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Result : Searchterm 'high field' found in 1 term [] and 35 definitions []
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Searchterm 'high field' was also found in the following services: 
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News  (60)  Resources  (13)  Forum  (11)  
 
RELAX 0.35T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.isoltech.co.kr/english/product/035t.htm From ISOL Technology
'RELAX is open type MRI system created by making up for the weakness of existing conventional MR systems and applying the strength and the application of the middle to high field MR without uncompromising the image quality.
RELAX offers you a premium mix of form, performance and functionality that are patient and user friendly beyond comparison. - New breed of MRI pursuing - patients comfort'
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Open
Head, C-spine, L-spine, TMJ, Knee, Shoulder, General purpose, Phased Array System: 4 digital receiver channels (Up to 12 channels)
SYNCHRONIZATION
ECG/peripheral: Optional/yes, respiratory gating
PULSE SEQUENCES
2D/3D Spin echo, 2D/3D Gradient echo, 2D/3D Fast spin echo, Inversion recovery, 2D/3D Fast gradient echo sequences, FLAIR/STIR, 2D/3D TOF
IMAGING MODES
3D volume imaging (MIP, MPR) MR Angiography package
30 cm
MAGNET TYPE
Permanent
40 cm diameter (patient)
MAGNET WEIGHT
13500 kg
H*W*D
170 x 210 x 130 cm
COOLING SYSTEM TYPE
Water-cooled coil and air-cooled amplifier
STRENGTH
25 - 30 mT/m
5-GAUSS FRINGE FIELD
lower than 2.4 m from the iso-center
Passive and active
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MRI Resources 
MRI Centers - Knee MRI - Implant and Prosthesis pool - Jobs pool - Abdominal Imaging - Movies
 
Shady ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Shady artifact
DESCRIPTION
Localized inhomogeneous brightness
REASON
Various causes
HELP
Check the correct positioning, call the service
Uneven intensity or brightness may occasionally be noted on high field MRI e.g. of the brain. There are various causes of localized inhomogeneous brightness across the MRI images such as improper tuning of the RF transceiver, unbalanced deposition of the RF energy due to incorrect geometry and localized attenuation due to positioning or anatomical variants.
mri safety guidance
Image Guidance
Tuning of the RF transceiver, a homogeneity correction filter and better positioning of the scanned object and/or coil in the scanner.
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MRI Resources 
Directories - Cochlear Implant - Guidance - Absorption and Emission - Non-English - MRI Centers
 
Specific Absorption Rate
 
(SAR) The Specific Absorption Rate is defined as the RF power absorbed per unit of mass of an object, and is measured in watts per kilogram (W/kg).
The SAR describes the potential for heating of the patient's tissue due to the application of the RF energy necessary to produce the MR signal. Inhomogeneity of the RF field leads to a local exposure where most of the absorbed energy is applied to one body region rather than the entire person, leading to the concept of a local SAR. Hot spots may occur in the exposed tissue, to avoid or at least minimize effects of such theoretical complications, the frequency and the power of the radio frequency irradiation should be kept at the lowest possible level. Averaging over the whole body leads to the global SAR.
It increases with field strength, radio frequency power and duty cycle, transmitter-coil type and body size. The doubling of the field strength from 1.5 Tesla (1.5T) to 3 Tesla (3T) leads to a quadrupling of SAR. In high and ultrahigh fields, some of the multiple echo, multiple-slice pulse sequences may create a higher SAR than recommended by the agencies. SAR can be reduced by lower flip angle and longer repetition times, which could potentially affect image contrast.
Normally no threatening increase in temperature could be shown. Even in high magnetic fields, the local temperature increases not more than 1°C. 2.1°C is the highest measured increase in skin temperature. Eddy currents may heat up implants and thus may cause local heating.

FDA SAR limits:
Whole body: 4W/kg/15-minute exposure averaged;
Head: 3W/kg/10-minute exposure averaged;
Head or torso: 8W/kg/5 minute exposure per gram of tissue;
Extremities: 12W/kg/5 minute exposure per gram of tissue.

IEC (International Electrotechnical Commission) SAR limits of some European countries:
All limits are averaged over 6 minutes.
Level 0 (normal operating mode): Whole body 2W/kg; Head 3.2W/kg; Head or Torso (local) 10W/kg; Extremities (local) 20W/kg;
Level I (first level controlled operating mode): Whole body 4W/kg; Head 3.2W/kg; Head or Torso (local) 10W/kg; Extremities (local) 20W/kg;
Level II (second level controlled operating mode): All values are over Level I values.
(For more details: IEC 60601-2-33 (2002))

In most countries standard MRI systems are limited to a maximum SAR of 4 W/kg, so most scanning in level II is impossible.
For Level I, in addition to routine monitoring, particular caution must be exercised for patients who are sensitive to temperature increases or to RF energy.
For Japan different SAR limits are valid.
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• View the DATABASE results for 'Specific Absorption Rate' (8).Open this link in a new window


• View the NEWS results for 'Specific Absorption Rate' (1).Open this link in a new window.
 
Further Reading:
  Basics:
SED Guidance
Saturday, 1 January 2022   by www.mriphysics.scot.nhs.uk    
On the estimation of the worst-case implant-induced RF-heating in multi-channel MRI.
Thursday, 2 March 2017   by www.ncbi.nlm.nih.gov    
What MRI Sequences Produce the Highest Specific Absorption Rate (SAR), and Is There Something We Should Be Doing to Reduce the SAR During Standard Examinations?
Thursday, 16 April 2015   by www.ajronline.org    
Evaluation of Specific Absorption Rate as a Dosimeter of MRI-Related Implant Heating
2004   by www.imrser.org    
  News & More:
Specific Absorption Rate and Specific Energy Dose: Comparison of 1.5-T versus 3.0-T Fetal MRI
Tuesday, 7 April 2020   by pubs.rsna.org    
MRI in Patients with Implanted Devices: Current Controversies
Monday, 1 August 2016   by www.acc.org    
Commission delays electromagnetic fields legislation
Monday, 29 October 2007   by cordis.europa.eu:80    
Accounting for biological aggregation in heating and imaging of magnetic nanoparticles
Tuesday, 2 September 2014   by www.ecnmag.com    
Guidance for Industry and FDA Staff, Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices
Monday, 14 July 2003   by www.fda.gov    
Searchterm 'high field' was also found in the following services: 
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News  (60)  Resources  (13)  Forum  (11)  
 
Transmit Receive CoilInfoSheet: - Coils - 
Intro, 
Overview, 
etc.MRI Resource Directory:
 - Coils -
 
(T/R) Also called transceiver coil. An RF coil that acts as a transmitter (T) producing the B1 excitation field and as a receiver (R) of the MRI signal. Such a coil requires a T/R switching circuit to switch between the two modes. A body coil is typically a T/R coil, but smaller volume T/R coils (head/extremities) are often used at high field as a possibility of reducing RF power absorption (SAR).
 
Images, Movies, Sliders:
 MRI of the Skull Base  Open this link in a new window
    
SlidersSliders Overview

 Anatomic Imaging of the Orbita  Open this link in a new window
      

 
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• View the DATABASE results for 'Transmit Receive Coil' (4).Open this link in a new window

 
Further Reading:
  Basics:
System Architecture
2003   by www.revisemri.com    
Electrical eddy currents in the human body: MRI scans and medical implants
   by www.phy.olemiss.edu    
MRI Resources 
Implant and Prosthesis - MRI Technician and Technologist Career - Portals - Patient Information - MRA - Non-English
 
Ultra™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
medical.toshiba.com/clinical/radiology/ultra.htm From Toshiba America Medical Systems Inc.;
the Ultra™ system was developed to help healthcare providers be more competitive by delivering greater patient comfort and a broad range of clinical capabilities, says Anita Bowler, product manager, MRI Business Unit, Toshiba America Medical Systems Inc With its unique, powerful gradient technology, the Ultra™ performs advanced clinical studies and consistently provides high-resolution images that are typically associated with high field MRI systems. At the same time, the Ultra™ offers a truly open feeling that makes patients more relaxed, especially those with claustrophobic tendencies.
Device Information and Specification
CLINICAL APPLICATION
Whole Body
CONFIGURATION
Quadrature, solenoid and multi-channel configurations
PULSE SEQUENCES
SE, FE, IR, FastSE, FastIR, FastFLAIR, Fast STIR, FastFE, FASE, Hybrid EPI, Multi Shot EPI, Single shot EPI diffusion, True SSFP, SuperFASE; Angiography: 2D(gate/non-gate)/3D TOF, SORS-STC, Black Blood MRA
POWER REQUIREMENTS
380/400/415/440/480 V
COOLING SYSTEM TYPE
Cryogenless
STRENGTH
25 mT/m
Passive, active
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MRI Resources 
Directories - Nerve Stimulator - Jobs pool - MRI Technician and Technologist Schools - Journals - Health
 
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