ULF MRI为MEG和NCI提供的超灵敏SQUID仪器
Ultra-sensitive SQUID instrumentation for MEG and NCI by ULF MRI
摘要：
介绍了生物磁学中对超灵敏SQUID仪器的结构要求。通常，SQUID感应耦合到拾取线圈，并且对于这种布置，可以通过增加感测线圈面积来改善噪声性能。为了达到最佳的灵敏度，必须考虑信噪比（SNR），这是一个复杂的源特性和噪声源之间的相互作用。事实证明，即使对于相同的源，也需要单独的拾波线圈设计来获得各种噪声特性。因此，具有不同尺寸拾波线圈的混合系统是多用途应用的最佳选择。还描述了一个接近SQUID本征噪声水平的单通道系统。这可以通过利用特殊的杜瓦瓶设计来实现，从而进一步提高SNR。这样的系统可以用于通过超低场磁共振的电流密度成像和神经元电流成像，其中它还必须能够耐受高达100-200 mT的场。
英文摘要：
The requirements for the construction of ultra-sensitive SQUID instrumentation as used in biomagnetism are presented. Typically, SQUIDs are inductively coupled to pick-up coils and for this arrangement one can improve the noise performance by increasing the sensing coil area. To achieve optimum sensitivity one has to consider the signal-to-noise ratio (SNR), which is an intricate interplay between source characteristics and noise origin. It turns out that separate pick-up coil designs are needed for various noise characteristics even for an identical source. Hence, a hybrid system with differently sized pick-up coils presents the best option for multipurpose applications. A single channel system with close to SQUID intrinsic noise level is also described. This is possible by utilizing a special dewar design and thereby enabling a further increase in SNR. Such a system might be used for current density imaging and neuronal current imaging by ultra-low-field magnetic resonance where it also must be able to be field-tolerant to up to 100-200 mT.
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