Conventional multiple breath-hold two-dimensional （2D） balanced steady-state free precession （SSFP） presents many difficulties in cardiac cine magnetic resonance imaging （MRI）. Recently, a self-gated free-breath...Conventional multiple breath-hold two-dimensional （2D） balanced steady-state free precession （SSFP） presents many difficulties in cardiac cine magnetic resonance imaging （MRI）. Recently, a self-gated free-breathing three-dimensional （3D） SSFP technique has been proposed as an alternative in many studies. However, the accuracy and effectiveness of selfgating signals have been barely studied before. Since self-gating signals are crucially important in image reconstruction, a systematic study of self-gating signals and comparison with external monitored signals are needed. Previously developed self-gated free-breathing 3D SSFP techniques are used on twenty-eight healthy volunteers. Both electrocardiographic （ECG） and respiratory bellow signals are also acquired during the scan as external signals. Self-gating signal and external signal are compared by trigger and gating window. Gating window is proposed to evaluate the accuracy and effectiveness of respiratory self-gating signal. Relative deviation of the trigger and root-mean-square-deviation of the cycle duration are calculated. A two-tailed paired t-test is used to identify the difference between self-gating and external signals. A Wilcoxon signed rank test is used to identify the difference between peak and valley self-gating triggers. The results demonstrate an excellent correlation （P = 0, R 〉 0.99） between self-gating and external triggers. Wilcoxon signed rank test shows that there is no significant difference between peak and valley self-gating triggers for both cardiac （H = 0, P 〉 0.10） and respiratory （H = 0, P 〉 0.44） motions. The difference between self-gating and externally monitored signals is not significant （two-tailed paired-sample t-test： H = 0, P 〉 0.90）. The self-gating signals could demonstrate cardiac and respiratory motion accurately and effectively as ECG and respiratory bellow. The difference between the two methods is not significant and can be explained. Furthermore, few ECG trigger errors appear in some subjects while these errors are not found in self-gating signals.展开更多
Semiconductor electrocatalysis with weak conductivity can accumulate extremely high carriers at semiconductor-electrolyte interface by self-gating effect,which strongly promotes electrocatalytic efficiency.The correla...Semiconductor electrocatalysis with weak conductivity can accumulate extremely high carriers at semiconductor-electrolyte interface by self-gating effect,which strongly promotes electrocatalytic efficiency.The correlation between semiconductor carrier mobility and electrocatalysis performance is still unclear.Herein atomic-thin transition metal dichalcogenides based composites have been developed for hydrogen evolution reaction(HER)performed with on-chip microdevices.Electrical and electrochemical measurement of individual flack verified the key role of high carrier mobility for enhanced HER activity.Carrier mobility regulation further demonstrated its high dependence with HER performance under self-gating.Our study provides new insight into the carrier mobility of the semiconductor in the electrocatalysis,paving the way for designing high-performance semiconductor catalysts.展开更多
This paper presents a nonlinear profile order scheme for three-dimensional（3D） hybrid radial acquisition applied to self-gated, free-breathing cardiac cine magnetic resonance imaging（MRI）. In self-gated, free-brea...This paper presents a nonlinear profile order scheme for three-dimensional（3D） hybrid radial acquisition applied to self-gated, free-breathing cardiac cine magnetic resonance imaging（MRI）. In self-gated, free-breathing cardiac cine MRI,respiratory and cardiac motions are unpredictable during acquisition, especially for retrospective reconstruction. Therefore,the non-uniformity of the k-space distribution is an issue of great concern during retrospective self-gated reconstruction. A nonlinear profile order with varying azimuthal increments was provided and compared with the existing golden ratio-based profile order. Optimal parameter values for the nonlinear formula were chosen based on simulations. The two profile orders were compared in terms of the k-space distribution and phantom and human image results. An approximately uniform distribution was obtained based on the nonlinear profile order for persons with various heart rates and breathing patterns.The nonlinear profile order provides more stable profile distributions and fewer streaking artifacts in phantom images. In a comparison of human cardiac cine images, the nonlinear profile order provided results comparable to those provided by the golden ratio-based profile order, and the images were suitable for diagnosis. In conclusion, the nonlinear profile order scheme was demonstrated to be insensitive to various motion patterns and more useful for retrospective reconstruction.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.81501463,61471349,81671853,81571669,and 61671026)the National High Technology Research and Development Program of China(Grant No.2015AA043203)+5 种基金the Natural Science Foundation of Beijing,China(Grant No.7162112)Guangdong Innovative Research Team Program of China(Grant No.2011S013)the Natural Science Foundation of Guangdong Province,China(Grant Nos.2014A030310360 and 2014A0202015028)the Beijing Center for Mathematics and Information Interdisciplinary Sciences,Shenzhen Fundamental Research Program,China(Grant Nos.JCYJ201500731154850923 and JCYJ20140417113430665)Shenzhen High-level Oversea Talent Program,China(Grant No.KQJSCX20160301144248)the Nanshan Technology Research Fund,China(Grant No.KC2014JSQN0001A)
文摘Conventional multiple breath-hold two-dimensional （2D） balanced steady-state free precession （SSFP） presents many difficulties in cardiac cine magnetic resonance imaging （MRI）. Recently, a self-gated free-breathing three-dimensional （3D） SSFP technique has been proposed as an alternative in many studies. However, the accuracy and effectiveness of selfgating signals have been barely studied before. Since self-gating signals are crucially important in image reconstruction, a systematic study of self-gating signals and comparison with external monitored signals are needed. Previously developed self-gated free-breathing 3D SSFP techniques are used on twenty-eight healthy volunteers. Both electrocardiographic （ECG） and respiratory bellow signals are also acquired during the scan as external signals. Self-gating signal and external signal are compared by trigger and gating window. Gating window is proposed to evaluate the accuracy and effectiveness of respiratory self-gating signal. Relative deviation of the trigger and root-mean-square-deviation of the cycle duration are calculated. A two-tailed paired t-test is used to identify the difference between self-gating and external signals. A Wilcoxon signed rank test is used to identify the difference between peak and valley self-gating triggers. The results demonstrate an excellent correlation （P = 0, R 〉 0.99） between self-gating and external triggers. Wilcoxon signed rank test shows that there is no significant difference between peak and valley self-gating triggers for both cardiac （H = 0, P 〉 0.10） and respiratory （H = 0, P 〉 0.44） motions. The difference between self-gating and externally monitored signals is not significant （two-tailed paired-sample t-test： H = 0, P 〉 0.90）. The self-gating signals could demonstrate cardiac and respiratory motion accurately and effectively as ECG and respiratory bellow. The difference between the two methods is not significant and can be explained. Furthermore, few ECG trigger errors appear in some subjects while these errors are not found in self-gating signals.
基金the National Natural Science Foundation of China(No.22175060,21975067)the National Basic Research Programs of China(No.2016YFA0300901)+4 种基金the National Science Foundation of China(No.11974105)the support from the U.S.National Science Foundation CREST Program(NSF No.HRD-1547723)the National Natural Science Foundation of China(No.51902346)Natural Science Foundation of China(No.21805077)the Natural Science Foundation of Hunan Province(No.2019JJ50075)。
文摘Semiconductor electrocatalysis with weak conductivity can accumulate extremely high carriers at semiconductor-electrolyte interface by self-gating effect,which strongly promotes electrocatalytic efficiency.The correlation between semiconductor carrier mobility and electrocatalysis performance is still unclear.Herein atomic-thin transition metal dichalcogenides based composites have been developed for hydrogen evolution reaction(HER)performed with on-chip microdevices.Electrical and electrochemical measurement of individual flack verified the key role of high carrier mobility for enhanced HER activity.Carrier mobility regulation further demonstrated its high dependence with HER performance under self-gating.Our study provides new insight into the carrier mobility of the semiconductor in the electrocatalysis,paving the way for designing high-performance semiconductor catalysts.
基金supported by the National Natural Science Foundation of China(Grant Nos.81501463,61671026,81571669,and 81671853)the Natural Science Foundation of Guangdong Province,China(Grant No.2014A030310360)+3 种基金Guangdong Innovative Research Team Program of China(Grant No.2011S013)the Basic Research Project of Shenzhen City,China(Grant Nos.JCYJ20140417113430639 and JCYJ20160429172357751)the High-level Oversea Talent Program of Shenzhen City,China(Grant No.KQJSCX20160301144248)Beijing Center for Mathematics and Information Interdisciplinary Sciences of China
文摘This paper presents a nonlinear profile order scheme for three-dimensional（3D） hybrid radial acquisition applied to self-gated, free-breathing cardiac cine magnetic resonance imaging（MRI）. In self-gated, free-breathing cardiac cine MRI,respiratory and cardiac motions are unpredictable during acquisition, especially for retrospective reconstruction. Therefore,the non-uniformity of the k-space distribution is an issue of great concern during retrospective self-gated reconstruction. A nonlinear profile order with varying azimuthal increments was provided and compared with the existing golden ratio-based profile order. Optimal parameter values for the nonlinear formula were chosen based on simulations. The two profile orders were compared in terms of the k-space distribution and phantom and human image results. An approximately uniform distribution was obtained based on the nonlinear profile order for persons with various heart rates and breathing patterns.The nonlinear profile order provides more stable profile distributions and fewer streaking artifacts in phantom images. In a comparison of human cardiac cine images, the nonlinear profile order provided results comparable to those provided by the golden ratio-based profile order, and the images were suitable for diagnosis. In conclusion, the nonlinear profile order scheme was demonstrated to be insensitive to various motion patterns and more useful for retrospective reconstruction.
