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Result : Searchterm 'Radio Frequency' found in 12 terms [] and 63 definitions []
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Searchterm 'Radio Frequency' was also found in the following services: 
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News  (7)  Resources  (2)  Forum  (3)  
 
Absorbed Dose
 
This dose means the RF power absorbed per unit of mass of an object, and is measured in watts per kilogram (W/kg).
The absorbed dose is dependent on the duty cycle and transmitter-coil type and increases with field strength, radio frequency power and and body size.
The specific absorption rate (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.

See also Specific Absorption Rate, MRI Safety, and MRI Risks.
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Further Reading:
  Basics:
Commission delays electromagnetic fields legislation
Monday, 29 October 2007   by cordis.europa.eu:80    
Physics of MRI Safety
   by www.aapm.org    
  News & More:
SED Guidance
Saturday, 1 January 2022   by www.mriphysics.scot.nhs.uk    
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    
Evaluation of Absorbed Dose by MRI Read-Out
Saturday, 18 November 2017   by www.jstage.jst.go.jp    
Searchterm 'Radio Frequency' was also found in the following service: 
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Radiology  (2) Open this link in a new window
Amplifier
 
Hardware components from MRI systems. The radio frequency (RF) amplifier increases the power (measured in Watt) of the pulses from mW to kW and the gradient amplifier increases the power of the gradient pulses for the gradient coils.

See also Hardware.
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MRI Resources 
Safety Products - MRI Technician and Technologist Career - Liver Imaging - Journals - Distributors - Jobs
 
Cardiac PacemakerMRI Resource Directory:
 - Safety -
 
A pacemaker is a device for internal or external battery-operated cardiac pacing to overcome cardiac arrhythmias or heart block. All implanted electronic devices are susceptible to the electromagnetic fields used in magnetic resonance imaging. Therefore, the main magnetic field, the gradient field, and the radio frequency (RF) field are potential hazards for cardiac pacemaker patients.
The pacemaker's susceptibility to static field and its critical role in life support have warranted special consideration. The static magnetic field applies force to magnetic materials. This force and torque effects rise linearly with the field strength of the MRI machines. Both, RF fields and pulsed gradients can induce voltages in circuits or on the pacing lead, which will heat up the tissue around e.g. the lead tip, with a potential risk of thermal injury.
Regulations for pacemakers provide that they have to switch to the magnet mode in static magnetic fields above 1.0 mT. In MR imaging, the gradient and RF fields may mimic signals from the heart with inhibition or fast pacing of the heart. In the magnet mode, most of the current pacemakers will pace with a fix pulse rate because they do not accept the heartsignals. However, the state of an implanted pacemaker will be unpredictable inside a strong magnetic field. Transcutaneous controller adjustment of pacing rate is a feature of many units. Some achieve this control using switches activated by the external application of a magnet to open/close the switch. Others use rotation of an external magnet to turn internal controls. The fringe field around the MRI magnet can activate such switches or controls. Such activations are a safety risk.
Areas with fields higher than 0.5 mT (5 Gauss Limit) commonly have restricted access and/or are posted as a safety risk to persons with pacemakers.
mri safety guidance
MRI Safety Guidance
A Cardiac pacemaker is because the risks, under normal circumstances an absolute contraindication for MRI procedures.
Nevertheless, with special precaution the risks can be lowered. Reprogramming the pacemaker to an asynchronous mode with fix pacing rate or turning off will reduce the risk of fast pacing or inhibition. Reducing the SAR value reduces the potential MRI risks of heating. For MRI scans of the head and the lower extremities, tissue heating also seems to be a smaller problem. If a transmit receive coil is used to scan the head or the feet, the cardiac pacemaker is outside the sending coil and possible heating is very limited.
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Further Reading:
  Basics:
MRI in Patients with Implanted Devices: Current Controversies
Monday, 1 August 2016   by www.acc.org    
Magnetic resonance imaging in patients with cardiac pacemakers: era of MR Conditional designs
Thursday, 27 October 2011   by 7thspace.com    
  News & More:
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
BIOTRONIK debuts pacemaker with continuous MRI sensor
Wednesday, 30 August 2023   by www.medicaldevice-network.com    
Patients with standard pacemakers, ICDs may safely undergo MRIs
Friday, 24 February 2017   by www.cardiovascularbusiness.com    
ITOCHU Named the Exclusive Distributor for ViewRay's MRI-Guided Radiation Therapy System in Japan
Thursday, 22 January 2015   by www.prnewswire.com    
Modern Implantable Heart Devices Safe For Use In MRI Scans
Wednesday, 16 March 2005   by www.sciencedaily.com    
Searchterm 'Radio Frequency' was also found in the following services: 
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News  (7)  Resources  (2)  Forum  (3)  
 
Cardiac StentForum -
related threadsMRI Resource Directory:
 - Safety -
 
The MRI safety of cardiac stents is dependent of the material, the examined part of the body and the used field strength. A susceptibility artifact is expected also in low magnetic fields, but less.
mri safety guidance
MRI Safety Guidance
Most of the used materials are non-magnetic, for this case there is no risk for movement caused through the magnetic field. If the cardiac stent is outside the region of the radio frequency pulse, also the risk of e.g. heating is low.
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Further Reading:
  Basics:
Guidelines for the Management of Patients with Coronary Artery Stents Referred for MRI Procedures
Tuesday, 1 January 2019   by www.ismrm.org    
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Radiology  (2) Open this link in a new window
Carr Purcell Meiboom Gill SequenceInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(CPMG) This type of spin echo pulse sequence consisting of a 90° radio frequency pulse followed by an echo train induced by successive 180° pulses and is useful for measuring T2 weighted images. It is a modification of the Carr-Purcell RF pulse sequence, with 90° phase shift in the rotating frame of reference between the 90° pulse and the subsequent 180° pulses in order to reduce accumulating effects of imperfections in the 180° pulses. Suppression of effects of pulse error accumulation can alternatively be achieved by switching phases of the 180° pulses by 180°.
 
Images, Movies, Sliders:
 MRI - Anatomic Imaging of the Ankle 1  Open this link in a new window
    
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Further Reading:
  Basics:
Fast Spin Echo(.pdf)
Tuesday, 24 January 2006   by www.81bones.net    
Magnetic resonance imaging
   by www.scholarpedia.org    
  News & More:
Spin echoes, CPMG and T2 relaxation - Introductory NMR & MRI from Magritek
2013   by www.azom.com    
MRI Resources 
Abdominal Imaging - Jobs - Movies - Software - MRI Centers - Education pool
 
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