Authors
Iskra S, McKenzie R, Cosic I. Monte Carlo simulations of the electric field close to the body in realistic environments for application in personal radiofrequency dosimetry. Radiat Prot Dosimetry. Jan 17, 2011. Ahead of print.

Background
To measure exposure to radiation, body-worn dosimeters have long been used to provide real-time data of personalized exposure to RF field strengths in actual or realistic environments. These measurements can be correlated with the actual time and place they occurred to provide a measure of exposure over a nominated period of time. As body intercepts and thus perturbs the incident field, dosimeter measurements depend on the orientation of the body with respect to the field. It is important to take this uncertainty into account when measuring body exposure to radiation.

Objective of the study
To use a Monte Carlo approach in conjunction with the finite difference time domain method (FDTD) to obtain distributions of the electric field close to a human body model in simulated, realistic environments.

Methods
A set of basic FDTD solutions are obtained for single, unit magnitude, plane waves propagating towards the body at incident angles. To simulate realistic environments, values are assigned to the plane wave parameters depending on their statistical distribution. Two NORMAN-based human body models were used: an adult and a child. The name NORMAN derives from NORMalised MAN and is meant to represent the anatomy and size of an average or reference adult man.

Results
The mean response for the dual dosimeter configuration differs slightly from the single dosimeter. However, the spread in values is significantly lower for the dual dosimeter compared with the single dosimeter configuration. An underestimation of the incident field strength occurs when the field is incident, for instance, towards the rear of the body and the dosimeter is mounted on the front of the torso. It also occurs at electrically small distances from the surface where the reflected wave destructively interferes with the incident field.

Conclusion
The results of simulations provide a basis for determining correction factors that can be applied to measurements obtained from body-worn dosimeters.


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