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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'
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• Related Searches:
    • Magnet
    • Device
    • Superconductive
    • Helium
    • Boil off Rate
 
Further Reading:
  Basics:
Superconducting Magnets
   by hyperphysics.phy-astr.gsu.edu    
Magnetic Field of the Strongest Magnet
2003   by hypertextbook.com    
  News & More:
Age of Super Conductors has began
Monday, 1 February 2016   by www.albanydailystar.com    
A hot time for cold superconductors
Tuesday, 9 December 2003   by www.brightsurf.com    
MRI Resources 
Shielding - MRA - MRI Technician and Technologist Schools - Societies - Stent - Nerve Stimulator
 
DeviceForum -
related threadsInfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.
 
Magnetic resonance imaging (MRI) is based on the magnetic resonance phenomenon, and is used for medical diagnostic imaging since ca. 1977 (see also MRI History).
The first developed MRI devices were constructed as long narrow tunnels. In the meantime the magnets became shorter and wider. In addition to this short bore magnet design, open MRI machines were created. MRI machines with open design have commonly either horizontal or vertical opposite installed magnets and obtain more space and air around the patient during the MRI test.
The basic hardware components of all MRI systems are the magnet, producing a stable and very intense magnetic field, the gradient coils, creating a variable field and radio frequency (RF) coils which are used to transmit energy and to encode spatial positioning. A computer controls the MRI scanning operation and processes the information.
The range of used field strengths for medical imaging is from 0.15 to 3 T. The open MRI magnets have usually field strength in the range 0.2 Tesla to 0.35 Tesla. The higher field MRI devices are commonly solenoid with short bore superconducting magnets, which provide homogeneous fields of high stability.
There are this different types of magnets:
Resistive Magnet
Permanent Magnet
Superconducting Magnet
The majority of superconductive magnets are based on niobium-titanium (NbTi) alloys, which are very reliable and require extremely uniform fields and extreme stability over time, but require a liquid helium cryogenic system to keep the conductors at approximately 4.2 Kelvin (-268.8 Celsius). To maintain this temperature the magnet is enclosed and cooled by a cryogen containing liquid helium (sometimes also nitrogen).
The gradient coils are required to produce a linear variation in field along one direction, and to have high efficiency, low inductance and low resistance, in order to minimize the current requirements and heat deposition. A Maxwell coil usually produces linear variation in field along the z-axis; in the other two axes it is best done using a saddle coil, such as the Golay coil.
The radio frequency coils used to excite the nuclei fall into two main categories; surface coils and volume coils. The essential element for spatial encoding, the gradient coil sub-system of the MRI scanner is responsible for the encoding of specialized contrast such as flow information, diffusion information, and modulation of magnetization for spatial tagging.
An analog to digital converter turns the nuclear magnetic resonance signal to a digital signal. The digital signal is then sent to an image processor for Fourier transformation and the image of the MRI scan is displayed on a monitor.

For Ultrasound Imaging (USI) see Ultrasound Machine at US-TIP.com.

See also the related poll results: 'In 2010 your scanner will probably work with a field strength of' and 'Most outages of your scanning system are caused by failure of'
Radiology-tip.comGamma Camera,  Linear Accelerator
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Radiology-tip.comUltrasound Machine,  Real-Time Scanner
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• View the DATABASE results for 'Device' (141).Open this link in a new window


• View the NEWS results for 'Device' (29).Open this link in a new window.
 
Further Reading:
  News & More:
Kyoto University and Canon reduce cost of MRI scanner to one tenth
Monday, 11 January 2016   by www.electronicsweekly.com    
A transportable MRI machine to speed up the diagnosis and treatment of stroke patients
Wednesday, 22 April 2015   by medicalxpress.com    
Portable 'battlefield MRI' comes out of the lab
Thursday, 30 April 2015   by physicsworld.com    
Chemists develop MRI technique for peeking inside battery-like devices
Friday, 1 August 2014   by www.eurekalert.org    
New devices doubles down to detect and map brain signals
Monday, 23 July 2012   by scienceblog.com    
MRI Resources 
PACS - Safety pool - Safety Training - Devices - Blood Flow Imaging - Brain MRI
 
Boil off Rate
 
Rate of cryogen (liquid helium) evaporation in superconducting magnets, usually measured in liters of liquid per hour. The boil off rate of cryogen increases during ramping of the magnet and with eddy currents induced in the cryoshields by pulsed field gradients. In calculating cryogen consumption additional transfer and filling losses have to be considered.
See also Cryoshielding and Helium.

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• View the DATABASE results for 'Boil off Rate' (4).Open this link in a new window

 
Further Reading:
  Basics:
Cryogenic Liquids and their Hazards
   by www.ccohs.ca    
Zero Boil Off Cryostats
Friday, 23 September 2011   by www.cryogenicsociety.or    
  News & More:
A hot time for cold superconductors
Tuesday, 9 December 2003   by www.brightsurf.com    
Searchterm 'Superconducting Magnet' was also found in the following services: 
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Cryogen
 
A cooling agent, typically liquid helium or liquid nitrogen used to reduce the temperature of the magnet windings in a superconducting magnet. All cryogenic liquids are gases at normal temperatures and pressures. Different cryogens become liquids under different conditions of temperature and pressure, but all have two properties in common: they are extremely cold, and small amounts of liquid can expand into very large volumes of gas. The boiling points of cryogens are commonly below -150°C(- 238°F).
See also Helium.
Radiology-tip.comCryotherapy
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• View the DATABASE results for 'Cryogen' (55).Open this link in a new window


• View the NEWS results for 'Cryogen' (1).Open this link in a new window.
 
Further Reading:
  Basics:
Cryogenic Liquids and their Hazards
   by www.ccohs.ca    
  News & More:
A hot time for cold superconductors
Tuesday, 9 December 2003   by www.brightsurf.com    
New imaging and spectroscopy magnets eliminate liquid helium
Thursday, 29 August 2013   by www.spectroscopynow.com    
MRI Resources 
Hospitals - Spectroscopy pool - Bioinformatics - Education pool - MRI Technician and Technologist Schools - MRI Technician and Technologist Jobs
 
Cryomagnet
 
See Superconducting Magnet.

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Further Reading:
  News & More:
A hot time for cold superconductors
Tuesday, 9 December 2003   by www.brightsurf.com    
MRI Resources 
Spine MRI - Colonography - Services and Supplies - Homepages - Jobs pool - MRI Technician and Technologist Jobs
 
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