SQUID-Based Microtesla MRI for In Vivo Relaxometry of the Human Brain

SQUID-based MRI (magnetic resonance imaging) at microtesla fields has developed significantly over the past few years. Here we describe application of this method for magnetic relaxation measurements in the living human brain. We report values of the longitudinal relaxation time T1 for brain tissues, measured in vivo for the first time at microtesla fields. The experiments were performed at 46 muT field using a seven-channel SQUID system designed for microtesla MRI and MEG. Values of T1, measured for different tissues at this field, are found to be close (within 5%) to the corresponding values of the transverse relaxation time T2 at the same field. Implications of this result for imaging contrast in microtesla MRI are discussed.

[1]  Robert H Kraus,et al.  Parallel MRI at microtesla fields. , 2008, Journal of magnetic resonance.

[2]  I. Solomon.  Relaxation Processes in a System of Two Spins , 1955 .

[3]  Seymour H. Koenig,et al.  Field-cycling relaxometry of protein solutions and tissue: Implications for MRI , 1990 .

[4]  A. N. Matlashov,et al.  SQUID-based instrumentation for ultralow-field MRI , 2007 .

[5]  John S George,et al.  SQUID detected NMR in microtesla magnetic fields. , 2004, Journal of magnetic resonance (San Diego, Calif. 1997 : Print).

[6]  John S George,et al.  Simultaneous magnetoencephalography and SQUID detected nuclear MR in microtesla magnetic fields , 2004, Magnetic resonance in medicine.

[7]  J. Mosher,et al.  Multi-Channel SQUID System for MEG and Ultra-Low-Field MRI , 2006, IEEE transactions on applied superconductivity.

[8]  J. Mosher,et al.  SQUID-based simultaneous detection of NMR and biomagnetic signals at ultra-low magnetic fields , 2005, IEEE Transactions on Applied Superconductivity.

[9]  S. H. Koenig,et al.  Determinants of Proton Relaxation Rates in Tissue , 1984, Magnetic resonance in medicine.

[10]  Robert McDermott,et al.  Microtesla MRI with a superconducting quantum interference device. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[11]  Robert H Kraus,et al.  Microtesla MRI of the human brain combined with MEG. , 2008, Journal of magnetic resonance.

[12]  John Clarke,et al.  SQUID‐detected MRI at 132 μT with T1‐weighted contrast established at 10 μT–300 mT , 2005 .

[13]  S. Holland,et al.  NMR relaxation times in the human brain at 3.0 tesla , 1999, Journal of magnetic resonance imaging : JMRI.

[14]  P A Rinck,et al.  Nuclear relaxation of human brain gray and white matter: Analysis of field dependence and implications for MRI , 1990, Magnetic resonance in medicine.