Peak Specific Absorption Rate Values Research Articles

Electromagnetic energy exposure of simulated users of portable cellular telephones

Describes a method to quantify the RF exposure of the users of portable cellular phones in terms of specific absorption rate (SAR). The method involves a robotic system to accurately position an isotropic E-field probe within equivalent biological tissue. The user of cellular phones is simulated by a simple human model (a phantom) consisting of a thin shell of fibreglass filled with a liquid having the complex dielectric constant of human brain tissue. The authors present the results of the dosimetric assays conducted using current and previous models of cellular telephones. The peak SAR values detected using the measurement method described are below the limits recommended by the National Council for Radiation Protection and Measurements (NCRP) Report 86 for the protection of humans exposed to RF electromagnetic energy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Heating pattern of helical microwave intracavitary oesophageal applicator

Helical microwave intracavitary oesophageal (HMIO) applicators were designed to operate at frequencies of 433 MHz and 915 MHz. Heating patterns were studied within muscle-equivalent phantom by thermographic camera and fibreoptic thermometers. The results showed that frequency significantly influenced the microwave heating pattern. The 433 MHz applicator had a single power deposition region, the longitudinal specific absorption rate (SAR) distribution appeared to be nearly even, and the maximum SAR value occurred close to the centre of the active length of the applicator. The 915 MHz applicator had two power deposition regions, the peak SAR values occurred at about 1/4 and 3/4 of the active length respectively. The radial SAR distribution suggested that there is no obvious difference between the 433 MHz and 915 MHz applicators in that the average radial penetration of 50% surface SAR (RP50) was about 0.65 cm. It was also shown that power deposition was axially symmetric for both 433 MHz and 915 MHz HMIO applicators. It is shown that better impedance matching is more important for intracavitary hyperthermia than for external hyperthermia. Choosing HMIO applicators in clinical practice is also discussed.

Average SAR and SAR Distributions in Man Exposed to 450-MHz Radiofrequency Radiation

Fifth-scale phantom models were exposed to 2450-MHz electromagnetic fields to obtain the average specific absorption rate (SAR) and SAR distribution in man exposed to 1 mW/cm/sup 2/ 450-MHz radiofrequency radiation for various polarizations and body positions. The average SAR was measured calorimetrically and SAR distribution was determined thermographically using an interactive computer system, The mean SAR, as averaged over the body, remained relatively constant at 0.050 W/kg, with a standard deviation of +-0.007 W/kg for all polarizations and body postures considered in the study. Peak SAR values were as high as 0.650 W/kg, occuring typicaly in the wrist.