高溫超導量子干涉元件於低磁場核磁共振及磁振造影之應用
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2008
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我們應用預先極化場的技術以及高溫超導量子干涉元件磁量計發展了一套低磁場核磁共振及磁振造影系統，其工作磁場強度為微特斯拉。磁共振系統的參數包括：預先極化場強度(Bp)、預先極化的時間(TBp)與預先極化後到脈衝場開啟的時間區間(Td)等都已最佳化。並於實驗中改變TBp與Td可以得到磁矩縱向的鬆弛時間。此外雷射光激發稀有氣體系統也已發展並整合於低磁場磁共振系統中，並分析其特性。而在水樣品的磁共振及磁振造影方面，為了改進我們的低磁場磁共振及磁振造影系統，我們使用的磁通轉換器並增強了預先極化場的強度以及提高了均勻場的均勻度。在101 T下得到線寬僅有0.9 Hz的磁共振光譜。我們也測量了三氟乙醇中，質子與氟原子間偶合的共振譜線。此外我們使用強度為24.6 T/m的梯度磁場，我們磁振造影系統的空間解析度可達到1毫米。
We applied prepolarization technology and high-Tc superconducting quantum interference device (SQUID) magnetometer to develop a Low-field NMR and MRI system in a microtesla magnetic field. The parameters to optimize the measurement of NMR detection were investigated. These parameters include the pre-polarization field, Bp, the pre-polarization time, TBp, and the delay time, Td, to turn on pulses after turning off the pre-polarization field. The decreasing of magnetization with the increasing Td of the applied pulse was analyzed to determine the longitudinal relaxation time. Otherwise, the optical pumping system was also developed and integrated in our low-field MRI system. The characteristics of hyperpolarized noble gas in our system had been investigated. For water NMR and MRI, we improved our high-Tc SQUID based low-field NMR and MRI system by using a flux transformer, increasing the strength of pre-polarization field and improving the homogeneity of the static field. The NMR spectrum with narrow linewidth in the order of 0.9 Hz at 101 uT in a single shot was obtained. We also detected the proton-fluorine couplings in trifluoroethanol. With a gradient field of 24.6 uT/m, we obtained a spatial resolution given by dz = 2*Pi*df/r*G = 1 mm in proton magnetic resonance imaging, where = 42.58 kHz/mT.
We applied prepolarization technology and high-Tc superconducting quantum interference device (SQUID) magnetometer to develop a Low-field NMR and MRI system in a microtesla magnetic field. The parameters to optimize the measurement of NMR detection were investigated. These parameters include the pre-polarization field, Bp, the pre-polarization time, TBp, and the delay time, Td, to turn on pulses after turning off the pre-polarization field. The decreasing of magnetization with the increasing Td of the applied pulse was analyzed to determine the longitudinal relaxation time. Otherwise, the optical pumping system was also developed and integrated in our low-field MRI system. The characteristics of hyperpolarized noble gas in our system had been investigated. For water NMR and MRI, we improved our high-Tc SQUID based low-field NMR and MRI system by using a flux transformer, increasing the strength of pre-polarization field and improving the homogeneity of the static field. The NMR spectrum with narrow linewidth in the order of 0.9 Hz at 101 uT in a single shot was obtained. We also detected the proton-fluorine couplings in trifluoroethanol. With a gradient field of 24.6 uT/m, we obtained a spatial resolution given by dz = 2*Pi*df/r*G = 1 mm in proton magnetic resonance imaging, where = 42.58 kHz/mT.
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超導量子干涉元件, 核磁共振, 磁振造影, SQUID, NMR, MRI