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磁共振指纹成像技术及其最新进展 被引量:7
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作者 李敏 董正超 +1 位作者 张学武 张秀明 《中国科学:生命科学》 CSCD 北大核心 2019年第1期28-40,共13页
磁共振指纹(magnetic resonance fingerprinting, MRF)技术是一种快速、多参数、定量化的磁共振成像新技术.该技术打破现有磁共振技术定性成像的局限性,在磁共振量化成像方式、提高抗噪性能、抗运动干扰性能方面获得了革命性的突破,并... 磁共振指纹(magnetic resonance fingerprinting, MRF)技术是一种快速、多参数、定量化的磁共振成像新技术.该技术打破现有磁共振技术定性成像的局限性,在磁共振量化成像方式、提高抗噪性能、抗运动干扰性能方面获得了革命性的突破,并使亚体素级的参数反演成为可能,是支撑精准医学研究的有效测量手段. MRF技术采用具有特殊时域变化特征的射频(radio frequency, RF)脉冲序列对成像对象进行时空域编码采样,产生由其组织生理参数和RF脉冲序列所决定的时空图像并由此获得空域信号的时间演化曲线(指纹);与此同时,利用Bloch方程与计算机仿真在相同的RF脉冲序列下,对组织所有可能产生的指纹信号进行计算机模拟,形成指纹库(字典).然后借助模式识别、数据挖掘等信息处理技术在字典中搜索与实测指纹信号相匹配的词条,从而索引到其对应的组织生理参数,实现量化成像.本文从成像机理、字典设计、重建算法等方面对MRF技术进行全面的阐述和分析,对MRF技术及其应用的最新进展进行评述,并对其未来的发展趋势提出预测与展望. 展开更多
关键词 磁共振成像 磁共振指纹 参数映射 激发脉冲 字典 模式识别
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Zeeman effects on d-wave superconductor and tunneling spectrum in normal-metal/d-wave superconductor tunnel junction
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作者 dong zhengchao 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2006年第5期597-605,共9页
We study the Zeeman effect on the d-wave superconductor and tunneling spectrum in normal-metal(N)/d-wave superconductor(S) junction by applying a Zeeman magnetic field to the S. It is shown that: (1) the Zeeman magnet... We study the Zeeman effect on the d-wave superconductor and tunneling spectrum in normal-metal(N)/d-wave superconductor(S) junction by applying a Zeeman magnetic field to the S. It is shown that: (1) the Zeeman magnetic field can lead to the S gap decreasing, and with the increase in Zeeman energy, the superconducting state is changed to the normal state, exhibiting a first-order phase transition; (2) the Zeeman magnetic field may make the zero-bias conductance peak split into two peaks, and the energy difference between the two splitting peaks in the conductance spectrum is equal to 2h0 (h0 is the Zeeman energy); (3) both the barrier strength of interface scattering and the temperature can lower the magnitudes of splitting peaks, of which the barrier strength can lead to the splitting peaks becoming sharp and the temperature can smear out the peaks, however, neither of them can influence the Zeeman effect. 展开更多
关键词 ZEEMAN effects D-WAVE SUPERCONDUCTOR tunneling SPECTRUM
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