The fusion neutron penumbral imaging system Monte Carlo model was established. The transfer functions of the two discrete units in the neutron source were obtained in two situations: Imaging in geometrical near-optica...The fusion neutron penumbral imaging system Monte Carlo model was established. The transfer functions of the two discrete units in the neutron source were obtained in two situations: Imaging in geometrical near-optical and real situation. The spatial resolutions of the imaging system in two situations were evaluated and compared. The penumbral images of four units in the source were obtained by means of 2-dimensional (2D) convolution and Monte Carlo simulation. The penumbral images were reconstructed with the same method of filter. The same results were confirmed. The encoding essence of penumbral imaging was revealed. With MCNP(Monte Carlo N-particle) simulation, the neutron penumbral images of the large area source (200 μm×200 μm) on scintillation fiber array were obtained. The improved Wiener filter method was used to reconstruct the penumbral image and the source image was obtained. The results agree with the preset neutron source image. The feasibility of the neutron imaging system was verified.展开更多
Objective:To study the changes of nitric oxide synthase(NOS)activity in penumbral and core area during focal cerebral ischemia and reperfusion,and to explore the therapeutic window of focal cerebral ischemia. Methods...Objective:To study the changes of nitric oxide synthase(NOS)activity in penumbral and core area during focal cerebral ischemia and reperfusion,and to explore the therapeutic window of focal cerebral ischemia. Methods:The middle cerebral artery of rats was occluded for 15,30,60,90 and 120 min by an intraluminal filament respectively,and recirculation was instituted for 24 h.The changes of NOS activity in ischemic core area(parietal cortex and caudoputamen)and penumbral area (frontal cortex)were examined after focal cerebral ischemia and reperfusion using NADPH-d histochemistry technique.Results:The NOS activity of the ischemic penumbral area peaked at 60 min while the ischemic core area peaked at 30 min then declined at 90-120 min sharply.Conclusion:NOS takes part in cerebral ischemic damage during focal cerebral ischemia and reperfusion.The NOS activity of the ischemic penumbral area is different from the ischemic core area.The peak time of the penumbral area is delayed comparing with the core area.The data suggest that the best time to apply NOS inhibitor is within 30 min in ischemic core area, and 60 min in penumbral area.展开更多
基金Supported by the NSAF Joint Fund set up by NSFC and CAEP (Grant No. 10576022)
文摘The fusion neutron penumbral imaging system Monte Carlo model was established. The transfer functions of the two discrete units in the neutron source were obtained in two situations: Imaging in geometrical near-optical and real situation. The spatial resolutions of the imaging system in two situations were evaluated and compared. The penumbral images of four units in the source were obtained by means of 2-dimensional (2D) convolution and Monte Carlo simulation. The penumbral images were reconstructed with the same method of filter. The same results were confirmed. The encoding essence of penumbral imaging was revealed. With MCNP(Monte Carlo N-particle) simulation, the neutron penumbral images of the large area source (200 μm×200 μm) on scintillation fiber array were obtained. The improved Wiener filter method was used to reconstruct the penumbral image and the source image was obtained. The results agree with the preset neutron source image. The feasibility of the neutron imaging system was verified.
文摘Objective:To study the changes of nitric oxide synthase(NOS)activity in penumbral and core area during focal cerebral ischemia and reperfusion,and to explore the therapeutic window of focal cerebral ischemia. Methods:The middle cerebral artery of rats was occluded for 15,30,60,90 and 120 min by an intraluminal filament respectively,and recirculation was instituted for 24 h.The changes of NOS activity in ischemic core area(parietal cortex and caudoputamen)and penumbral area (frontal cortex)were examined after focal cerebral ischemia and reperfusion using NADPH-d histochemistry technique.Results:The NOS activity of the ischemic penumbral area peaked at 60 min while the ischemic core area peaked at 30 min then declined at 90-120 min sharply.Conclusion:NOS takes part in cerebral ischemic damage during focal cerebral ischemia and reperfusion.The NOS activity of the ischemic penumbral area is different from the ischemic core area.The peak time of the penumbral area is delayed comparing with the core area.The data suggest that the best time to apply NOS inhibitor is within 30 min in ischemic core area, and 60 min in penumbral area.
文摘目的探讨CT灌注参数图像标准化匹配技术对梗死后脑组织的缺血状态及确定客观半暗带的评估作用。方法对缺血性卒中患者40例行常规CT灌注检查,重建数据后根据脑血容量(cerebral blood volume,CBV)、脑血流量(cerebral blood flow,CBF)、达峰时间(time to peak,TTP)参数分别确定彻底坏死区(non variable tissue,NVT)、严重缺血区(tissue at risk,TAR)、相对缺血区(relative ischemic tissue,RIT)阈值及在脑组织的绝对面积大小,并将3个区域CBF、CBV、TTP参数进行图像匹配,对匹配结果进行分析。结果坏死边缘、严重缺血区、相对缺血区边缘阈值分别为CBV=1.7 m L/100 g、CBF=30.0 m L/(100 g·min)、TTP=9.5 s。图像匹配后可清楚分辨出急性期缺血区的坏死区以及严重缺血区、相对缺血区构成的缺血半暗带并可进行量化面积。匹配后复合性单病灶常见RIT>NVT>TAR、NVT>TAR>RIT,皮质下单病灶组RIT>NVT>TAR或NVT>RIT>TAR,多发梗死病灶组RIT>NVT>TAR、NVT>TAR>RIT。结论利用图像标准化匹配方法可以通过CBV、CBF、TTP参数量化评估病灶的NVT、TAR和RIT区域,直观显示缺血半暗带面积,为临床治疗缺血性卒中提供个体化影像评估技术。
