Magnetic Resonance - Technology Information Portal Welcome to MRI Technology••


Acoustic Noise Reduction (Silent, Quiet, etc.) :
cannot get better 
is in its first steps 
is done by earplugs, headphones 
must get better 
is bad, I miss something 
is unnecessary 

MRI Devices, Systems
  • Types of Magnets
Ultrasound Imaging Systems Open this link in a new window
A type of magnet that utilizes coils of wire, typically wound on an iron core, so that as current flows through the coil it becomes magnetized. The direction of the magnetic field is parallel to the long axis of the coil. Whole body electromagnets, used in medical imaging (also called resistive) are limited to their field strength, because the weight becomes prohibitively large at high field MRI. The magnetic field shuts down, if the current is switched of. Because this type of magnet generates heat, a good cooling system is essential.
For a stronger magnetic field, the wires must be manufactured of superconducting materials to reduce the power needed to produce the field.
See also Resistive Magnet, Superconducting Magnet and Upright™ MRI

• View the NEWS results for 'Electromagnet' (8).Open this link in a new window.

• View the DATABASE results for 'Electromagnet' (24).Open this link in a new window

Further Reading:
What types of magnets are there?
  News & More:
Continued access to MRI for patients in Europe
Wednesday, 12 June 2013   by    
Concentration And Visuospatial Awareness Affected By MRI Scanners
Thursday, 30 August 2012   by    
'Electromagnetic Wormhole' Possible with Invisibility Technology
Monday, 15 October 2007   by    
Superconductors Face the Future
Wednesday, 15 September 2010   by    
Permanent Magnet 
A magnet whose magnetic field originates from permanently ferromagnetic materials (permanent magnets) to generate a magnetic field between the two poles of the magnet. There is no requirement for additional electrical power or cooling, and the iron-core structure of the magnet leads to a limited fringe field and no missile effect. Due to weight considerations, permanent magnets are usually limited to maximum field strengths of 0.4 T. The main disadvantages of a permanent magnet are the cost of the magnet itself and supporting structures and the varying changes in the magnetic field. Field homogeneity can be an on-going problem in permanent magnets.

• View the NEWS results for 'Permanent Magnet' (2).Open this link in a new window.

• View the DATABASE results for 'Permanent Magnet' (15).Open this link in a new window

Further Reading:
What types of magnets are there?
  News & More:
Magnetic Field
Resistive Magnet 
A type of magnet that utilizes the principles of electromagnetism to generate the magnetic field. Typically large current values and significant cooling of the magnet coils is required. The resistive magnet does not require cryogens, but needs a constant power supply to maintain a homogenous magnetic field, and can be quite expensive to maintain.
Resistive magnets fall into two general categories - iron-core and air-core.
Iron-core electromagnets provide the advantages of a vertically oriented magnetic field, and a limited fringe field with little, if any, missile effects due to the closed iron-flux return path.
Air-core electromagnets exhibit horizontally oriented fields, which have large fringe fields (unless magnetically shielded) and are prone to missile effects. Resistive magnets are typically limited to maximum field strengths of approximately 0.6T.

• View the DATABASE results for 'Resistive Magnet' (3).Open this link in a new window

Superconducting Magnet 
Superconducting magnets are electromagnets that are partially built from superconducting materials and therefore reach much higher magnetic field intensity.
The coil windings of superconducting magnets are made of wires of a type 2 superconductor (mostly used is niobium-titanium - up to 15 Tesla the critical temperature is less then 10 Kelvin). These coils have no resistance when operated at temperatures near absolute zero (-273.15°C, -459°F, 0 K).
Liquid helium (4.2 K) is commonly used as a coolant (sometimes in addition with a second cryogen liquid nitrogen as an intermediate thermal shield to reduce the boil-off rate of liquid helium), which consequently conclude refilling (intervals: liquid helium ~ 3 month, liquid nitrogen ~ 2 weeks). There are cryogen-free superconducting magnets with a closed-cycle refrigerating system at the horizon. Superconducting magnets typically exhibit field strengths of greater than 0.5 T, operate clinically up to 3 T, and have a horizontal field orientation, which makes them prone to missile effects without significant magnetic shielding.
See also Quenching.
See also the related poll result: 'In 2010 your scanner will probably work with a field strength of'

• View the NEWS results for 'Superconducting Magnet' (3).Open this link in a new window.

• View the DATABASE results for 'Superconducting Magnet' (15).Open this link in a new window

Further Reading:
Superconducting Magnets
Magnetic Field of the Strongest Magnet
2003   by    
  News & More:
Age of Super Conductors has began
Monday, 1 February 2016   by    
A hot time for cold superconductors
Tuesday, 9 December 2003   by    
Hybrid Magnet 
Magnet system employing both current-carrying coils and permanently magnetized material to generate the magnetic field.
Further Reading:
High-field and Hybrid
Thursday, 6 March 2014   by    
  News & More:
Molecular imaging and radiochemistry: the importance of instrumentation. An interview with Professor Bjorn Wangler
Thursday, 4 February 2016   by    
Researchers to develop new hybrid PET/MRI system for improved breast cancer diagnosis
Wednesday, 27 January 2016   by    
  Devices - Overview top
Ultrasound Imaging Systems Open this link in a new window
If A is success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut.
- Albert Einstein
Share This Page

Forgot your UserID/Password ?  

      Ups uses cookies! By browsing, you agree to our use of cookies.

Magnetic Resonance - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • US-TIP • 
Copyright © 2003 - 2018 SoftWays. All rights reserved. [ 12 December 2018]
Terms of Use | Privacy Policy | Advertising
 [last update: 2018-03-08 05:11:00]