MRI Gradient Coils with Improved Stimulation Threshold

Summary

Principal Investigator: Christopher Collins
Abstract: With currently available high-power gradient amplifiers, magnetic resonance imaging (MRI) studies requiring strong, rapidly switched gradient fields are limited in speed, resolution, or accuracy due to the induction of PNS. They propose to develop, apply, and verify an accurate and efficient method for gradient coil design with consideration of peripheral nerve stimulation (PNS): SPECIFIC AIM 1: Develop fast and accurate 3 dimensional (3D) numerical method to calculate the electric fields induced in weakly conductive dielectric samples during the operation of pulsed magnetic coils. This will be accomplished by: 1. measurement of the electrical fields induced in simple liquid phantoms by magnetic coils to serve as a gold standard, 2. evaluation of existing and proposed numerical methods by comparison to gold standard experimental measurements. SPECIFIC AIM 2: Establish a calibration of calculated fields to PNS thresholds. This will be accomplished by: 1. measurement of stimulation thresholds and locations in human subjects exposed to existing high strength head gradient coils and, 2. calculation of electrical fields in a realistic multi-tissue human model in the head gradient coil and identification of electrical field values in locations of stimulation corresponding to the measured PNS thresholds. SPECIFIC AIM 3: Use calibrated numerical calculations to design a prototype head gradient coil with improved PNS threshold and verify performance in human subjects. This will be accomplished by: 1. calculation of PNS thresholds for variations of several candidate gradient coil designs and using optimization routine to identify optimal design, 2. construction of a prototype of the optimal coil, 3. verification of improved PNS thresholds of human volunteers in the prototype coil. Accomplishment of these aims will require significant engineering of the interaction between magnetic fields and the human body. In line with the program announcement, this proposal will produce instruments (gradient coils), techniques (coil design methods), and software (field calculation and coil design algorithms) toward more powerful and more precise technology for biomedical research. This work will lay the foundation for development of clinically useful head and body gradient coils that can outperform existing coils before inducing PNS.
Funding Period: 2003-04-01 - 2006-03-31
more information: NIH RePORT

Top Publications

  1. ncbi Sensory and motor stimulation thresholds of the ulnar nerve from electric and magnetic field stimuli: implications to gradient coil operation
    Bryan J Recoskie
    Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
    Magn Reson Med 64:1567-79. 2010
  2. ncbi Consideration of magnetically-induced and conservative electric fields within a loaded gradient coil
    Weihua Mao
    Department of Radiology, Pennsylvania State University College of Medicine, Hershey, 17033, USA
    Magn Reson Med 55:1424-32. 2006
  3. pmc Numerical field calculations considering the human subject for engineering and safety assurance in MRI
    Christopher M Collins
    Department of Radiology, The Pennsylvania State University, Hershey, PA 17033 0850, USA
    NMR Biomed 22:919-26. 2009
  4. ncbi The discrepancy between human peripheral nerve chronaxie times as measured using magnetic and electric field stimuli: the relevance to MRI gradient coil safety
    Bryan J Recoskie
    Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
    Phys Med Biol 54:5965-79. 2009

Scientific Experts

  • Christopher Collins
  • Bryan J Recoskie
  • Blaine A Chronik
  • Timothy J Scholl
  • Weihua Mao
  • Martin Zinke-Allmang
  • Michael B Smith
  • Rebecca E Feldman

Detail Information

Publications4

  1. ncbi Sensory and motor stimulation thresholds of the ulnar nerve from electric and magnetic field stimuli: implications to gradient coil operation
    Bryan J Recoskie
    Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
    Magn Reson Med 64:1567-79. 2010
    ..Based on these observations, significant adjustments may need to be made to nerve parameters taken from the electric field stimulation literature prior to applying them directly to gradient induced stimulation in MRI...
  2. ncbi Consideration of magnetically-induced and conservative electric fields within a loaded gradient coil
    Weihua Mao
    Department of Radiology, Pennsylvania State University College of Medicine, Hershey, 17033, USA
    Magn Reson Med 55:1424-32. 2006
    ....
  3. pmc Numerical field calculations considering the human subject for engineering and safety assurance in MRI
    Christopher M Collins
    Department of Radiology, The Pennsylvania State University, Hershey, PA 17033 0850, USA
    NMR Biomed 22:919-26. 2009
    ....
  4. ncbi The discrepancy between human peripheral nerve chronaxie times as measured using magnetic and electric field stimuli: the relevance to MRI gradient coil safety
    Bryan J Recoskie
    Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
    Phys Med Biol 54:5965-79. 2009
    ..However, this result does motivate us to suggest that special care must be taken when using electric field exposure data from the literature to set gradient coil PNS safety standards in MRI...