Measuring water content of body equivalent materials using an RF resonant cavity

This thesis explores a resonant cavity perturbation technique to accurately measure infant body composition in the radio frequency regime. Infant body composition is an important marker of immediate and lifelong health; current methods for measuring infant body composition are expensive or unable to be performed frequently. A cost-effective screened enclosure was built to act as an RF resonant cavity designed to be sensitive to the changes in lean body mass of infants. The electric field interior to the cavity was measured using an Array Solutions VNA UHF, and a mathematical model was developed which showed the relationship between size, shape factor, and composition of a sample with the corresponding shifts in resonant properties. The system was validated using simple phantoms made of bovine lard and reverse osmosis water of known composition, shape, and volume. It was found that the shape and volume of the sample greatly affected the resonant properties. However, it was possible to accurately assess the composition of spherical containers of different sizes and compositions. We conclude that this technique may provide an accurate, noninvasive, and inexpensive measurement of body composition in infants.