| Summary: | Many of the current techniques of body composition assessment are either unsuitable for seriously ill patients or lacking precision. The disparity in electrical properties of fat and lean tissue suggests that the interaction between an alternating electromagnetic field and the human body could be a new potentially useful way to determine body composition. The purpose of the work described in this thesis was to develop an inexpensive, simple and safe non-invasive electrical technique of body composition assessment. A large coil, carrying an alternating current, produces an electromagnetic field within its volume. When a subject is placed inside the coil, the field configuration is disturbed and a corresponding change in the electrical behaviour of the coil can be observed. A theoretical analysis based on a helical waveguide model has allowed succesful prediction of the electrical behaviour of the coil when empty and also when it contains a simple homogeneous cylindrical phantom. A prototype helical waveguide system has been constructed, and the measured electric and magnetic field distributions in the coil compared with the theoretical predictions. The ability of the technique to discriminate between simple phantoms with electrical conductivities typical of muscle and of adipose tissue and between phantoms of the same conductivity but different volume has been confirmed experimentally. The suitability of the helical waveguide system for the determination of body composition <i>in vivo</i> has been assessed in a clinical trial involving 45 normal healthy volunteers (22 male, 23 female) ranging in age from 17 to 71 and in weight from 44 to 104 kg. Good correlations were found between changes in the electrical behaviour of the coil and fat-free mass predicted by three accepted techniques of body composition analysis.
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