采用三阶信噪比(signal to interference ratio,SIR)干扰谐振器作为基本谐振单元,通过调整阻抗比控制主频和第一杂散频率的位置,设计了一种新型高阻带抑制双通带滤波器.滤波器第一通带由主谐振频率产生,第二通带由第一杂散频率产生.运...采用三阶信噪比(signal to interference ratio,SIR)干扰谐振器作为基本谐振单元,通过调整阻抗比控制主频和第一杂散频率的位置,设计了一种新型高阻带抑制双通带滤波器.滤波器第一通带由主谐振频率产生,第二通带由第一杂散频率产生.运用三角耦合结构作为该滤波器的拓扑结构,使得整体滤波器呈现出带外传输零点和阻带的高抑制度.使用交指型耦合结构实现输入/输出端的强耦合,得到较高的外部品质因数.该滤波器的两个通带中心频率分别为1.57 GHz(GPS)和2.5 GHz(4G),3 d B带宽分别为4.0%和2.4%.结果表明,测量结果和仿真结果基本吻合.展开更多
Background Cervical spondylotic myelopathy （CSM） is a common cause of disability in elderly patients.Previous studies have shown that spinal cord cell apoptosis due to spinal cord compression plays an important role...Background Cervical spondylotic myelopathy （CSM） is a common cause of disability in elderly patients.Previous studies have shown that spinal cord cell apoptosis due to spinal cord compression plays an important role in the pathology of myelopathy.Although changes in magnetic resonance imaging （MRI） T2 signal intensity ratio （SIR） are considered to be an indicator of CSM,little information is published supporting the correlation between changes in MRI signal and pathological changes.This study aims to testify the correlation between MRI T2 SIR changes and cell apoptosis using a CSM animal model.Methods Forty-eight rabbits were randomly assigned to four groups：one control group and three experimental chronic compression groups,with each group containing 12 animals.Chronic compression of the cervical spinal cord was implemented in the experimental groups by implanting a screw in the C3 vertebra.The control group underwent sham surgery.Experimental groups were observed for 3,6,or 9 months after surgery.MRI T2-weighted SIR Tarlov motor scores and cortical somatosensory-evoked potentials （CSEPs） were periodically monitored.At each time point,rabbits from one group were sacrificed to determine the level of apoptosis by histology （n=6） and Western blotting （n=6）.Results Tarlov motor scores in the compression groups were lower at all time points than the control group scores,with the lowest score at 9 months （P ＜0.001）.Electrophysiological testing showed a significantly prolonged latency in CSEP in the compression groups compared with the control group.All rabbits in the compression groups showed higher MRI T2 SIR in the injury epicenter compared with controls,and higher SIR was also found at 9 months compared with 3 or 6 months.Histological analysis showed significant apoptosis in the spinal cord tissue in the compression groups,but not in the control group.There were significant differences in apoptosis degree over time （P ＜0.001）,with the 9-month group displaying the most severe spinal cord apoptosis.Spearman＇s rank correlation test showed that there was close relation between MRI SIR and degree of caspase-3 expression in Western blotting （r=0.824.P ＜0.001）.Conclusions Clear apoptosis of spinal cord tissue was observed during chronic focal spinal compression.Changes in MRI T2 SIR mav be related to the severity of the apoptosis in cervical spinal cord.展开更多
Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its p...Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its potential value. The aim of this study was to investigate the correlation between ISI position and the outcome of surgical treatment for cervical spondylotic myelopathy （CSM） patients. Methods A retrospective study was conducted. Pre- and post-operative clinical status was evaluated by modified Japanese Orthopaedic Association （JOA） score. ISI was evaluated according to the T2-weighted sequences. The JOA score and the recovery ratios among patients with ISI in gray matter （group A）, in both gray and white matter （group B）, and ISI-negative group were compared. Results Totally 64 patients were enrolled in this retrospective study. Preoperative JOA score of ISI positive and negative group had significant difference, but the recovery ratios had no significant difference （the recovery ratios of the two groups in week 1, week 26, and week 104 were （21.54±14.65）%, （50.56±14.76）%, （59.23±13.08）% and （20.25±14.32）%, （54.46±3.16）% and （61.26±29.4）%, respectively; P 〉0.05）. The recovery ratios of negative group and group A in week 104 were superior to group B （the recovery ratios of negative group, group A, and group B in week 104 were （61.26±29.49）%, （65.35±11.36）%, and （50.33±10.20）%, respectively; P 〈0.05）. Conclusions Patients with ISI in the gray matter alone on T2-weighted MR images did not have significantly different surgical outcomes compared with those without ISI. Patients with ISI in both gray and white matter had surgical outcomes that were worse than those without ISI.展开更多
文摘采用三阶信噪比(signal to interference ratio,SIR)干扰谐振器作为基本谐振单元,通过调整阻抗比控制主频和第一杂散频率的位置,设计了一种新型高阻带抑制双通带滤波器.滤波器第一通带由主谐振频率产生,第二通带由第一杂散频率产生.运用三角耦合结构作为该滤波器的拓扑结构,使得整体滤波器呈现出带外传输零点和阻带的高抑制度.使用交指型耦合结构实现输入/输出端的强耦合,得到较高的外部品质因数.该滤波器的两个通带中心频率分别为1.57 GHz(GPS)和2.5 GHz(4G),3 d B带宽分别为4.0%和2.4%.结果表明,测量结果和仿真结果基本吻合.
基金This study was supported by a grant from the National Natural Science Foundation of China （No. 81071510）.
文摘Background Cervical spondylotic myelopathy （CSM） is a common cause of disability in elderly patients.Previous studies have shown that spinal cord cell apoptosis due to spinal cord compression plays an important role in the pathology of myelopathy.Although changes in magnetic resonance imaging （MRI） T2 signal intensity ratio （SIR） are considered to be an indicator of CSM,little information is published supporting the correlation between changes in MRI signal and pathological changes.This study aims to testify the correlation between MRI T2 SIR changes and cell apoptosis using a CSM animal model.Methods Forty-eight rabbits were randomly assigned to four groups：one control group and three experimental chronic compression groups,with each group containing 12 animals.Chronic compression of the cervical spinal cord was implemented in the experimental groups by implanting a screw in the C3 vertebra.The control group underwent sham surgery.Experimental groups were observed for 3,6,or 9 months after surgery.MRI T2-weighted SIR Tarlov motor scores and cortical somatosensory-evoked potentials （CSEPs） were periodically monitored.At each time point,rabbits from one group were sacrificed to determine the level of apoptosis by histology （n=6） and Western blotting （n=6）.Results Tarlov motor scores in the compression groups were lower at all time points than the control group scores,with the lowest score at 9 months （P ＜0.001）.Electrophysiological testing showed a significantly prolonged latency in CSEP in the compression groups compared with the control group.All rabbits in the compression groups showed higher MRI T2 SIR in the injury epicenter compared with controls,and higher SIR was also found at 9 months compared with 3 or 6 months.Histological analysis showed significant apoptosis in the spinal cord tissue in the compression groups,but not in the control group.There were significant differences in apoptosis degree over time （P ＜0.001）,with the 9-month group displaying the most severe spinal cord apoptosis.Spearman＇s rank correlation test showed that there was close relation between MRI SIR and degree of caspase-3 expression in Western blotting （r=0.824.P ＜0.001）.Conclusions Clear apoptosis of spinal cord tissue was observed during chronic focal spinal compression.Changes in MRI T2 SIR mav be related to the severity of the apoptosis in cervical spinal cord.
文摘Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its potential value. The aim of this study was to investigate the correlation between ISI position and the outcome of surgical treatment for cervical spondylotic myelopathy （CSM） patients. Methods A retrospective study was conducted. Pre- and post-operative clinical status was evaluated by modified Japanese Orthopaedic Association （JOA） score. ISI was evaluated according to the T2-weighted sequences. The JOA score and the recovery ratios among patients with ISI in gray matter （group A）, in both gray and white matter （group B）, and ISI-negative group were compared. Results Totally 64 patients were enrolled in this retrospective study. Preoperative JOA score of ISI positive and negative group had significant difference, but the recovery ratios had no significant difference （the recovery ratios of the two groups in week 1, week 26, and week 104 were （21.54±14.65）%, （50.56±14.76）%, （59.23±13.08）% and （20.25±14.32）%, （54.46±3.16）% and （61.26±29.4）%, respectively; P 〉0.05）. The recovery ratios of negative group and group A in week 104 were superior to group B （the recovery ratios of negative group, group A, and group B in week 104 were （61.26±29.49）%, （65.35±11.36）%, and （50.33±10.20）%, respectively; P 〈0.05）. Conclusions Patients with ISI in the gray matter alone on T2-weighted MR images did not have significantly different surgical outcomes compared with those without ISI. Patients with ISI in both gray and white matter had surgical outcomes that were worse than those without ISI.
