Kelso Nathan, Lee Seung-Kyun, Bouchard Louis-S, Demas Vasiliki, Mück Michael, Pines Alexander, Clarke John
Department of Physics, University of California, Berkeley, CA 94720-7300, USA.
J Magn Reson. 2009 Oct;200(2):285-90. doi: 10.1016/j.jmr.2009.07.016. Epub 2009 Jul 18.
MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell's equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth's field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions.
磁共振成像（MRI）是一种用于临床诊断和材料表征的强大技术。图像是在均匀的静磁场中采集的，该静磁场比空间编码场梯度在视野范围内产生的场要高得多。如果没有这样的高场，由麦克斯韦方程组决定的场梯度的伴随分量会导致严重的畸变，使得传统MRI编码无法成像。在本文中，我们展示了用一种根本不同的方法获得的体模无畸变图像，其中施加的静磁场接近零。我们的技术涉及用均匀场和梯度场脉冲进行编码，并用超导量子干涉器件（SQUID）采集磁场信号。该方法可以扩展到弱环境场，有可能在不使用抵消线圈或屏蔽的情况下在地磁场中成像。其他潜在应用包括量子信息处理和长程铁磁相互作用的基础研究。
