Abstract
Background For more than two decades, the focus of technological progress in MRI was restricted
to systems with a field strength of 1.5 T and higher. Low- and mid-field MRI systems,
which offer some specific advantages, are vanishing from the market. This article
is intended to initiate a re-evaluation of the factor ‘field strength’ in MR imaging.
Method Literature review was carried out using MEDLINE database (via Pubmed) over a time
span from 1980 to 2019 using free-text and Medical Subject headings (MeSH). Article
selection was based on relevance and evidence.
Results and Conclusion Low-field MR systems are meanwhile rare in clinical imaging. MRI systems with a lower
field strength provide a reduced signal-noise ratio (SNR) and spectral differentiation.
However, these systems offer a variety of advantages: Shorter T1 relaxation, better
T1 contrast, fewer metal artifacts, reduced susceptibility and chemical shift artifacts,
fewer dielectric effects, better tissue penetration, less RF-power deposition, fewer
‘missile effects’, reduced effect on biomedical implants such as shunt valves, less
energy and helium consumption. If we free ourselves from the constraints of high-field
strength, we are able to offer multiple medical, economic and ecologic advantages
to our patients. The development of high-quality low-field MRI is possible and necessary.
Key Points:
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Static magnetic field strength is only one of many parameters influencing image quality
in MR imaging.
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Lower field strength results in a lower signal-to-noise ratio (SNR).
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Modern MR systems offer technical tools to improve signal strength and reduce noise.
This makes it possible to provide a diagnostic SNR at a lower field strength.
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Low-field MR systems offer important advantages which have to be made available to
our patients.
Citation Format
Key words
safety - technical aspects - physics - MR imaging
