A SIGNAL-TO-NOISE CALIBRATION PROCEDURE FOR NMR IMAGING-SYSTEMS
A SIGNAL-TO-NOISE CALIBRATION PROCEDURE FOR NMR IMAGING-SYSTEMS
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DOI：
10.1118/1.595484
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发表时间：
1984-01-01
期刊：
影响因子：
3.8
通讯作者：
PFEIFER, LM
中科院分区：
文献类型：
--
作者：
EDELSTEIN, WA;BOTTOMLEY, PA;PFEIFER, LM
提出了一种基于蒸馏水在圆柱瓶中的核磁共振投影的核磁共振成像系统信噪比校准技术。这种测量可以将任何磁场中的RF线圈的任何布置表征为每毫升乘以根赫兹的信号噪声比。典型患者的电感损耗必须包括在校准中，这种损耗可以在特定系统中通过适用于该系统的外接电阻器(S)来模拟。或者，提出了一种射频感应阻尼体模，该体模由导线的导电回路组成，其中含有适当的电阻，该电阻可以插入任何核磁共振成像线圈中来模拟受试者的Q衰减。可以使用相同的电阻，而与线圈结构的细节无关。此外，如果用串联电容器在每个频率调谐环路电感，那么对于所有频率，相同的环路电阻将作为人体受试者阻尼的良好近似值。这种“投影法”信噪比与从洛伦兹型谱线测量的传统信噪比有关，ψP=ψL[2/T2]1/2，其中ψ代表信噪比，下标Pand L分别代表投影法和“洛伦兹法”，T2是洛伦兹法中使用的谱线的横向弛豫时间。
A nuclear magnetic resonance (NMR) imaging system signal‐to‐noise calibration technique based on an NMR projection of distilled water in a cylindrical bottle is proposed. This measurement can characterize any arrangement of rf coils in any magnetic field as signal to noise per ml times root Hz. Inductive losses in a typical patient must be included in the calibration, and such losses can be simulated in a particular system by an externally attached resistor(s) appropriate to that system. Alternatively, an rf inductive damping phantom consisting of a conducting loop of wire containing an appropriate resistor is suggested that can be inserted into any NMR imaging coil to simulate subjectQdamping. The same resistor can be used, independent of the details of the coil construction. Furthermore, if the loop inductance is tuned out at each frequency with a series capacitor, then the same loop resistance will serve for all frequencies as a good approximation to human subject damping. This “projection method” signal‐to‐noise ratio is related to the conventional signal‐to‐noise ratio measured from a Lorentzian‐shaped spectral line as ψP=ψL[2/T2]1/2, where ψ stands for signal‐to‐noise ratio, subscriptsPandLstand, respectively, for the projection and “Lorentzian” methods, andT2is the transverse relaxation time of the spectral line used in the Lorentzian method.