Circular and magnetron inductor/sensor coils to detect volumetric brain edema by inductive phase shift spectroscopy: A sensitivity simulation study

Circular and planar magnetron coils were evaluated and compared for their ability to detect edema in the brain through volumetric inductive phase shift spectroscopy. The circular coil was considered as a single turn wire and the magnetron surface coil configuration was based on the principle of the cavity magnetron with successive slots. The brain cavity was modeled as an idealized sphere transversely centered with respect to the coils. The volumetric sensitivity to changes in the brain was examined by inserting in the brain cavity a spherical hematoma. The magnetic flux densities generated by the inductor and magnetron coils were evaluated through a three-dimensional finite elements solution of the quasi-static equations. Spectra of inductive phase shift induced in a second circular or magnetron receiver coils were estimated in a range of frequencies from 100KHz to 50MHz. In the analyzed range, the sensitivity of the phase shift to the presence of the edema increased with frequency. Using a planar magnetron as an induction coil increased somewhat the sensitivity to volumetric phase shift detection of edema over the use of a circular coil. The use of a planar magnetron as the receiver coil produced a substantial increase in sensitivity, in particular at the higher frequency of 50 MHz.