A numerical method for imaging of biological microstructures by VHF waves

Imaging techniques give a fundamental support to medical diagnostics during the pathology discovery as well as for the characterization of bio-medical structures. The imaging methods involve electromagnetic waves in a frequency range that spans from some Hz to GHz and over. Most of these methods involve ionizing waves and scanning of a large human body area even if only a focused inspection is needed. In this paper, a numerical method to evaluate the shape of microstructures for application in the medical field, with a very low invasiveness for the human body, is proposed. In particular, the tooth's root canal is considered. In fact, this is one of the hot topics in the endodontic procedures where rotary instruments are widely used. These instruments are subjected to sudden mechanical damage during the surgical process, due to cyclic fatigue directly related to the canal's geometrical characteristics. In order to develop an improved endodontic procedure so that instrument breakage probability and canal milling precision are optimized, preliminary canal root reconstruction techniques have to be implemented. These techniques are usually based on invasive X-ray imaging. Thus, a minimally invasive, easy to use imaging technique that can be applied many times on the patient is of great interest. To this aim, a method based on a flexible thin-wire antenna radiating non ionizing VHF waves is proposed. By measuring the spatial magnetic field distribution in the neighboring area, it is possible to reconstruct the microstructure image by estimating the shape of the antenna against a sensor panel. The mathematical model is strictly non-linear and the inverse problem described above is solved numerically; first simulation results are presented in order to show the validity and the robustness of the proposed approach. (C) 2013 Elsevier B.V. All rights reserved.