the two delays as a bifurcation parameter,it is shown that Hopf bifurcation occurs as the parameter passes through a certain critical value.Finally,in order to illustrate our theoretical analysis,some numerical simulations are also included.展开更多
基金This work was supported by National Natural Science Foundation of China(11305083)in part by the Fundamental Research Funds for the Central Universities under Grant lzujbky-2016-27。
文摘Aims:In this work,we evaluated the performance of three pitches positron emission tomography(PET)detectors for building a high-resolution small-animal PET imaging experimental platform.Methods:The evaluation of PET detectors includes twodimensional crystal identification,energy resolution,and crystal look-up table.The nuclear instrumentation module and PXI data acquisition(DAQ)system were both used to obtain flood images.The energy spectrum of the Na-22 source was measured.PET detectors of 2.0 and 1.6 mm pitches used in our present experiment were composed of lutetium yttrium oxyorthosilicate(LYSO)crystals directly coupled to position-sensitive photomultiplier tubes(PSPMTs).The 1.3-mm pitch detector comprises a LYSO crystal,a tapered light-guide,and a PSPMT.The crystal sizes of the detectors were a 10×10 array of 2.0×2.0×10 mm^(3) crystals,a 10×10 array of 1.6×1.6×10 mm^(3) crystals,and an 18×18 array of 1.3×1.3×10 mm^(3) crystals,respectively.Due to the lower sampling frequency of the DAQ system,a spline interpolation algorithm was introduced in the signal waveform to reconstruct the peak values.Results:The experimental results indicated that all three PET detector crystals could be clearly identified.A detailed analysis demonstrated that the key characteristic full width at half maximum(FWHM)values of the crystals profile could reach 0.46±0.03,0.32±0.03,and 0.21±0.02 mm,while the crystal average energy resolutions were 16.8%±1.76%,20.1%±2.24%,and 31.5%±3.76%,which correspond to pitches of 2.0-,1.6-,and 1.3-mm,respectively.Conclusions:The PET detector modules of LYSO crystal arrays could be potentially used in the small-animal PET imaging applications and are promising to achieve submillimeter PET images.
基金supported by the Foundation of Fujian Education Bureau(JB12046)
文摘In this paper,a predator-prey ecosystem with two delays is considered.Firstly,the stability of the equilibrium of the system is investigated by analyzing the characteristic equation.Secondly,by choosing the sum of the two delays as a bifurcation parameter,it is shown that Hopf bifurcation occurs as the parameter passes through a certain critical value.Finally,in order to illustrate our theoretical analysis,some numerical simulations are also included.
