Low-field magnetic resonance

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The low field nuclear magnetic resonance refers to the generation of nuclear spin resonance means of weak magnetic fields in milli Tesla range. The principle is used in special forms of imaging diagnostics ( magnetic resonance tomography , MRT), in analytics ( magnetic resonance spectroscopy , MRS) and in therapeutic nuclear magnetic resonance. Studies show diagnostic accuracy and high sensitivity in musculoskeletal imaging .

properties

To generate nuclear magnetic resonance, a homogeneous magnetic field and a high-frequency alternating field in the high-frequency range are required . If the field strength of the homogeneous magnetic field is less than in the order of magnitude of 0.5 Tesla, the resulting magnetic resonance is referred to as low-field magnetic resonance.

Nuclear magnetic resonance, which is generated by magnetic fields in the range 0.001 T to 0.1 T, is often called ultra-low-field magnetic resonance. Studies have shown that nuclear magnetic resonance can in principle be generated at field strengths down to the nanotesla range. For comparison: The geomagnetic field in Europe has an amount of about 0.05 mT = 50,000 nT.

application areas

Low-field magnetic resonance imaging

Low-field magnetic resonance imaging is used in clinical imaging . The field strengths used for this application are predominantly between 0.2 and 0.5 T. Compared to high-field magnetic resonance tomography, low-field magnetic resonance tomography has a lower signal-to-noise ratio , which results in less good resolution and therefore higher scanning times are required .

The advantages of this technology lie in the contrast differences, which are better for different tissue types with smaller field strengths than with larger field strengths. Smaller magnetic field strengths also enable a smaller design. This makes the use of the MRT much more comfortable for patients with claustrophobic preload, because the central opening of the MRT can be selected to be larger.

Low-field magnetic resonance tomography is a suitable instrument for assessing the course of diseases and is mostly used to examine specific body parts (e.g. wrists) due to the high contrast differences.

In principle, an image construction is still possible with magnetic field strengths in the millite-size range.

Low field NMR spectroscopy

Low-field NMR spectroscopy is used in analytical chemistry. This makes it possible to consider other relaxation processes than with conventional NMR. The line width of an NMR signal scales with the measured magnetic field. This leads to narrow line widths in small fields. SQUIDs (superconducting quantum interference units) are used to detect the signal .

Therapeutic nuclear magnetic resonance

Another area of ​​application of low-field magnetic resonance is therapeutic nuclear magnetic resonance, which is used to treat painful changes in the musculoskeletal system.

Individual evidence

  1. ↑ MA Carsten, JI Kaplan: Low-Field Magnetic Resonance . In: Physical Review . tape 99 , no. 2 , July 15, 1955, p. 459-463 , doi : 10.1103 / PhysRev.99.459 .
  2. ↑ Jamshid Tehranzadeh, Oganes Ashikyan, Jane Dascalos: Advanced imaging of early rheumatoid arthritis . In: Radiologic Clinics of North America . tape 42 , no. 1 , January 2004, p. 89-107 , doi : 10.1016 / S0033-8389 (03) 00167-2 , PMID 15049525 .
  3. ↑ Robert Pedowitz, Christine B. Chung, Donald Resnick: Magnetic Resonance Imaging in Orthopedic Sports Medicine . Springer, 2008, ISBN 978-0-387-48897-4 .
  4. ^ Martin Burghoff, Stefan Hartwig, Lutz Trahms, Johannes Bernarding: Nuclear magnetic resonance in the nanoTesla range . In: Applied Physics Letters . tape 87 , no. 5 , July 27, 2005, p. 054103 , doi : 10.1063 / 1.2006981 .
  5. ^ National Geophysical Data Center
  6. ^ Brian K. Rutt, Donald H. Lee: The impact of field strength on image quality in MRI . In: Journal of Magnetic Resonance Imaging . tape 6 , no. 1 , 1996, p. 57-62 , doi : 10.1002 / jmri.1880060111 .
  7. ↑ BJ Ejbjerg, E. Narvestad, S. Jacobsen, HS Thomsen, M. Østergaard: Optimized, Low Cost, Low Field Dedicated Extremity MRI Is Highly Specific and Sensitive for Synovitis and Bone Erosion in Rheumatoid Arthritis Wrist and Finger Joints: Comparison with Conventional High Field MRI and Radiography . In: Annals of the Rheumatic Diseases . tape 64 , no. 9 , January 9, 2005, p. 1280-1287 , doi : 10.1136 / ard.2004.029850 .
  8. ↑ K. Schlenga, R. McDermott, John Clarke, RE de Souza, A. Wong-Foy, A. Pines: Low-field magnetic resonance imaging with a high-T c dc superconducting quantum interference device . In: Applied Physics Letters . tape 75 , no. 23 , December 6, 1999, pp. 3695-3697 , doi : 10.1063 / 1.125432 .
  9. ↑ Longqing Qiu, Yi Zhang, Hans-Joachim Krause, Alex I. Braginski, Andreas Offenhäusser: Low-field NMR measurement procedure when SQUID detection is used . In: Journal of Magnetic Resonance . tape 196 , no. 2 , February 2009, p. 101-104 , doi : 10.1016 / y.jmr.2008.09.009 .
  10. ↑ G. Salomonowitz, H. Salfinger, J. Hahne, M. Friedrich: Effects of magnetic resonance therapy on sick leave in patients with nerve root irritation as a result of a lumbar disc herniation . In: Journal of Orthopedics and Trauma Surgery . tape 149 , no. 05 , October 7, 2011, p. 575-581 , doi : 10.1055 / s-0031-1280121 .
  11. ↑ Thomas Brockamp: Does nuclear magnetic resonance therapy have an influence on post-traumatic osteoarthritis of the knee in the rabbit model? 2009, urn : nbn: de: hbz: 6-01599389512 (dissertation, University of Münster, 2009).