Fichera, L., Pardo, D., Illiano, P., Ortiz, J., Caldwell, D., Mattos, L.
Published in The International Journal of Medical Robotics and Computer Assisted Surgery, March 2015
DOI 10.1002/rcs.1656

Abstract:
Background: The use of lasers in transoral surgery enables precise tissue incision with minimal adverse effects for surrounding and underlying structures. Nonetheless, the lack of haptic feedback during laser cutting impairs the surgeon's perception of the laser incision depth, potentially leading to undesired tissue damage.
Methods: In this paper we present a system for the estimation of incision depth during Transoral Laser Microsurgery (TLM). The system allows clinicians to monitor the incision depth during laser cutting. The estimation is based on a forward model, mapping a set of inputs (laser parameters) to an incision depth. In this work we consider typical inputs employed by surgeons during TLM (i.e., power, scanning frequency, energy delivery mode, incision length and laser exposure time). Experiments to understand the influence of the different inputs on the resulting incision depth were performed. User trials were conducted to verify the effectiveness of the system in supporting the execution of precise laser incision.
Results: The validity of the models of depth of incision was verified on ex-vivo tissue (chicken breast), revealing an error (RMSE) of 0.1mm over depths ranging up to 1.4mm. Results of user trials indicate that on-line estimation of depth significantly improves the incision depth control of inexperienced users.
Conclusions: On-line estimation of laser incision depth can be achieved using a function that maps the laser inputs to the resulting ablation depth. This estimation method can be readily applied to surgical any laser source. Providing depth estimation during the execution of a laser incision allows inexperienced users to perform precise tissue cutting, thus presenting a potential application for the training of laser surgeons.