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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Microtesla MRI with a superconducting quantum interference device.
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Microtesla MRI with a superconducting quantum interference device.

机译：具有超导量子干涉装置的Microtesla MRI。

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MRI scanners enable fast, noninvasive, and high-resolution imaging of organs and soft tissue. The images are reconstructed from NMR signals generated by nuclear spins that precess in a static magnetic field B(0) in the presence of magnetic field gradients. Most clinical MRI scanners operate at a magnetic field B(0) = 1.5 T, corresponding to a proton resonance frequency of 64 MHz. Because these systems rely on large superconducting magnets, they are costly and demanding of infrastructure. On the other hand, low-field imagers have the potential to be less expensive, less confining, and more mobile. The major obstacle is the intrinsically low sensitivity of the low-field NMR experiment. Here, we show that prepolarization of the nuclear spins and detection with a superconducting quantum interference device (SQUID) yield a signal that is independent of B(0), allowing acquisition of high-resolution MRIs in microtesla fields. Reduction of the strength of the measurement field eliminates inhomogeneous broadening of the NMR lines, resulting in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present high-resolution images of phantoms and other samples and T(1)-weighted contrast images acquired in highly inhomogeneous magnetic fields of 132 microT; here, T(1) is the spin-lattice relaxation time. These techniques could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.
机译：MRI扫描仪可对器官和软组织进行快速，无创和高分辨率成像。从核自旋产生的NMR信号重构图像，核磁共振自旋在存在磁场梯度的情况下在静态磁场B（0）中进动。大多数临床MRI扫描仪在磁场B（0）= 1.5 T下运行，对应于64 MHz的质子共振频率。因为这些系统依赖于大型超导磁体，所以它们昂贵且对基础设施的要求很高。另一方面，低场成像仪可能会变得更便宜，更局限，移动性更强。主要障碍是低场NMR实验的固有低灵敏度。在这里，我们显示核自旋的预极化和超导量子干涉装置（SQUID）的检测产生的信号独立于B（0），从而允许在微特斯拉场中获取高分辨率MRI。测量场强度的减小消除了NMR线的不均匀加宽，从而提高了用于编码图像的磁场梯度的固定强度的信噪比和空间分辨率。我们提出了幻影和其他样品的高分辨率图像，以及在132 microT的高度不均匀磁场中获得的T（1）加权对比图像；在此，T（1）是自旋晶格弛豫时间。这些技术可以很容易地适应现有的用于脑信号的磁源成像的多通道SQUID系统。进一步的潜在应用包括用于肿瘤筛查和对身体周围区域成像的低成本系统。

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