The frequency–space（f–x） empirical mode decomposition（EMD） denoising method has two limitations when applied to nonstationary seismic data. First, subtracting the first intrinsic mode function（IMF） results in ...The frequency–space（f–x） empirical mode decomposition（EMD） denoising method has two limitations when applied to nonstationary seismic data. First, subtracting the first intrinsic mode function（IMF） results in signal damage and limited denoising. Second, decomposing the real and imaginary parts of complex data may lead to inconsistent decomposition numbers. Thus, we propose a new method named f–x spatial projection-based complex empirical mode decomposition（CEMD） prediction filtering. The proposed approach directly decomposes complex seismic data into a series of complex IMFs（CIMFs） using the spatial projection-based CEMD algorithm and then applies f–x predictive filtering to the stationary CIMFs to improve the signal-to-noise ratio. Synthetic and real data examples were used to demonstrate the performance of the new method in random noise attenuation and seismic signal preservation.展开更多
目的探讨^(18)F-脱氧葡萄糖(^(18)F-fluorodeoxyglucose,^(18)F-FDG)正电子发射计算机断层扫描(positron emission tomography/computed tomography,PET/CT)联合功能磁共振成像(function magnetic resonance imaging,fMRI)在原发性中枢...目的探讨^(18)F-脱氧葡萄糖(^(18)F-fluorodeoxyglucose,^(18)F-FDG)正电子发射计算机断层扫描(positron emission tomography/computed tomography,PET/CT)联合功能磁共振成像(function magnetic resonance imaging,fMRI)在原发性中枢神经系统淋巴瘤(primary central nervous system lymphoma,PCNSL)中的诊断价值。方法回顾性分析17例PCNSL患者PET/CT影像学特征[最大标准摄取值(standard uptake value maximum,SUVmax),平均标准摄取值(standard uptake value maximum mean,SUVmean)]及其中10例患者功能磁共振影像学特征[磁共振扩散加权成像(diffusion weighted imaging,DWI),磁共振灌注成像(perfusion weighted imaging,PWI)],同时统计14例Ⅲ~Ⅵ级胶质瘤和14例脑转移瘤患者PET/CT影像学特征(SUVmax、SUVmean),绘制PCNSL组与脑胶质瘤、转移瘤联合组的SUVmax及SUVmean受试者工作特征曲线(receiver operator characteristic curve,ROC),确定诊断最优阈值,观察10例原发性中枢神经系统淋巴瘤患者ADC病灶平均值与SUVmax及SUVmean的相关性。结果17例淋巴瘤组共28个病灶,10例具有MRI影像资料患者,共15个病灶。淋巴瘤组与胶质瘤、转移瘤联合组SUVmax(t=0)、SUVmean(t=0)差异有统计学意义。根据ROC曲线分析,SUVmax曲线下面积AUC:0.836,取截断值SUVmax为17.55时,敏感性0.765,特异性0.821;SUVmean曲线下面积AUC:0.853,取截断值SUVmean为11.9时,敏感性0.882,特异性0.75。10例具有MRI影像资料的PCNSL患者,病灶PWI呈低灌注13例,等灌注2例,DWI弥散受限,且平均ADC值与SUVmax(r=—0.725,P=0.018)及SUVmean(r=—0.666,P=0.036)呈负相关。结论原发性中枢神经系统淋巴瘤^(18)F-FDG PET/CT摄取程度高于胶质瘤组和转移瘤组,且SUVmax 17.55和SUVmean 11.9可作为参考诊断阈值,指导淋巴瘤与其他颅内常见肿瘤(胶质瘤和转移瘤)的鉴别,结合其功能MRI弥散受限及灌注减低等特点更有助于提高PCNSL诊断特异性。展开更多
For a function y=f(x)to have an inverse function,f must be one-to-one.Then for each x in its domian there is exactly one y in its range;furthermore,to each y in the range,there corresponds exactly one x in the domain....For a function y=f(x)to have an inverse function,f must be one-to-one.Then for each x in its domian there is exactly one y in its range;furthermore,to each y in the range,there corresponds exactly one x in the domain.The correspondence from the展开更多
基金supported financially by the National Natural Science Foundation(No.41174117)the Major National Science and Technology Projects(No.2011ZX05031–001)
文摘The frequency–space（f–x） empirical mode decomposition（EMD） denoising method has two limitations when applied to nonstationary seismic data. First, subtracting the first intrinsic mode function（IMF） results in signal damage and limited denoising. Second, decomposing the real and imaginary parts of complex data may lead to inconsistent decomposition numbers. Thus, we propose a new method named f–x spatial projection-based complex empirical mode decomposition（CEMD） prediction filtering. The proposed approach directly decomposes complex seismic data into a series of complex IMFs（CIMFs） using the spatial projection-based CEMD algorithm and then applies f–x predictive filtering to the stationary CIMFs to improve the signal-to-noise ratio. Synthetic and real data examples were used to demonstrate the performance of the new method in random noise attenuation and seismic signal preservation.
文摘目的探讨^(18)F-脱氧葡萄糖(^(18)F-fluorodeoxyglucose,^(18)F-FDG)正电子发射计算机断层扫描(positron emission tomography/computed tomography,PET/CT)联合功能磁共振成像(function magnetic resonance imaging,fMRI)在原发性中枢神经系统淋巴瘤(primary central nervous system lymphoma,PCNSL)中的诊断价值。方法回顾性分析17例PCNSL患者PET/CT影像学特征[最大标准摄取值(standard uptake value maximum,SUVmax),平均标准摄取值(standard uptake value maximum mean,SUVmean)]及其中10例患者功能磁共振影像学特征[磁共振扩散加权成像(diffusion weighted imaging,DWI),磁共振灌注成像(perfusion weighted imaging,PWI)],同时统计14例Ⅲ~Ⅵ级胶质瘤和14例脑转移瘤患者PET/CT影像学特征(SUVmax、SUVmean),绘制PCNSL组与脑胶质瘤、转移瘤联合组的SUVmax及SUVmean受试者工作特征曲线(receiver operator characteristic curve,ROC),确定诊断最优阈值,观察10例原发性中枢神经系统淋巴瘤患者ADC病灶平均值与SUVmax及SUVmean的相关性。结果17例淋巴瘤组共28个病灶,10例具有MRI影像资料患者,共15个病灶。淋巴瘤组与胶质瘤、转移瘤联合组SUVmax(t=0)、SUVmean(t=0)差异有统计学意义。根据ROC曲线分析,SUVmax曲线下面积AUC:0.836,取截断值SUVmax为17.55时,敏感性0.765,特异性0.821;SUVmean曲线下面积AUC:0.853,取截断值SUVmean为11.9时,敏感性0.882,特异性0.75。10例具有MRI影像资料的PCNSL患者,病灶PWI呈低灌注13例,等灌注2例,DWI弥散受限,且平均ADC值与SUVmax(r=—0.725,P=0.018)及SUVmean(r=—0.666,P=0.036)呈负相关。结论原发性中枢神经系统淋巴瘤^(18)F-FDG PET/CT摄取程度高于胶质瘤组和转移瘤组,且SUVmax 17.55和SUVmean 11.9可作为参考诊断阈值,指导淋巴瘤与其他颅内常见肿瘤(胶质瘤和转移瘤)的鉴别,结合其功能MRI弥散受限及灌注减低等特点更有助于提高PCNSL诊断特异性。
文摘For a function y=f(x)to have an inverse function,f must be one-to-one.Then for each x in its domian there is exactly one y in its range;furthermore,to each y in the range,there corresponds exactly one x in the domain.The correspondence from the
