目的探究上腹部能谱CT智能匹配技术在提高图像对比噪声比(CNR)、降低对比剂使用量中的应用。方法选取行上腹部CT平扫以及双期增强扫描患者126例,分为实验组和对照组,各63例。实验组应用上腹部能谱CT智能匹配技术,对比剂含碘量为300 mg/...目的探究上腹部能谱CT智能匹配技术在提高图像对比噪声比(CNR)、降低对比剂使用量中的应用。方法选取行上腹部CT平扫以及双期增强扫描患者126例,分为实验组和对照组,各63例。实验组应用上腹部能谱CT智能匹配技术,对比剂含碘量为300 mg/kg,并采用滤波反投影法(FBP)获得A组图像;然后采用自适应统计迭代重组技术(AISR)获得B组图像。对照组采用常规CT平扫模式(120 k Vp),对比剂含碘量为450 mg/kg,采用FBP获得C组图像。比较三组图像在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像噪声以及肝、胰、门静脉、腹主动脉的CNR,并对三组图像进行评分。结果三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像噪声比较,差异均有统计学意义(F分别=187.72、246.35、51.98、127.50、23.15、48.96,P均<0.05)。两两比较结果显示,在40ke V动脉期和门静脉期,C组图像噪声低于B组和A组(q分别=8.32、9.37,P均<0.05);在50ke V动脉期和门静脉期时,B组和C组图像噪声均明显低于A组(q分别=5.73、6.84,P均<0.05);在60 ke V动脉期和门静脉期时,B组图像噪声均明显低于A组和C组(q分别=3.83、3.63,P均<0.05)。三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的肝、胰、腹主动脉(门静脉)CNR值比较,差异具有统计学意义(F分别=8.52、33.94、60.59、72.70、69.38、44.06;8.27、33.65、42.68、79.84、45.73、80.93;10.64、33.14、31.12、59.96、62.93、39.12,P均<0.05)。在40 ke V、50 ke V、60 ke V时,B组动脉期肝、胰、腹主动脉CNR值和门静脉期肝、胰、门静脉CNR值均明显高于A组和C组,差异均有统计学意义(q分别=16.73、8.72、12.71、10.82、14.65、15.71、11.67、12.51、8.77、10.52、9.79、13.80;8.79、12.83、10.62、14.62、10.81、8.51、10.66、12.79、13.72、9.81、10.53、12.49;4.49、5.64、6.82、10.53、7.52、5.93、11.61、9.27、6.31、10.65、9.51、10.11,P均<0.05)。三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像评分比较,差异均有统计学意义(F分别=42.58、77.97、18.30、25.04、4.25、5.14,P均<0.05)。两两比较结果显示,在40 ke V、50 ke V、60 ke V动脉期和门静脉期时,B组的图像评分最高,明显高于A组和C组(q分别=6.94、7.81、6.02、7.10;3.77、4.58、3.20、4.13;2.97、2.29、2.58、2.02,P均<0.05)。结论上腹部能谱CT智能匹配技术能够获得与常规CT平扫模式的对比剂用量,联合应用自适应统计迭代重组技术后,不仅能提高图像CNR以及降低对比剂用量,而且能提高图像质量。展开更多
Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method base...Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method based on multiple sinusoidal tapers and derive equations for multisource and multitrace conditions. Compared to conventional cross correlation and deconvolution reconstruction methods, the proposed method can more accurately reconstruct the relative amplitude of recordings. Multidomain iterative denoising improves the SNR of retrieved data. By analyzing the spectral characteristics of passive data before and after reconstruction, we found that the data are expressed more clearly after reconstruction and denoising. To compensate for the low-frequency information in active data using passive seismic data, we match the power spectrum, supplement it, and then smooth it in the frequency domain. Finally, we use numerical simulation to verify the proposed method and conduct prestack depth migration using data after low-frequency compensation. The proposed power-matching method adds the losing low frequency information in the active seismic data using the low-frequency information of passive- source seismic data. The imaging of compensated data gives a more detailed information of deep structures.展开更多
Methanol/TiO2（110） is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the vale...Methanol/TiO2（110） is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the valence band maximum of TiO2, preventing the hole transfer. To study the level alignment of this system, electronic structure of methanol covered TiO2（110） surface has been measured by ultraviolet photoelectron spectroscopy and the molecular orbitals of adsorbed methanol have been clearly identified. The results indicate the weak interaction between methanol and TiO2 substrate. The static electronic structure also suggests the mismatch of the energy levels. These static experiments have been performed without band gap excitation which is the prerequisite of a photocatalytie process. Future study of the transient electronic structure using time-resolved UPS has also been discussed.展开更多
文摘目的探究上腹部能谱CT智能匹配技术在提高图像对比噪声比(CNR)、降低对比剂使用量中的应用。方法选取行上腹部CT平扫以及双期增强扫描患者126例,分为实验组和对照组,各63例。实验组应用上腹部能谱CT智能匹配技术,对比剂含碘量为300 mg/kg,并采用滤波反投影法(FBP)获得A组图像;然后采用自适应统计迭代重组技术(AISR)获得B组图像。对照组采用常规CT平扫模式(120 k Vp),对比剂含碘量为450 mg/kg,采用FBP获得C组图像。比较三组图像在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像噪声以及肝、胰、门静脉、腹主动脉的CNR,并对三组图像进行评分。结果三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像噪声比较,差异均有统计学意义(F分别=187.72、246.35、51.98、127.50、23.15、48.96,P均<0.05)。两两比较结果显示,在40ke V动脉期和门静脉期,C组图像噪声低于B组和A组(q分别=8.32、9.37,P均<0.05);在50ke V动脉期和门静脉期时,B组和C组图像噪声均明显低于A组(q分别=5.73、6.84,P均<0.05);在60 ke V动脉期和门静脉期时,B组图像噪声均明显低于A组和C组(q分别=3.83、3.63,P均<0.05)。三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的肝、胰、腹主动脉(门静脉)CNR值比较,差异具有统计学意义(F分别=8.52、33.94、60.59、72.70、69.38、44.06;8.27、33.65、42.68、79.84、45.73、80.93;10.64、33.14、31.12、59.96、62.93、39.12,P均<0.05)。在40 ke V、50 ke V、60 ke V时,B组动脉期肝、胰、腹主动脉CNR值和门静脉期肝、胰、门静脉CNR值均明显高于A组和C组,差异均有统计学意义(q分别=16.73、8.72、12.71、10.82、14.65、15.71、11.67、12.51、8.77、10.52、9.79、13.80;8.79、12.83、10.62、14.62、10.81、8.51、10.66、12.79、13.72、9.81、10.53、12.49;4.49、5.64、6.82、10.53、7.52、5.93、11.61、9.27、6.31、10.65、9.51、10.11,P均<0.05)。三组在40 ke V、50 ke V、60 ke V动脉期和门静脉期的图像评分比较,差异均有统计学意义(F分别=42.58、77.97、18.30、25.04、4.25、5.14,P均<0.05)。两两比较结果显示,在40 ke V、50 ke V、60 ke V动脉期和门静脉期时,B组的图像评分最高,明显高于A组和C组(q分别=6.94、7.81、6.02、7.10;3.77、4.58、3.20、4.13;2.97、2.29、2.58、2.02,P均<0.05)。结论上腹部能谱CT智能匹配技术能够获得与常规CT平扫模式的对比剂用量,联合应用自适应统计迭代重组技术后,不仅能提高图像CNR以及降低对比剂用量,而且能提高图像质量。
基金sponsored by the Natural Science Foundation of China(No.41374115)National High Technology Research and Development Program of China(863 project)(No.2014AA06A605)
文摘Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method based on multiple sinusoidal tapers and derive equations for multisource and multitrace conditions. Compared to conventional cross correlation and deconvolution reconstruction methods, the proposed method can more accurately reconstruct the relative amplitude of recordings. Multidomain iterative denoising improves the SNR of retrieved data. By analyzing the spectral characteristics of passive data before and after reconstruction, we found that the data are expressed more clearly after reconstruction and denoising. To compensate for the low-frequency information in active data using passive seismic data, we match the power spectrum, supplement it, and then smooth it in the frequency domain. Finally, we use numerical simulation to verify the proposed method and conduct prestack depth migration using data after low-frequency compensation. The proposed power-matching method adds the losing low frequency information in the active seismic data using the low-frequency information of passive- source seismic data. The imaging of compensated data gives a more detailed information of deep structures.
文摘Methanol/TiO2（110） is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the valence band maximum of TiO2, preventing the hole transfer. To study the level alignment of this system, electronic structure of methanol covered TiO2（110） surface has been measured by ultraviolet photoelectron spectroscopy and the molecular orbitals of adsorbed methanol have been clearly identified. The results indicate the weak interaction between methanol and TiO2 substrate. The static electronic structure also suggests the mismatch of the energy levels. These static experiments have been performed without band gap excitation which is the prerequisite of a photocatalytie process. Future study of the transient electronic structure using time-resolved UPS has also been discussed.
