Radiometric Measurement of Time-Varying Temperature Profiles

Due to interest in non-invasive monitoring of subcutaneous temperature in hyperthermia treatments, a thermometer based on a multi-frequency microwave radiometer is compared to a standard invasive thermocouple system. The exprments have been made inside a phantom structure consisting of a three-layer box construction, a polyacrylamide-gel slab being sandwiched between two water layers. The uniformn temperatures of the external layers are separately controlled in time by thermostats in order to create a one-dimensional transient hyperthermia-like temperature profile inside the gel. A comparison among the data obtained by thermocouples and by a 4 channel radiometer, and the results from a theoretical model has shown good agreement. The transient temperature profile has been retrieved by means of a Kalman filtering of data. The agreement between the retrievals from radiometric and thermocouple data is satisfactory, the difference being about 1°C during the whole duration of treatment.