New magnet designs for MR

Hawksworth, D.

doi:10.1002/mrm.1910170107

Cited by 7 publications

(1 citation statement)

References 4 publications

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“…A particular advantage is the ªopennessº of non-cylindrical designs. The design of friendlier, less claustrophobic superconducting magnets remains a challenge for magnet designers [3].…”

Section: Magnet Systemmentioning

confidence: 99%

MRI - From basic knowledge to advanced strategies: Hardware

Carpenter

Williams

1999

European Radiology

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There have been remarkable advances in the hardware used for nuclear magnetic resonance imaging scanners. These advances have enabled an extraordinary range of sophisticated magnetic resonance MR sequences to be performed routinely. This paper focuses on the following particular aspects: (a) Magnet system. Advances in magnet technology have allowed superconducting magnets which are low maintenance and have excellent homogeneity and very small stray field footprints. (b) Gradient system. Optimisation of gradient design has allowed gradient coils which provide excellent field for spatial encoding, have reduced diameter and have technology to minimise the effects of eddy currents. These coils can now routinely provide the strength and switching rate required by modern imaging methods. (c) Radio-frequency (RF) system. The advances in digital electronics can now provide RF electronics which have low noise characteristics, high accuracy and improved stability, which are all essential to the formation of excellent images. The use of surface coils has increased with the availability of phased-array systems, which are ideal for spinal work. (d) Computer system. The largest advance in technology has been in the supporting computer hardware which is now affordable, reliable and with performance to match the processing requirements demanded by present imaging sequences.

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“…A particular advantage is the ªopennessº of non-cylindrical designs. The design of friendlier, less claustrophobic superconducting magnets remains a challenge for magnet designers [3].…”

Section: Magnet Systemmentioning

confidence: 99%

MRI - From basic knowledge to advanced strategies: Hardware

Carpenter

Williams

1999

European Radiology

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Magnetic Resonance Imaging

Prost¹

2002

Encyclopedia of Imaging Science and Technology

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Imaging of materials that contain nuclei of nonzero spin values has become a valuable tool in science, medicine, and industry. The principal use of MRI is to create an image of the distribution of certain physical properties of a substance, whether in the fluid‐filled rock surrounding an oil well, soil, food‐processing, industrial process control or a human subject. These physical properties imaged include the chemistry of the material, its fluidity, its interactions with other materials in the molecular‐level neighborhood, and even the flow of liquids within the object. Magnetic resonance phenomena occur on a timescale that is short relative to many chemical reactions and can often be used to investigate the kinetics of chemical reactions. Many different elements are amenable to investigation by magnetic resonance, but the sensitivity of MR is poor. As a result of this insensitivity, magnetic resonance is not suited to detecting of chemical moities of less than millimolar quantities. For the same reason, gases are largely unsuitable to investigation by magnetic resonance, except for hyperpolarized gases 3 He and 129 Xe. All solid or liquid objects, that bear suitable nuclei can be imaged. However, spins within solid materials lose their signal on a very short timescale. This brevity of signal lifetime makes imaging quite difficult, yet not impossible. Examples of nuclei that bear a magnetic moment, or nonzero spin include hydrogen, helium‐3, xenon‐129, phosphorus, lithium, fluorine, carbon‐13 and sodium‐23. An important and recent use of the MR phenomenon is in medical imaging. The reason for the success of MRI in medical imaging is fourfold. The first is the abundance of hydrogen in the human body. Hydrogen nuclei in the brain are about 70 Molar in concentration which is much higher than any other material that can be detected by NMR. The second is that the hydrogen is distributed in the organs in a way which allows using the MR signal to create images. The third is that imaging of hydrogen produces exquisitely detailed images of internal organ structure. The fourth is the functional data that can be extracted. These data include molecular diffusion, distribution of chemical moieties, flow, flow in the capillary bed, oxygen utilization, magnetization transfer rates, and disruption of the blood–brain barrier. Basic MRI physics, imaging processing and k‐space, endogenous image contract and other mechanisms are discussed.

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Invited. MR systems for image‐guided therapy

Hinks

Bronskill

Kucharczyk

et al. 1998

Magnetic Resonance Imaging

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The use of MRI to guide and monitor interventional procedures requires the merging of surgical and MRI environments. The ideal magnet shape for homogeneity and efficiency is spherical, but this design provides no access. Opening the sphere to provide both patient and surgeon access suggests cylindrical or biplanar magnets. Cylindrical magnets have poor surgical access but provide good imaging capabilities, which can be used in conjunction with a neighboring but distinct surgical environment. Biplanar magnets provide more and better approaches to the patient, but generally with lower field strength. Vertical biplanar systems allows surgical approaches from above but reduce the access of support staff to the patient. A hybrid magnet design, which combines the benefits of both cylindrical and biplanar magnets, can provide increased access with simultaneous approach from two sides of the patient. Application-specific magnets can target a smaller region, leading to compact magnet designs that greatly expand access for both surgical intervention as well as patient support. As the field of interventional MRI matures, the suitability of each design to specific applications will be better understood, leading to more integrated system designs tailored to the needs of image-guided therapy.

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New magnet designs for MR

Abstract: The evolution of MRI magnets is reviewed. New magnet developments are discussed with reference to improved performance, novel system features, and lower cost.

Cited by 7 publications

References 4 publications

MRI - From basic knowledge to advanced strategies: Hardware

MRI - From basic knowledge to advanced strategies: Hardware

Magnetic Resonance Imaging

Invited. MR systems for image‐guided therapy

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