In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contr...In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contributions of cardiac equivalent source models and volume conductor models to the MCG are deeply and comprehensively investigated. The single dipole source model, the multiple dipoles source model and the equivalent double layer （EDL） source model are analysed and compared with the cardiac equivalent source models. Meanwhile, the effect of the volume conductor model on the MCG combined with these cardiac equivalent sources is investigated. The simulation results demonstrate that the cardiac electrophysiological information will be partly missed when only the single dipole source is taken, while the EDL source is a good option for MCG simulation and the effect of the volume conductor is smallest for the EDL source. Therefore, the EDL source is suitable for the study of MCG forward and inverse problems, and more attention should be paid to it in future MCG studies.展开更多
The paper presents a morphological study of real time magnetocardiograms(MCGs) of a normal subject.The MCGs were measured by using a 3 D second order gradiometer connected to three rf SQUIDs in a prefabricated magneti...The paper presents a morphological study of real time magnetocardiograms(MCGs) of a normal subject.The MCGs were measured by using a 3 D second order gradiometer connected to three rf SQUIDs in a prefabricated magnetically shielded room.The base line of the detecting coil for Bz is 2.8 cm and that of the coil for Bx and By is 1.4 cm.The magnetic field components perpendicular to the chest (Bz component )and tangential to the chest (Bx,By components) were studied.From isofield contour maps and arrow maps of the QRS wave of the MCG,when multiple sources exist simulataneously,we can infer the locations and positions of different sources by combining the Bz component with the Bx and By components.The analyzed results showed that a method using a 3 D second order gradiometer that we developed is useful for discriminating the directions and locations of multiple sources.展开更多
针对心磁信号工频及背景噪声干扰问题,提出了广义S变换奇异值分解(singular value decomposition,SVD)滤波方法.在离散S变换基础上,导出了广义矩阵S变换和逆变换公式.通过对采样信号进行广义S变换,调节时频分辨率,利用SVD分解方法确定...针对心磁信号工频及背景噪声干扰问题,提出了广义S变换奇异值分解(singular value decomposition,SVD)滤波方法.在离散S变换基础上,导出了广义矩阵S变换和逆变换公式.通过对采样信号进行广义S变换,调节时频分辨率,利用SVD分解方法确定有效心磁信号区域,实现自适应时频滤波.实验结果表明,该方法能有效滤除工频及背景噪声干扰,且在较少奇异值个数情况下可获得更好的滤波性能.展开更多
A single-channel high-Tc dc-SQUID magnetometer and gradiometer have been developed to record the magnetic field component perpendicular to the human chest generated by heart-beat. Magnetocardiogram (MCG) measurements ...A single-channel high-Tc dc-SQUID magnetometer and gradiometer have been developed to record the magnetic field component perpendicular to the human chest generated by heart-beat. Magnetocardiogram (MCG) measurements have been carried out inside a magnetically shielded room. By sequentially adjusting a non-magnetic patient table with 5 cm pitch in X and Y directions, the field signals on a rectangle grid 5×5 over the chest area were registered in real time trace point by point with a typical dwell time over 30 cardiocycles each. Utilizing standard electrocardiogram (ECG) recordings as timing reference measured simultaneously with the MCG signals, the MCG data were then averaged and combined to form magnetic field patterns every 10 ms or so. Both the current dipole, which is parallel to MCG measuring plane and produces the vertical magnetic field, and its depth were determined as a function of time in a standard way. We have compared the MCG of healthy hearts with that of a heart with right bundle展开更多
A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO3 bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO2/YSZ multilayer on ?50...A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO3 bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO2/YSZ multilayer on ?50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm?1Hz?1/2 in the white region and 596 fT.cm?1Hz?1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.展开更多
采用矩阵奇异值分解(singular value decomposition,SVD)的方法,对高温射频超导量子干涉仪(HTc rf-SQUID)采集到的单通道心磁信号进行处理.证明了对于近似周期性的心磁信号,在无参考噪声的情况下矩阵奇异值分解的方法与自适应窄带陷波...采用矩阵奇异值分解(singular value decomposition,SVD)的方法,对高温射频超导量子干涉仪(HTc rf-SQUID)采集到的单通道心磁信号进行处理.证明了对于近似周期性的心磁信号,在无参考噪声的情况下矩阵奇异值分解的方法与自适应窄带陷波相结合有较好的消除广谱噪声的效果.展开更多
基金supported by the State Key Development Program for Basic Research of China (Grant Nos. 2007CB512100 and2006CB601007)the National Natural Science Foundation of China (Grant No. 10674006)+2 种基金the National High Technology Research and Development Program of China (Grant No. 2007AA03Z238)China Postdoctoral Science Foundation (Grant No. 20090461376)the Fundamental Research Funds for the Central Universities (Grant No. KYJD09001)
文摘In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contributions of cardiac equivalent source models and volume conductor models to the MCG are deeply and comprehensively investigated. The single dipole source model, the multiple dipoles source model and the equivalent double layer （EDL） source model are analysed and compared with the cardiac equivalent source models. Meanwhile, the effect of the volume conductor model on the MCG combined with these cardiac equivalent sources is investigated. The simulation results demonstrate that the cardiac electrophysiological information will be partly missed when only the single dipole source is taken, while the EDL source is a good option for MCG simulation and the effect of the volume conductor is smallest for the EDL source. Therefore, the EDL source is suitable for the study of MCG forward and inverse problems, and more attention should be paid to it in future MCG studies.
文摘The paper presents a morphological study of real time magnetocardiograms(MCGs) of a normal subject.The MCGs were measured by using a 3 D second order gradiometer connected to three rf SQUIDs in a prefabricated magnetically shielded room.The base line of the detecting coil for Bz is 2.8 cm and that of the coil for Bx and By is 1.4 cm.The magnetic field components perpendicular to the chest (Bz component )and tangential to the chest (Bx,By components) were studied.From isofield contour maps and arrow maps of the QRS wave of the MCG,when multiple sources exist simulataneously,we can infer the locations and positions of different sources by combining the Bz component with the Bx and By components.The analyzed results showed that a method using a 3 D second order gradiometer that we developed is useful for discriminating the directions and locations of multiple sources.
文摘针对心磁信号工频及背景噪声干扰问题,提出了广义S变换奇异值分解(singular value decomposition,SVD)滤波方法.在离散S变换基础上,导出了广义矩阵S变换和逆变换公式.通过对采样信号进行广义S变换,调节时频分辨率,利用SVD分解方法确定有效心磁信号区域,实现自适应时频滤波.实验结果表明,该方法能有效滤除工频及背景噪声干扰,且在较少奇异值个数情况下可获得更好的滤波性能.
基金the National Center for R&D on Superconductivity, Chinese Academy of Sciences (Grant No. KJCX2-W4)the Ministry of Science and Technology of China (Grant No. G19990646).
文摘A single-channel high-Tc dc-SQUID magnetometer and gradiometer have been developed to record the magnetic field component perpendicular to the human chest generated by heart-beat. Magnetocardiogram (MCG) measurements have been carried out inside a magnetically shielded room. By sequentially adjusting a non-magnetic patient table with 5 cm pitch in X and Y directions, the field signals on a rectangle grid 5×5 over the chest area were registered in real time trace point by point with a typical dwell time over 30 cardiocycles each. Utilizing standard electrocardiogram (ECG) recordings as timing reference measured simultaneously with the MCG signals, the MCG data were then averaged and combined to form magnetic field patterns every 10 ms or so. Both the current dipole, which is parallel to MCG measuring plane and produces the vertical magnetic field, and its depth were determined as a function of time in a standard way. We have compared the MCG of healthy hearts with that of a heart with right bundle
文摘A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO3 bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO2/YSZ multilayer on ?50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm?1Hz?1/2 in the white region and 596 fT.cm?1Hz?1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.
文摘采用矩阵奇异值分解(singular value decomposition,SVD)的方法,对高温射频超导量子干涉仪(HTc rf-SQUID)采集到的单通道心磁信号进行处理.证明了对于近似周期性的心磁信号,在无参考噪声的情况下矩阵奇异值分解的方法与自适应窄带陷波相结合有较好的消除广谱噪声的效果.
