RF Safety

2005 ◽  
pp. 283-300 ◽  
Keyword(s):  
Rf Safety

Improved MR Thermometry to Measure Brain Temperatures

2008 ◽  
Author(s):  
Devashish Shrivastava ◽  
Lance DelaBarre ◽  
Timothy Hanson ◽  
J. Thomas Vaughan
Keyword(s):  
High Field ◽  
Core Body Temperature ◽  
Temperature Response ◽  
Time History ◽  
Rf Heating ◽  
Mr Thermometry ◽  
Ultra High Field ◽  
High Fields ◽  
Rf Safety

An MR thermometry technique with sub-degree celsius accuracy is needed to measure in vivo temperatures vs. time in porcine brains at ultra-high fields. Porcine models are used to study thermoregulatory temperature response of the ultra-high field radiofrequency (RF) heating. The porcine hot critical temperature limit is comparable to and lower than that of humans. Also, porcine thermoregulatory mechanisms are similar to humans. Thus, conservative porcine thermoregulatory temperature responses can help develop new RF safety thresholds for ultra-high field human MRI. Sub-degree C temperature accuracy is needed since RF safety guidelines limit the maximum in vivo head temperature change due to RF heating to 1 °C over the core body temperature. Three-dimensional temperature maps over time are required since non-uniform RF power deposition at ultra-high fields and blood flow produce non-uniform in vivo temperatures with local hot spots. Thermogenic hazards are related to in vivo temperatures and temperature-time history — and not to the typically measured whole head average specific absorption rate.

scholarly journals Reduction of Specific Absorption Rate using Carbon foam Inside Enclosures

2020 ◽  
Vol 9 (3) ◽  
pp. 1684-1688
Keyword(s):  
Mobile Phone ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Carbon Foam ◽  
Uniform Mesh ◽  
Specific Absorption ◽  
Quarter Wavelength ◽  
Novel Method ◽  
Rf Safety

The interaction of a mobile antenna and a passenger is analyzed inside a metallic enclosure. The specific absorption rate (SAR) of the passenger in the elevator using a mobile phone is calculated. A standardized model of human head is filled with liquid that simulates the RF absorption characteristics. The non-uniform mesh technique in frequency domain is employed to obtain 1g SAR [Specific Absorption Rate] and other important parameters. The mobile phone is modeled as a quarter wavelength Planar Inverted F Antenna (PIFA), and it is of .01m from the head. PIFA is operated at frequencies of 900 and 1800MHz with transmitting power .3 W . It is observed that the values of SAR inside the metallic enclosure exceeds the RF safety limits. Therefore, this project proposes a novel method to reduce the SAR by using carbon foam which absorbs microwave radiation. Simulated results have evidenced the efficiency of the proposed technique of SAR reduction inside the enclosures.

scholarly journals RF safety of wires in interventional MRI: Using a safety index

2001 ◽  
Vol 47 (1) ◽  
pp. 187-193 ◽  
Author(s):  
Christopher J. Yeung ◽  
Robert C. Susil ◽  
Ergin Atalar
Keyword(s):  
Interventional Mri ◽  
Safety Index ◽  
Rf Safety
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