The use of very low noise magnetometers based on Superconducting QUantum Interference Devices (SQUIDs) enables nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) in microtesla magnetic fields. An untuned superconducting flux transformer coupled to a SQUID achieves a magnetic field noise of 10(-15) T Hz(-1/2). The frequency-independent response of this magnetometer combined with prepolarization of the nuclear spins yields an NMR signal that is independent of the Larmor frequency omega0. An MRI system operating in a field of 132 microT, corresponding to a proton frequency of 5.6 kHz, achieves an in-plane resolution of 0.7 x 0.7 mm2 in phantoms. Measurements of the longitudinal relaxation time T1 in different concentrations of agarose gel over five decades of frequency reveal much greater T1-differentiation at fields below a few millitesla. Microtesla MRI has the potential to image tumors with substantially greater T1-weighted contrast than is achievable in high fields in the absence of a contrast agent.

中文翻译：

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在微特斯拉场中进行SQUID检测的磁共振成像。

基于超导量子干扰设备（SQUID）的超低噪声磁力计的使用可在微特斯拉磁场中实现核磁共振（NMR）和磁共振成像（MRI）。与SQUID耦合的未调谐超导通量互感器实现10（-15）T Hz（-1/2）的磁场噪声。该磁力计的频率独立响应与核自旋的预极化相结合，产生的NMR信号与拉莫尔频率omega0不相关。在132 microT的磁场中运行的MRI系统（对应于5.6 kHz的质子频率）在幻像中实现了0.7 x 0.7 mm2的面内分辨率。在数十年的频率上，不同浓度的琼脂糖凝胶的纵向弛豫时间T1的测量结果显示，在低于几毫特斯拉的磁场中，T1的分化程度更高。与没有造影剂的高视野相比，Microtesla MRI可以对肿瘤成像，其T1加权对比度明显更高。