**3. Noninvasive temperature monitoring**

Noninvasive temperature monitoring of hyperthermia cancer treatment is one of the crucial points for its successful clinical applications. MRI is often discussed to be a prospective solution to this problem. However, it is a costly way (commercially available hyperthermia system controlled by MRI has a price above 1 million EUR).

Because of that, cheaper solutions-based on, e.g., microwave or ultrasound technology, could be a convenient alternative to MRI temperature monitoring. Till now, microwave radiometers have been discussed for this purpose. Radiometers can measure the absolute value of temperature, but their spatial resolution is not sufficient. They integrate thermal noise from certain volumes, and thus, they indicate approximately average temperature inside this volume, so it may happen that the microwave radiometer will not identify existing hot spots or cold spots.

Our theoretical and experimental research work is focused now on microwave differential tomography (MDT). The Department of Biomedical Technology (the Czech Technical University in Prague) developed its own MDT system (see photo in **Figure 4**) in cooperation with Prof. Andrea Massa from Eledia Research Center (Trento, Italy). It seems realistic that the MDT methods can be used for 3D noninvasive temperature monitoring of the treated volume during thermotherapy in oncology. Existing suitable reconstruction algorithms, which allow quasi-real-time monitoring of changes of dielectric properties due to changes of temperature, were implemented. Reconstruction algorithms were tested on different 2D and 3D models. The obtained results using the Distorted Born Algorithm (DBA) and Born Algorithm (BA) were compared in terms of the algorithms' ability to reconstruct the shape and position of the target and flatness of the obtained object function in regions without change in dielectric properties.
