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Result : Searchterm 'Gradient Coil' found in 2 terms [] and 20 definitions []
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Gradient CoilForum -
related threadsInfoSheet: - Coils - 
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Current carrying coils designed to produce a desired magnetic field gradient (so that the magnetic field will be stronger in some locations than others).
Proper design of the size and configuration of the coils is necessary to produce a controlled and uniform gradient. Three paired orthogonal current-carrying coils located within the magnet that are designed to produce desired gradient magnetic fields, which collectively and sequentially are superimposed on the main magnetic field (B0) so that selective spatial excitation of the imaging volume can occur.
Gradients are also used to apply reversal pulses in some fast imaging techniques. Gradient coils in general vary the main magnetic field, so that each signal can be related to an exact location. The gradient coil configuration for the z-axis consists of e.g., Helmholtz pair coils, and of paired saddle coils for the x- and y-axis.

See also the related poll result: 'Most outages of your scanning system are caused by failure of'
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• Related Searches:
    • Paired Saddle Coil
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    • Radio Frequency Coil
    • Acoustic Noise
    • Gradient Amplifier
 
Further Reading:
  Basics:
Electrical eddy currents in the human body: MRI scans and medical implants
   by www.phy.olemiss.edu    
HEAD AND NECK MRI GRADIENT COIL DESIGN
Thursday, 26 August 1999   by www.imaging.robarts.ca    
MRI Resources 
Directories - - Cardiovascular Imaging - Movies - Corporations - Used and Refurbished MRI Equipment
 
Shielded Gradient CoilsInfoSheet: - Coils - 
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Current-carrying gradient coils with reduced gradient fringe field inside of the magnet cryostat structures like cryoshields and He-vessel. The shielding can be accomplished by secondary actively driven coils or by passive screens, which are inductively coupled to the gradient coils. In both cases eddy currents outside of the gradient system will be reduced.

See also Eddy Currents.
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• View the DATABASE results for 'Shielded Gradient Coils' (4).Open this link in a new window

 
Further Reading:
  Basics:
Faraday's Law
   by hyperphysics.phy-astr.gsu.edu    
MRI Resources 
Guidance - Sequences - Shielding - Diffusion Weighted Imaging - MR Myelography - Mobile MRI
 
DeviceForum -
related threadsInfoSheet: - Devices -
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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:
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 Medical-Ultrasound-Imaging.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.comradGamma Camera,  Linear Accelerator
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Medical-Ultrasound-Imaging.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:
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small-steps-can-yield-big-energy-savings-and-cut-emissions-mris
Thursday, 27 April 2023   by www.itnonline.com    
Portable MRI can detect brain abnormalities at bedside
Tuesday, 8 September 2020   by news.yale.edu    
Point-of-Care MRI Secures FDA 510(k) Clearance
Thursday, 30 April 2020   by www.diagnosticimaging.com    
World's First Portable MRI Cleared by FDA
Monday, 17 February 2020   by www.medgadget.com    
Low Power MRI Helps Image Lungs, Brings Costs Down
Thursday, 10 October 2019   by www.medgadget.com    
Cheap, portable scanners could transform brain imaging. But how will scientists deliver the data?
Tuesday, 16 April 2019   by www.sciencemag.org    
The world's strongest MRI machines are pushing human imaging to new limits
Wednesday, 31 October 2018   by www.nature.com    
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    
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Acoustic Noise
 
Vibrations of the gradient coil support structure create sound waves. These are caused by the interactions of the magnetic field created by pulses of the current through the gradient coil with the main magnetic field in a manner similar to a loudspeaker coil. The sounds made by the scanner vary in volume and tone with the type of procedure being performed.
Sound pressure is reported on a logarithmic scale called sound-pressure level, expressed in decibel (dB) referenced to the weakest audible 1 000 Hz sound pressure of 2 * 10-5 pascal (20 micropascal). Sound level meters contain filters that simulate the ear's frequency response. The most commonly used filter provides what is called 'A' weighting, with the letter 'A' appended to the dB units, i.e. dBA.
MRI system noise levels increase with field strength. Disposable earplugs and/or headphones for the patient are recommended in high-field systems. Noise-canceling systems and special earphones are available, and active acoustic control systems were developed, e.g. softtone, pianissimo. A sequence with low noise gradient pulses is also called 'whisper sequence'.

See also Phon and Decibel.
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• View the DATABASE results for 'Acoustic Noise' (9).Open this link in a new window

 
Further Reading:
  Basics:
MRI Noise in Utero Not Harmful for Baby's Ears
Tuesday, 28 September 2010   by www.medgadget.com    
  News & More:
Noise from Magnetic Resonance Imaging Can Have Short-Term Impact on Hearing
Thursday, 22 February 2018   by www.diagnosticimaging.com    
Echo Planar Imaging at 4 Tesla With Minimum Acoustic Noise(.pdf)
   by www.bnl.gov    
TOSHIBA SHOWCASES PATIENT-FRIENDLY 3T MR SYSTEM
Sunday, 29 November 2009   by medical.toshiba.com    
MRI Resources 
Lung Imaging - Corporations - Software - Stimulator pool - Diffusion Weighted Imaging - MRCP
 
CoilForum -
related threadsInfoSheet: - Coils - 
Intro, 
Overview, 
etc.MRI Resource Directory:
 - Coils -
 
A coil consists of one or more loops of conductive wire, looped around the core of the coil. Coils are part of the hardware of MRI machines and are used to create a magnetic field or to detect a changing magnetic field by voltage induced in the wire. A coil is usually a physically small antenna.
The perfect coil produces a uniform magnetic field without significant radiation.
Different types of MRI coils are used in MR systems:
Gradient coils are used to produce controlled variations in the main magnetic field (B0) to provide spatial localization of the signals and to apply reversal pulses in some imaging techniques.
MR imaging radio frequency coils to receive and/or transmit the RF signal.
Shim coils provide auxiliary magnetic fields in order to compensate for inhomogeneities in the main magnetic field of the MRI machine.

See also Gradient Coil, Radio Frequency Coil, Hardware and Coil Loading.

See also the related POLL result: '3rd party coils are better than the original manufacturer coils'
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• View the DATABASE results for 'Coil' (193).Open this link in a new window


• View the NEWS results for 'Coil' (11).Open this link in a new window.
 
Further Reading:
  News & More:
3T MRI-Compatible Small Body Array Gets FDA Nod
Monday, 15 January 2024   by www.diagnosticimaging.com    
High-field MRI Coils – that work, superbly, even at 750 MHz
   by www.dotynmr.com    
New superconducting coil improves MRI performance
Wednesday, 20 July 2016   by www.eurekalert.org    
First European fully superconductive coil reaching a magnetic field of 25 Tesla produced
Wednesday, 8 June 2016   by www.news-medical.net    
ScanMed Introduces a Groundbreaking New Orbit and Mandible Array to the MRI Market
Wednesday, 26 March 2014   by www.digitaljournal.com    
MRI coil optimized for imaging of infants gets FDA clearance
Tuesday, 17 April 2012   by www.medcitynews.com    
Low-profile MRI coil company inching toward commercialization
Wednesday, 21 December 2011   by www.medcitynews.com    
High-Resolution Uniform MR Imaging of Finger Joints Using a Dedicated RF Coil at 3 Tesla
Sunday, 31 January 2010   by www.ncbi.nlm.nih.gov    
DOTmed Industry Sector Report: MRI Coil Sales & Service Companies
Thursday, 13 December 2007   by www.dotmed.com    
MRI Resources 
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