Magnetic Field Dosimetry - Biophysical and Clinical Aspects

Abstract

Electromagnetic field (EMF) dosimetry has been developed by two parallel but interacting and complimentary streams: theoretical and experimental. Theoretical dosimetry deals with simplified models, while experimental dosimetry concerns the development of methods and instruments suitable for measuring and calculating physical quantities of EMF energy that is imparted to an absorbing body, such as characteristics of internal fields, specific absorption rate (SAR) or related variables1’2 The basic theoretical dosimetry is well developed for homogeneous objects, while dosimetric models for inhomogeneous systems (such as living tissues) need considerable work. The absorption and distribution of electromagnetic energy in the human body is a very complex phenomenon that depends on the mass, shape and size of the target, the orientation of this target with respect to the field vector, the electrical properties of both the body and the environment. Other variables that may play a substantial role in possible biological effects are those that characterize the environment (e.g. ambient temperature, relative humidity and body insulation) and those that characterize the individual (age, sex, physiological state, activity level, disease, etc.) Such information is essential for assessing therapeutic effectiveness of electromagnetic signals and for extracting diagnostic information from the observed field effects. The exact knowledge of coupling between the source of EMF and the target/model tissue can be extremely helpful in engineering for the optimization of the shape and size of applicators.