@article {331, title = {Microtesla MRI with a superconducting quantum interference device}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {101}, year = {2004}, note = {P Natl Acad Sci USA823ZCTimes Cited:76Cited References Count:29}, month = {May 25}, pages = {7857-7861}, abstract = {

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 muT; here, T, 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.

}, keywords = {system}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0402382101}, url = {://WOS:000221652000005}, author = {McDermott, R. and Lee, S. K. and ten Haken, B. and Trabesinger, A. H. and Pines, A. and Clarke, J.} }