Safety and Sensory Aspects of Main and Gradient Fields in MRI

Schenck, John F.

doi:10.1002/9780470034590.emrstm1324

Cited by 3 publications

(1 citation statement)

References 87 publications

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“…For thermal treatment monitoring, MRI currently offers many of the most practical and widely available methods to accurately and non-invasively measure temperature inside the human body. Using MRI does require that the therapy equipment should not interact with the radio frequency (RF), gradient, and main magnetic fields of the MRI scanner, and that any magnetic or inducible parts be far from the MRI scanner [2][3][4][5][6][7]. Further, the presence of various biomedical implants and devices in the body may pose hazards for patients undergoing MR procedures, and thorough screening before any scan is important [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Magnetic resonance thermometry and its biological applications – Physical principles and practical considerations

Odéen

Parker

2019

Progress in Nuclear Magnetic Resonance Spectroscopy

116

112

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Most parameters that influence the magnetic resonance imaging (MRI) signal experience a temperature dependence. The fact that MRI can be used for non-invasive measurements of temperature and temperature change deep inside the human body has been known for over 30 years. Today, MR temperature imaging is widely used to monitor and evaluate thermal therapies such as radio frequency, microwave, laser, and focused ultrasound therapy. In this paper we cover the physical principles underlying the biological applications of MR temperature imaging and discuss practical considerations and remaining challenges. For biological tissue, the MR signal of interest comes mostly from hydrogen protons of water molecules but also from protons in, e.g., adipose tissue and various metabolites. Most of the discussed methods, such as those using the proton resonance frequency (PRF) shift, T 1 , T 2 , and diffusion only measure temperature change, but measurements of absolute temperatures are also possible using spectroscopic imaging methods (taking advantage of various metabolite signals as internal references) or various types of contrast agents. Currently, the PRF method is the most used clinically due to good sensitivity, excellent linearity with temperature, and because it is largely independent of tissue type. Because the PRF method does not work in adipose tissues, T 1 -and T 2 -based methods have recently gained interest for monitoring temperature change in areas with high fat content such as the breast and abdomen. Absolute temperature measurement methods using spectroscopic imaging and contrast agents often offer too low spatial and temporal resolution for accurate monitoring of ablative thermal procedures, but have shown great promise in monitoring the slower and usually less spatially localized temperature change observed during hyperthermia procedures. Much of the current research effort for ablative procedures is aimed at providing faster measurements, larger field-ofview coverage, simultaneous monitoring in aqueous and adipose tissues, and more motioninsensitive acquisitions for better precision measurements in organs such as the heart, liver, and kidneys. For hyperthermia applications, larger coverage, motion insensitivity, and simultaneous aqueous and adipose monitoring are also important, but great effort is also aimed at solving the problem of long-term field drift which gets interpreted as temperature change when using the PRF method.

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Section: Introductionmentioning

confidence: 99%

Magnetic resonance thermometry and its biological applications – Physical principles and practical considerations

Odéen

Parker

2019

Progress in Nuclear Magnetic Resonance Spectroscopy

116

112

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MRI Safety

Brau¹,

Hardy²,

Schenck³

2015

Basic Principles of Cardiovascular MRI

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Design requirements for human UHF magnets from the perspective of MRI scientists

Ladd,

Quick,

Scheffler

et al. 2024

Supercond. Sci. Technol.

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The highest magnetic field strength for human-sized magnetic resonance imaging (MRI) currently lies at 11.7 tesla. Given the opportunities for enhanced sensitivity and improved data quality at higher static magnetic fields, several initiatives around the world are pursuing the implementation of further human MRI systems at or above 11.7 tesla. In general, members of the MR research community are not experts on magnet technology. However, the magnet is the technological heart of any MR system, and the MRI community is challenging the magnet research and design community to fulfill the current engineering gap in implementing large-bore, highly homogeneous and stabile magnets at field strengths that go beyond the performance capability of niobium-titanium. In this article, we present an overview of magnet design for such systems from the perspective of MR scientists. The underlying motivation and need for higher magnetic fields are briefly introduced, and system design considerations for the magnet as well as for the MRI subsystems such as the gradients, the shimming arrangement, and the radiofrequency hardware are presented. Finally, important limitations to higher magnetic fields from physiological considerations are described, operating under the assumption that any engineering or economic barriers to realizing such systems will be overcome.

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Safety and Sensory Aspects of Main and Gradient Fields in MRI

Cited by 3 publications

References 87 publications

Magnetic resonance thermometry and its biological applications – Physical principles and practical considerations

Magnetic resonance thermometry and its biological applications – Physical principles and practical considerations

MRI Safety

Design requirements for human UHF magnets from the perspective of MRI scientists

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