Design and Development of a Helmholtz Pair System for Production of a Low-Magnetic Field of up to 7.5 mT

In this study, the design, numerical modelling, and construction of various Helmholtz pair coil systems were investigated to produce a homogeneous magnetic field. The magnetic field was simulated using three different Helmholtz coil systems including 2-coil, 3-coil, and 4-coil combinations in order to optimize the field homogeneity and strength over a region of interest that consists of a cylindrical geometry with a height of 700 mm and a diameter of 90 mm. The simulated magnetic field created by the 4-coil system was found to be more homogenous than 3-coil and 2-coil systems over the region of interest. The 4-coil system was constructed and tested by using two commercially available low-power (P=600 W) DC power supplies. For further optimization, the number of turns and diameter of coil elements were simulated. The optimum number of turns and elements were determined to be 140 and 80 turns for the outer pair and inner pair of the 4-coil system, respectively. Finally, the produced magnetic field strength was measured using a hand-held gaussmeter and compared to the simulated magnetic field. We found that the system can produce a magnetic field of B=7.5047 ± 0.0562 mT, and the correlation between simulated and measured magnetic fields were calculated to be R=0.9824 with (p<0.001) suggesting a statistically significant agreement.

Keywords:

Helmholtz Coil, Magnetic Field, Spin Exchange Optical Pumping,

PDF

___

Hatta, J., et al., "SQUID-Based Low Field MRI System for Small Animals". Ieee Transactions on Applied Superconductivity. 21(3): p. 526-529. 2011.
Campbell-Washburn, A.E., et al., "Opportunities in Interventional and Diagnostic Imaging by Using High-Performance Low-Field-Strength MRI". Radiology. 293(2): p. 384-393. 2019.
Tavernier, T. and A. Cotten, "High- versus low-field MR imaging". Radiol Clin North Am. 43(4): p. 673-81, viii. 2005.
Dominguez-Viqueira, W., et al., "A variable field strength system for hyperpolarized noble gas MR imaging of rodent lungs". Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering. 33b(2): p. 124-137. 2008.
Wong, G.P., et al., "A system for low field imaging of laser-polarized noble gas". Journal of Magnetic Resonance. 141(2): p. 217-227. 1999.
Tseng, C.H., et al., "Low-field MRI of laser polarized noble gas". Physical Review Letters. 81(17): p. 3785-3788. 1998.
Mair, R.W., et al., "He-3 lung imaging in an open access, very-low-field human magnetic resonance imaging system". Magnetic Resonance in Medicine. 53(4): p. 745-749. 2005.
Coffey, A.M., et al., "High-Resolution Low-Field Molecular Magnetic Resonance Imaging of Hyperpolarized Liquids". Analytical Chemistry. 86(18): p. 9042-9049. 2014.
Doganay, O., et al., "Fast dynamic ventilation MRI of hyperpolarized Xe-129 using spiral imaging". Magnetic Resonance in Medicine. 79(5): p. 2597-2606. 2018.
Doganay, O., et al., "Time-series hyperpolarized xenon-129 MRI of lobar lung ventilation of COPD in comparison to V/Q-SPECT/CT and CT". European Radiology. 29(8): p. 4058-4067. 2019.
Zheng, Y., et al., "Very-low-field MRI of laser polarized xenon-129". Journal of Magnetic Resonance. 249: p. 108-117. 2014.
Patz, S., et al., "Human pulmonary imaging and spectroscopy with hyperpolarized Xe-129 at 0.2T". Academic Radiology. 15(6): p. 713-727. 2008.
Ruset, I.C., et al., "A system for open-access He-3 human lung imaging at very low field". Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering. 29b(4): p. 210-221. 2006.
Coffey, A.M., et al., "High-resolution hyperpolarized in vivo metabolic C-13 spectroscopy at low magnetic field (48.7 mT) following murine tail-vein injection". Journal of Magnetic Resonance. 281: p. 246-252. 2017.
Norquay, G., et al., "Xe-129-Rb Spin-Exchange Optical Pumping with High Photon Efficiency". Physical Review Letters. 121(15). 2018.
Driehuys, B., J. Pollaro, and G.P. Cofer, "In vivo MRI using real-time production of hyperpolarized Xe-129". Magnetic Resonance in Medicine. 60(1): p. 14-20. 2008.
Nikolaou, P., et al., "A 3D-Printed High Power Nuclear Spin Polarizer". Journal of the American Chemical Society. 136(4): p. 1636-1642. 2014.
Hersman, F.W., et al., "Large production system for hyperpolarized Xe-129 for human lung imaging studies". Academic Radiology. 15(6): p. 683-692. 2008.
Cooley, C.Z., et al., "Two-Dimensional Imaging in a Lightweight Portable MRI Scanner without Gradient Coils". Magnetic Resonance in Medicine. 73(2): p. 872-883. 2015.
McDaniel, P.C., et al., "The MR Cap: A single-sided MRI system designed for potential point-of-care limited field-of-view brain imaging". Magn Reson Med. 82(5): p. 1946-1960. 2019.
O'Reilly, T., et al., "In vivo 3D brain and extremity MRI at 50 mT using a permanent magnet Halbach array". Magn Reson Med. 85(1): p. 495-505. 2021.
Doganay, O., et al., "Magnetic resonance imaging of the time course of hyperpolarized Xe-129 gas exchange in the human lungs and heart". European Radiology. 29(5): p. 2283-2292. 2019.
Judeinstein, P., et al., "Low-field single-sided NMR for one-shot 1D-mapping: Application to membranes". J Magn Reson. 277: p. 25-29. 2017.
Tourell, M.C., et al., "T(1) -based sensing of mammographic density using single-sided portable NMR". Magn Reson Med. 80(3): p. 1243-1251. 2018.
Schill, R.A., "General relation for the vector magnetic field of a circular current loop: A closer look". Ieee Transactions on Magnetics. 39(2): p. 961-967. 2003.
García-Farieta, J.E. and A.H. Márquez, "Exploring the magnetic field of Helmholtz and Maxwell coils: a computer-based approach exploiting the superposition principle". Revista Brasileira de Ensino de Física. 42. 2020.
Restrepo, A.F., et al., "A comparative study of the magnetic field homogeneity for circular, square and equilateral triangular Helmholtz coils". 2017 International Conference on Electrical, Electronics, Communication, Computer, and Optimization Techniques (Iceeccot): p. 13-20. 2017.
Gyawali, S.R. and N.E. Islam, Design and construction of helmholtz coil for biomagnetic studies on soybean. 2008, University of Missouri-Columbia,: Columbia, Mo.
Mullen, M. and M. Garwood, "Contemporary approaches to high-field magnetic resonance imaging with large field inhomogeneity". Prog Nucl Magn Reson Spectrosc. 120-121: p. 95-108. 2020.