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在简易磁屏蔽室中,用单通道的高温超导rf SQUID梯度计构成心磁图(MCG)测量系统,依照MCG测定部位的约定,测得数例成人胸前多点MCG.不计心动周期随时问的变化,用数据分析软件对这些MCG数据进行分析处理,得到包括了空间信息、可直观展示心脏电磁活动的二维心磁图谱(例如等磁图、时序等磁图、电流箭头图和时序电流箭头图等) 相似文献
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随着环境污染的加重,具有高梯度磁场的高温超导磁分离系统作为一种新型高效便捷的污水处理系统得到发展和应用.本文主要介绍了制冷机传导冷却高温超导磁体的便于装卸杜瓦的设计,利用ANSYS软件分析了杜瓦的应力和形变,分析了漏热、温度分布和对磁体的冷却情况,使高温超导磁体在磁分离系统中满足要求并保持正常运行. 相似文献
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针对传统超导磁梯度张量探头中多个磁梯度计间的噪声互扰会降低系统灵敏度的问题,本文提出了一种基于二维傅里叶变换的磁梯度张量探头结构优化方法。通过二维傅里叶变换及逆变换将磁场矢量Z分量沿着Z轴方向的二阶空间导数Bzzz转换为磁场矢量的3个分量以及一阶磁梯度张量的5个独立元素,把通常至少需要6个SQUID一阶平面磁梯度计的探头结构简化为只需要1个二阶SQUID磁梯度计的探头结构,消除了磁梯度计之间的噪声干扰,系统灵敏度提高了1个数量级。实验结果表明该探头具有良好的探测能力,证明了这种优化方法的可行性。 相似文献
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本文研究了一种自建的低成本简易磁屏蔽室及其操控条件,提出了能被高温超导rf SQUID仪器所接受的简易磁屏蔽室,并且运用由该磁屏蔽室和rf SQUID梯度计所构成的组合系统测量了微弱的生物磁信号.研究结果表明,该磁屏蔽室能够有效降低电磁干扰,确保SQUID长时稳定工作,基于该磁屏蔽室的复合MCG测量系统具备捕捉微弱生物磁信号的能力,且所得信号具有可接受的信噪比.这将使得开发一种低造价的实用高温超导MCG测量系统成为现实. 相似文献
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SQUID gradiometer techniques are widely used in noise cancellation for biomagnetic measurements.An appropriate gradiometer baseline is very important for the biomagnetic detection with high performance.By placing several magnetometers at different heights along the vertical direction,we could simultaneously obtain the synthetic gradiometers with different baselines.By using the traditional signal-to-noise ratio(SNR) as a performance index,we successfully obtain an optimal baseline for the magnetocardiography(MCG) measurement in a magnetically shielded room(MSR).Finally,we obtain an optimal baseline of 7 cm and use it for the practical MCG measurement in our MSR.The SNR about 38 dB is obtained in the recorded MCG signal. 相似文献
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Simulation study of a magnetocardiogram based on a virtual heart model: effect of a cardiac equivalent source and a volume conductor
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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. 相似文献
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心脏磁场源重构, 即通过人体胸腔表面的磁场阵列测量信号反演产生该磁场的电流源分布, 是一种无创地研究心脏电活动的方法. 本文用线性化方程描述测量磁场与心脏内部电流源的关系, 并通过一种贪婪优化的方法得到了源重构的稀疏解. 通过近似正交化过程和改变迭代算法中原子的选择方式, 降低了优化算法的复杂度, 可在保证源重构精度的情况下, 快速搜索源空间中强度比较大的位置. 文中通过一组正常人的心磁测量数据, 说明了源重构方法的有效性. 这组数据的研究结果表明, 强度大于65%的重构电流源的空间移动轨迹与心脏除极和复极电活动的传导过程基本符合. 其QRS 和ST-T 段的实测心磁图与重构电流源产生的磁场图的平均拟合优度分别为99.36%和99.78%.
关键词:
心磁图
逆问题
稀疏解
正交匹配追踪 相似文献
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Singular value decomposition with normalized period for magnetocaridiography signal processing
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In this paper, we have developed an algorithm based on singular value
decomposition (SVD) for matrix. And the novel SVD algorithm with normalized
period of cardiac cycles is presented. The results from real
magnetocardiography (MCG) data processing show that the new algorithm is
better than the standard one not only in suppressing noises, but also in
providing high-fidelity MCG signals. 相似文献
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Microbubbles containing gadolinium as contrast agents for both phase contrast and magnetic resonance imaging
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Rongbiao Tang Fuhua Yan Guo-Yuan Yang Ke-Min Chen 《Journal of synchrotron radiation》2018,25(2):560-564
Portal vein imaging is an important method for investigating portal venous disorders. However, the diagnostic requirements are not usually satisfied when using single imaging techniques. Diagnostic accuracy can be improved by combining different imaging techniques. Contrast agents that can be used for combined imaging modalities are needed. In this study, the feasibility of using microbubbles containing gadolinium (MCG) as contrast agents for both phase contrast imaging (PCI) and magnetic resonance imaging (MRI) are investigated. MCG were made by encapsulating sulfur hexafluoride (SF6) gas with gadolinium and lyophilized powder. Absorption contrast imaging (ACI) and PCI of MCG were performed and compared in vitro. MCG were injected into the main portal trunk of living rats. PCI and MRI were performed at 2 min and 10 min after MCG injection, respectively. PCI exploited the differences in the refractive index and visibly showed the MCG, which were not detectable by ACI. PCI could facilitate clear revelation of the MCG‐infused portal veins. The diameter of the portal veins could be determined by the largest MCG in the same portal vein. The minimum diameter of clearly detected portal veins was about 300 µm by MRI. These results indicate that MCG could enhance both PCI and MRI for imaging portal veins. The detection sensitivity of PCI and MRI could compensate for each other when using MCG contrast agents for animals. 相似文献
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显微红外光谱分析技术是将红外光谱仪和显微镜结合发展而来的分析技术。该技术样品处理简单,可用于微区分析和微量分析,并且能反映样品的本质特征。人参包括林下山参、园参和野山参,而我国禁止采挖野山参。因此,药典只收录了林下山参和园参。该工作使用显微红外光谱技术,结合判别分析建立了对林下山参和园参的无损识别模型。收集了20个林下山参和24个园参后,采集了其显微红外光谱。其中,33个样品被随机划分为校正集,11个为验证集。建立模型时,优化了预处理方法、主成分数、建模波段和扫描部位。最后,使用多元散射校正+Savitzky-Golay平滑的预处理方法、3932.14~669.18 cm-1的波段、4个主成分数和芦头部位建立了最优的判别分析模型,准确率达到100%。结果表明,结合判别分析的显微红外光谱技术,样品处理简单、快速、无损、有效,可用于林下山参和园参的无损识别。 相似文献
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Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUIDs).As a room-temperature magnetic-field sensor,optically pumped magnetometer(OPM)has shown to have comparable sensitivity to that of SQUIDs,which is very suitable for biomagnetic measurements.In this paper,a synthetic gradiometer was constructed by using two OPMs under spin-exchange relaxation-free(SERF)conditions within a moderate magnetically shielded room(MSR).The magnetic noise of the OPM was measured to less than 70 fT/Hz1/2.Under a baseline of 100 mm,noise cancellation of about 30 dB was achieved.MCG was successfully measured with a signal to noise ratio(SNR)of about 37 dB.The synthetic gradiometer technique was very effective to suppress the residual environmental fields,demonstrating the OPM gradiometer technique for highly cost-effective biomagnetic measurements. 相似文献
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We present a new filter scheme for magnetocardiogram (MCG) signal processing based on the quasi-periodic characteristic of the signals. The key points of this scheme are to determine the exact numbers of data points in each cardiac cycle by using electrocardiogram (ECG) data acquired simultaneously with the MCG signal and to normalize the MCG data sequence in each cycle into an identical length. Compared with conventional filters, the scheme has the advantage of more powerful noise suppression with less signal distortion. The desire for having high quality output signals from raw MCG data acquired in a simple shielded room or even in unshielded environment may be realized with the scheme. 相似文献
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Considering the properties of slow change and quasi-periodicity of
magnetocardiography (MCG) signal, we use an integrated technique of adaptive
and low-pass filtering in dealing with two-channel MCG data measured by high
$T_{\rm c}$ SQUIDs. The adaptive filter in the time domain is based on a noise feedback
normalized least-mean-square (NLMS) algorithm, and the low-pass filter with
a cutoff at 100Hz in the frequency domain characterized by Gaussian functions is
combined with a notch at the power line frequency. In this way, both
relevant and irrelevant noises in original MCG data are largely eliminated.
The method may also be useful for other slowly varying quasi-periodical
signals. 相似文献