Inductive phase shift spectroscopy for volumetric brain edema detection: An experimental simulation

This study evaluates experimentally an induction based non-invasive technique for detection of changes of fluid volume through phase shift measurements as a possible method for volumetric brain edema monitoring. An induction coil spherical head model was build and tested. The model involves two different diameter coils coaxially centered on a twocompartment glass sphere head model centrally placed with respect to the coils. Three different fluid volumes of physiological saline in 20 ml increments were used to simulate different edema levels. Phase shift of the impedance coils as a function of relative fluid volume was measured at five frequencies (40, 50, 100, 200 and 300 MHz) by a commercial vector network analyzer. The results show significant phase shift increase as a function of frequency and fluid volume. The experiments with the coil- spherical head system suggest that the tested technique has the potential to become a practical configuration for non-invasive volumetric brain edema monitoring.