Temperature monitoring and lesion volume estimation during double-applicator laser-induced thermotherapy in ex vivo swine pancreas: a preliminary study

Tissue temperature distribution plays a crucial role in the outcome of laser-induced thermotherapy (LITT),a technique employed for neoplasias removal. Since recent studies proposed LITT for pancreatic tumors treatment, assessmentof temperature and of its effects around the laserapplicator could be useful to define optimal laser settings.The aims of this work are temperature monitoring and measurement of ablated tissue volume in an ex vivo porcinepancreas undergoing double-applicator LITT. A threedimensional numerical model is implemented to predict temperaturerise and volumes of ablated tissue in treated pancreas.Experiments are performed to validate the model, withtwo modalities: (1) 12-fiber Bragg grating sensors areadopted to monitor the heating and cooling during LITT at several distances from the applicators tip, and (2) 1.5-T MR imaging is used to estimate the ablated volume. Experimental data agree with theoretical ones: at 2 mm from both applicatorstips, the maximum temperature increase is approximately60 °C downward from the tips, while it increases of about40 °C and 30 °C, respectively, at the level and upward from the tips. This behavior occurs also at other distances, provingthat the tissue downward from the tip is mostly heated. Furthermore, the estimated volume with MRI agrees with theoretical one (i.d., 0.91±0.09 vs. 0.95 cm3). The encouraging results indicate that the model could be a suitable tool to choose the optimal laser settings, in order to control thevolume of ablated tissue.