小动物单光子发射断层成像系统的研制
摘要
MicroSPECT系统是一个采用针孔准直器成像的高分辨率小动物SPECT系统,它的探测器系统采用4个先进的位置灵敏平板型光电倍增管H8500和1个高密度NaI闪烁晶体阵列的组成方式构建而成。闪烁晶体阵列的固有分辨率为1.65mm,实际有效的像素矩阵为54×54。使用DETECT2000程序进行闪烁晶体内光子输运过程的蒙卡模拟,在系统设计中验证了MicroSPECT系统的探测器方案的可行性,并证明了H8500光电倍增管的拼接部分的探测能力。MicroSPECT探测器的准直孔参数也基于蒙卡模拟结果进行设计。
探测器的系统前端的电子学设计,通过电阻网络的方法降低了高分辨率探测器系统的输出路数,由256路信号输出减少为4路信号输出,并针对H8500阳极输出的不均匀性做了调整。除此之外还采用特殊的设计,解决了光电倍增管和闪烁晶体阵列的耦合问题。在后端设计了高速的峰位保持电路和数据采集控制系统,以百兆以太网络为途径进行数据的传输。在计算机终端中设计了相关的采集显示控制软件和机架动作控制软件。最终每个探测器可以达到500k/s的连续计数率,转换精度为12bit,并可以满足4探测器的数据传输需要。
在探测器系统的标定与校正中,针对高密度闪烁晶体阵列输出的泛场图像使用分水岭算法进行自动分割,并使用拟人工算法进行晶体编号的识别,据此得到探测器的2D-map位置校正矩阵,并做为进一步进行均匀性校正、衰变校正和能谱校正的依据。此外,通过特殊设计的线源模型对探测系统的位置误差进行了标定。
最终通过对模型成像和对小鼠MDP骨成像实验,验证了整个系统的正确性和可靠性,得到系统的分辨率在1.6mm左右,达到了系统设计的要求,并为进一步进行小动物成像研究打下了良好的基础。
The MicroSPECT system is a high resolution small animal SPECT system withpin-hole collimetor. The detector consists four H8500 PS-PMTs and one NaI scin-tillation crystal array. The pixel size of the crystal array is 1.65mm and the e?ectivedetection matrix size is 54×54. The DETECT2000 Monte Carlo simulation programverified the MicroSPECT system detector design. The results show that the joint partsof photon multiplier tubes are still available for detection. The pin-hole parameters arealso calculated by Monte Carlo method.
A compact and accurate readout system has been developed for MicroSPECT. Us-ing resistive matrix and charge division circuit, The 256 anodes from the four H8500sare reduced to 4 signals. The gain di?erences are normalized between anodes inH8500. The readout system can achieve the counting rate at 500k/s with the precisionat 12bit for each detector and the digital part can support 4 detectors’data transporta-tion.
The computer graphic methods are used in detetor correction. The 2D-map iscalculated by a Watershed method and an auto-numbering method. We do the normal-ization correction, decay correction and energy spectrum correction after that. And theposition correcitons of the whole system are based on lines specially designed modelimaging.
The whole system was verified by a serial model imaging and mouse MDP imag-ing. The resolution of the system is between 1.6mm which measures up the designobject. We can base the system for the further investigation of small animal SPECTimaging.
探测器的系统前端的电子学设计,通过电阻网络的方法降低了高分辨率探测器系统的输出路数,由256路信号输出减少为4路信号输出,并针对H8500阳极输出的不均匀性做了调整。除此之外还采用特殊的设计,解决了光电倍增管和闪烁晶体阵列的耦合问题。在后端设计了高速的峰位保持电路和数据采集控制系统,以百兆以太网络为途径进行数据的传输。在计算机终端中设计了相关的采集显示控制软件和机架动作控制软件。最终每个探测器可以达到500k/s的连续计数率,转换精度为12bit,并可以满足4探测器的数据传输需要。
在探测器系统的标定与校正中,针对高密度闪烁晶体阵列输出的泛场图像使用分水岭算法进行自动分割,并使用拟人工算法进行晶体编号的识别,据此得到探测器的2D-map位置校正矩阵,并做为进一步进行均匀性校正、衰变校正和能谱校正的依据。此外,通过特殊设计的线源模型对探测系统的位置误差进行了标定。
最终通过对模型成像和对小鼠MDP骨成像实验,验证了整个系统的正确性和可靠性,得到系统的分辨率在1.6mm左右,达到了系统设计的要求,并为进一步进行小动物成像研究打下了良好的基础。
The MicroSPECT system is a high resolution small animal SPECT system withpin-hole collimetor. The detector consists four H8500 PS-PMTs and one NaI scin-tillation crystal array. The pixel size of the crystal array is 1.65mm and the e?ectivedetection matrix size is 54×54. The DETECT2000 Monte Carlo simulation programverified the MicroSPECT system detector design. The results show that the joint partsof photon multiplier tubes are still available for detection. The pin-hole parameters arealso calculated by Monte Carlo method.
A compact and accurate readout system has been developed for MicroSPECT. Us-ing resistive matrix and charge division circuit, The 256 anodes from the four H8500sare reduced to 4 signals. The gain di?erences are normalized between anodes inH8500. The readout system can achieve the counting rate at 500k/s with the precisionat 12bit for each detector and the digital part can support 4 detectors’data transporta-tion.
The computer graphic methods are used in detetor correction. The 2D-map iscalculated by a Watershed method and an auto-numbering method. We do the normal-ization correction, decay correction and energy spectrum correction after that. And theposition correcitons of the whole system are based on lines specially designed modelimaging.
The whole system was verified by a serial model imaging and mouse MDP imag-ing. The resolution of the system is between 1.6mm which measures up the designobject. We can base the system for the further investigation of small animal SPECTimaging.
引文
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[3] McElroy D P, MacDonald L R, Beekman F J, et al. Performance evaluation of A-SPECT: Ahigh resolution desktop pinhole SPECT system for imaging small animals. IEEE TRANS-ACTIONS ON NUCLEAR SCIENCE, 2002, 49(5):2139–2147.
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[5] Barrett H H, Hunter W C J. Detectors for small-animal SPECT I: Overview of technologies.SMALL ANIMAL SPECT IMAGING, 2005. 9–48.
[6] Furenlid L R, Wilson D W, Chen Y C, et al. FastSPECT II: A second-generation high-resolution dynamic SPECT imager. IEEE TRANSACTIONS ON NUCLEAR SCIENCE,2004, 51(3):631–635.
[7] Kim H, Furenlid L R, Crawford M J, et al. SemiSPECT: A small-animal single-photonemission computed tomography (SPECT) imager based on eight cadmium zinc telluride(CZT) detector arrays. MEDICAL PHYSICS, 2006, 33(2):465–474.
[8] Metzler S D, Jaszczak R J, Patil N H, et al. Molecular imaging of small animals with a triple-head SPECT system using pinhole collimation. IEEE TRANSACTIONS ON MEDICALIMAGING, 2005, 24(7):853–862.
[9] Jaszczak R J, Li J, Wang H, et al. Pinhole collimation for ultra-high-resolution, small-field-of-view SPECT. Physics in Medicine and Biology, 1994, 39(3):425–437.
[10] Meikle S R, Fulton R R, Eberl S, et al. An investigation of coded aperture imaging for smallanimal SPECT. IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 2001, 48(3):816–821.
[11] Meikle S R, Kench P, Weisenberger A G, et al. A prototype coded aperture detector for smallanimal SPECT. IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 2002, 49(5):2167–2171.
[12] Meikle S R, Kench P, Wojcik R, et al. Performance evaluation of a multipinhole smallanimal SPECT system. 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCERECORD, VOLS 1-5, 2004. 1988–1992.
[13] Meikle S R, Wojcik R, Weisenberger A G, et al. CoALA-SPECT: A coded aperture labo-ratory animal SPECT system for pre clinical imaging. 2002 IEEE NUCLEAR SCIENCESYMPOSIUM, CONFERENCE RECORD, VOLS 1-3, 2003. 1061–1065.
[14] Smith M F, Meikle S R, Majewski S, et al. Design of multipinhole collimators forsmall animal SPECT. 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCERECORD, VOLS 1-5, 2004. 2291–2295.
[15] Schramm N, Schurrat T, Behe M, et al. Multi-pinhole small animal SPECT. EUROPEANJOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING, 2004, 31:S236–S236.
[16] Schramm N, Wirrwar A, Sonnenberg F, et al. Compact high resolution detector for smallanimal SPECT. IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 2000, 47(3):1163–1167.
[17] Schramm N, Wirrwar A, Sonnenberg F, et al. Compact high resolution detector for small an-imal SPECT. 1999 IEEE NUCLEAR SCIENCE SYMPOSIUMCONFERENCE RECORD,VOLS 1-3, 1999. 1479–1482.
[18] Schramm N U, Behe M, Schurrat T, et al. Multi-pinhole spect: Recent results of an animalimaging system. JOURNAL OF NUCLEAR MEDICINE, 2003, 44(5):9P–10P.
[19] Schramm N U, Ebel G, Engeland U, et al. High-resolution SPECT using multipinholecollimation. IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 2003, 50(3):315–320.
[20] Schramm N U, Engeland U, Ebel G, et al. Multi-pinhole SPECT for small animal research.JOURNAL OF NUCLEAR MEDICINE, 2002, 43(5):223P–223P.
[21] Schramm N U, Pissarek M, Hoppin J, et al. HiSPECT: High-resolution small animal SPECTin pharmacological research. NAUNYN-SCHMIEDEBERGS ARCHIVES OF PHARMA-COLOGY, 2005, 371:390.
[22] Schramm N U, Schipper M, Schurrat T, et al. Performance of a multi-pinhole animalSPECT. 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCE RECORD,VOLS 1-5, 2004. 2077–2079.
[23] Beekman F, Have F. The pinhole: gateway to ultra-high-resolution three-dimensional ra-dionuclide imaging. EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLEC-ULAR IMAGING, 2007, 34(2):151–161.
[24] Beekman F J, Vastenhouw B. Design and simulation of a high-resolution stationary SPECTsystem for small animals. PHYSICS IN MEDICINE AND BIOLOGY, 2004, 49(19):4579–4592.
[25] Beekman F J, Have F, Vastenhouw B, et al. U-SPECT-I: A Novel System for Submillimeter-Resolution Tomography with Radiolabeled Molecules in Mice. J Nucl Med, 2005,46(7):1194–1200.
[26] Accorsi R, Gasparini F, Lanza R C. A coded aperture for high-resolution nuclear medicineplanar imaging with a conventional anger camera: Experimental results. IEEE TRANSAC-TIONS ON NUCLEAR SCIENCE, 2001, 48(6):2411–2417.
[27] Accorsi R, Gasparini F, Lanza R C. Optimal coded aperture patterns for improved SNRin nuclear medicine imaging. NUCLEAR INSTRUMENTS & METHODS IN PHYSICSRESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS ANDASSOCIATED EQUIPMENT, 2001, 474(3):273–284.
[28] Accorsi R, Lanza R C. Near-field artifact reduction in planar coded aperture imaging.APPLIED OPTICS, 2001, 40(26):4697–4705.
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