In conventional PET systems,the parallax error degrades image resolution and causes image distortion.To remedy this,a PET ring diameter has to be much larger than the required size of field of view(FOV),and therefore ...In conventional PET systems,the parallax error degrades image resolution and causes image distortion.To remedy this,a PET ring diameter has to be much larger than the required size of field of view(FOV),and therefore the cost goes up.Measurement of depth-of-interaction(DOI)information is effective to reduce the parallax error and improve the image quality.This study is aimed at developing a practical method to incorporate DOI information in PET sinogram generation and image reconstruction processes and evaluate its efficacy through Monte Carlo simulation.An animal PET system with 30-mm long LSO crystals and 2-mm DOI measurement accuracy was simulated and list-mode PET data were collected.A sinogram generation method was proposed to bin each coincidence event to the correct LOR location according to both incident crystal indices and DOI positions of the two annihilation photons.The sinograms were reconstructed with an iterative OSMAPEM(ordered subset maximum a posteriori expectation maximization)algorithm.Two phantoms(a rod source phantom and a Derenzo phantom)were simulated,and the benefits of DOI were investigated in terms of reconstructed source diameter(FWHM)and source positioning accuracy.The results demonstrate that the proposed method works well to incorporate DOI information in data processing,which not only overcomes the image distortion problem but also significantly improves image resolution and resolution uniformity and results in satisfactory image quality.展开更多
To increase spatial resolution and signal-to-noise ratio in PET imaging,we present in this paper the design and performance evaluation of a PET detector module combining both depth-of-interaction(DOI) and time-offligh...To increase spatial resolution and signal-to-noise ratio in PET imaging,we present in this paper the design and performance evaluation of a PET detector module combining both depth-of-interaction(DOI) and time-offlight(TOF) capabilities.The detector module consists of a staggered dual-layer LYSO block with2 mm × 2 mm × 7 mm crystals.MR-compatible SiPM sensors(MicroFJ-30035-TSV,SensL) are assembled into an 8× 8 array.SiPM signals from both fast and slow outputs are read out by a 128-channel ASIC chip.To test its performance,a flood histogram is acquired with a ^(22)Na point source on top of the detector,and the energy resolution and the coincidence resolving time(CRT) value for each individual crystal are measured.The flood histogram shows excellent crystal separation in both layers.The average energy resolution at 511 keV is 14.0 and 12.7%at the bottom and top layers,respectively.The average CRT of a single crystal is 635 and 565 ps at the bottom and top layers,respectively.In conclusion,the compact DOI-TOF PET detector module is of excellent crystal identification capability,good energy resolution and reasonable time resolution and has promising application prospective in clinical TOF PET,PET/MRI,and brain PET systems.展开更多
直流电法有效探测深度的确定是地球物理电法研究的焦点,其与最终数据解释的可靠程度紧密相连,不准确的探测深度可能会造成漏解释或过度解释.修正的DOI(Depth of Investigation)方法被用于确定直流电法的有效探测深度.该方法是在DOI法的...直流电法有效探测深度的确定是地球物理电法研究的焦点,其与最终数据解释的可靠程度紧密相连,不准确的探测深度可能会造成漏解释或过度解释.修正的DOI(Depth of Investigation)方法被用于确定直流电法的有效探测深度.该方法是在DOI法的基础上提出,针对原始采集数据的两个不同电阻率参考模型的反演结果,利用统计学方法和无约束非线性优化方法处理数据,最终得到透明索引指标,从而获得有效探测深度边界.该方法有效规避了人为选用截断阈值来确定有效探测深度的缺点.在工程实例应用上也取得了较好的效果,这对未来直流电法有效探测深度的确定具有重要应用价值.展开更多
基金Supported by Specialized Research Fund of the Doctoral Program of Higher Education(SRFDP 200800031071 )National Natural Science Foundation of China (No.10975086)National High Technology Research and Development Program("863"Program) of China(No.2006AA020802)
文摘In conventional PET systems,the parallax error degrades image resolution and causes image distortion.To remedy this,a PET ring diameter has to be much larger than the required size of field of view(FOV),and therefore the cost goes up.Measurement of depth-of-interaction(DOI)information is effective to reduce the parallax error and improve the image quality.This study is aimed at developing a practical method to incorporate DOI information in PET sinogram generation and image reconstruction processes and evaluate its efficacy through Monte Carlo simulation.An animal PET system with 30-mm long LSO crystals and 2-mm DOI measurement accuracy was simulated and list-mode PET data were collected.A sinogram generation method was proposed to bin each coincidence event to the correct LOR location according to both incident crystal indices and DOI positions of the two annihilation photons.The sinograms were reconstructed with an iterative OSMAPEM(ordered subset maximum a posteriori expectation maximization)algorithm.Two phantoms(a rod source phantom and a Derenzo phantom)were simulated,and the benefits of DOI were investigated in terms of reconstructed source diameter(FWHM)and source positioning accuracy.The results demonstrate that the proposed method works well to incorporate DOI information in data processing,which not only overcomes the image distortion problem but also significantly improves image resolution and resolution uniformity and results in satisfactory image quality.
基金supported in part by Fundamental Research Funds for the Central Universities(No.FRF-TP-15-114A1)National Natural Science Foundation of China(Nos.11375096,11505300)Tsinghua University Initiative Scientific Research Program(No.20131089289)
文摘To increase spatial resolution and signal-to-noise ratio in PET imaging,we present in this paper the design and performance evaluation of a PET detector module combining both depth-of-interaction(DOI) and time-offlight(TOF) capabilities.The detector module consists of a staggered dual-layer LYSO block with2 mm × 2 mm × 7 mm crystals.MR-compatible SiPM sensors(MicroFJ-30035-TSV,SensL) are assembled into an 8× 8 array.SiPM signals from both fast and slow outputs are read out by a 128-channel ASIC chip.To test its performance,a flood histogram is acquired with a ^(22)Na point source on top of the detector,and the energy resolution and the coincidence resolving time(CRT) value for each individual crystal are measured.The flood histogram shows excellent crystal separation in both layers.The average energy resolution at 511 keV is 14.0 and 12.7%at the bottom and top layers,respectively.The average CRT of a single crystal is 635 and 565 ps at the bottom and top layers,respectively.In conclusion,the compact DOI-TOF PET detector module is of excellent crystal identification capability,good energy resolution and reasonable time resolution and has promising application prospective in clinical TOF PET,PET/MRI,and brain PET systems.
文摘直流电法有效探测深度的确定是地球物理电法研究的焦点,其与最终数据解释的可靠程度紧密相连,不准确的探测深度可能会造成漏解释或过度解释.修正的DOI(Depth of Investigation)方法被用于确定直流电法的有效探测深度.该方法是在DOI法的基础上提出,针对原始采集数据的两个不同电阻率参考模型的反演结果,利用统计学方法和无约束非线性优化方法处理数据,最终得到透明索引指标,从而获得有效探测深度边界.该方法有效规避了人为选用截断阈值来确定有效探测深度的缺点.在工程实例应用上也取得了较好的效果,这对未来直流电法有效探测深度的确定具有重要应用价值.
