CT-guided microwave liver tumors ablation and automatic adjustment of frequency
Tags : fuzzylogic, hepatocellularcarcinoma, microwaves, radiatedenergy, radiofrequencyablation, radiology
Category : Original articles
Authors : Bouaoud Souad, Bouharati Imane, Bouharati KhaoulaFull text (PDF file)
Objective. Primary tumors such as hepatocellular carcinoma (CC) treated by the use of microwaves has the advantage in its ability to overcome the large heat sinks inherent in this vascular organ. Also, it offers the possibility of treating larger tumors with fewer applicator placements in less time compared to radiofrequency ablation techniques. However, the transmission of electromagnetic energy is determined by the dielectric permittivity of biological tissues. This one is very complex to model because it is a function of frequency, temperature and other factors specific to the tissues. Add to this, much of the energy radiated by antennas is in absorbed by biological tissue in areas near the antenna and cannot propagate as a plane wave. In this case, the penetration depth calculations take into account the attenuation of the tissue. In this study, we propose the use of a 3D radiological image of the carcinoma for the geometric calculation of its center mass. This image should also provide the spatial distribution of density across the tumor.
Methods. The introduction of the scano-guided probe makes it possible to reach its location with great precision. From the distribution of the tissue density, the parameters characterizing the thermal properties are calculated. An automatic system regulates the frequency (radiated energy) and the time which will then be adjusted during the operation according to the pre-set parameters.
Results. The predefined norms relating to the nature of the tissue, the propagation of the temperature through the volume, the necessary time, with a heating frequency prefixed, that leads to the cellular destruction are introduced in algorithm. During the process of tumor destruction, the thermal conductivity varies. This variation is taken into account in the output of the system which acts on the readjustment of temperature and the regulation of time.
Conclusion. This tool offers the benefit of accuracy, overheating, optimization of tissue conduction and heat loss. Existing models are based on approximations in electromagnetic-thermal interaction estimates. We propose to introduce in the frequency and time adjustment calculation software, a fuzzy logic system that supports these uncertainties inherent to the complexity of the tissue to be treated.