New visualization strategy to study the dynamics of surgical coagulation devices in biological tissue using absolute subsurface thermal imaging

Visualisation of the thermo dynamics of surgical coagulation devices like laser, diathermy and RFA devices in tissue are essential to get better understanding about the principles of operation of these devices. Thermo cameras have the ability to measure absolute temperatures. However, the visualization of temperature fields using thermal imaging has always been limited to the surface of a medium. We have developed a new strategy to look below the surface of biological tissue by viewing through a ZincSelenide window positioned alongside a block of tissue. When exposed from above with an energy source, the temperature distribution below the surface can be observed through the window. To obtain a close-up view, the thermo camera is enhanced with special macro optics. The thermo dynamics during tissue interaction of various electro surgery modes was studied in biological tissues to obtain a better understanding of the working mechanism. Simultaneously with thermal imaging, normal close-up video footage was obtained to support the interpretation of the thermal imaging. For comparison, temperature gradients were imaged inside a transparent tissue model using color Schlieren imaging. The new subsurface thermal imaging method gives a better understanding of interaction of thermal energy of surgical devices and contributes to the safety and the optimal settings for various medical applications. However, the technique has some limitations that have to be considered. The three imaging modalities showed to be both compatible and complementary showing the pro- and cons- of each modality.