Radiometric temperature reading of a hot ellipsoidal object inside the oral cavity by a shielded microwave antenna put flush to the cheek

Abstract

A new scheme for detection of vesicoureteral reflux (VUR) in children has recently been proposed in the literature. The idea is to warm bladder urine via microwave exposure to at least fever temperatures and observe potential urine reflux from the bladder back to the kidney(s) by medical radiometry. As a preliminary step toward realization of this detection device, we present non-invasive temperature monitoring by use of microwave radiometry in adults to observe temperature dynamics in vivo of a water-filled balloon placed within the oral cavity. The relevance of the approach with respect to detection of VUR in children is motivated by comparing the oral cavity and cheek tissue with axial CT images of young children in the bladder region. Both anatomical locations reveal a triple-layered tissue structure consisting of skin–fat–muscle with a total thickness of about 8–10 mm. In order to mimic variations in urine temperature, the target balloon was flushed with water coupled to a heat exchanger, that was moved between water baths of different temperatures, to induce measurable temperature gradients. The applied radiometer has a center frequency of 3.5 GHz and provides a sensitivity (accuracy) of 0.03 °C for a data acquisition time of 2 s. Three different scenarios were tested and included observation through the cheek tissue with and without an intervening water bolus compartment present. In all cases, radiometric readings observed over a time span of 900 s were shown to be highly correlated (R ~ 0.93) with in situ temperatures obtained by fiberoptic probes.

A recently proposed scheme for detection of vesicoureteral reflux (VUR) in children is based on combined warming of bladder urine and temperature reading by medical radiometry of potential urine reflux from the bladder back into the kidneys. The relevance and limitations of this approach with respect to detection of VUR are motivated by comparing anatomical characteristics of the oral cavity and cheek tissue (as a test bed) based on CT images of young children in the bladder region. In order to mimic variations in reflux urine temperature within the bladder, a target water balloon placed in the oral cavity was flushed with water. Three different scenarios were tested and included radiometric observation through the cheek tissue with and without an intervening water bolus compartment present. In all cases, radiometric readings were shown to be highly correlated with in situ temperatures obtained by fiberoptic probes