Fiber Bragg Grating Sensors-Based Assessment of Laser Ablation on Pancreas at 808 and 1064 nm Using a Diffusing Applicator: Experimental and Numerical Study

Laser ablation (LA) holds great promise for the localized treatment of pancreatic tumors. However, there are still many technical aspects that require improvements before largely applying this technique in clinical practice. This work shed light on the following subjects: the thermal response of the pancreas to LA using a diffusing applicator and delivering different laser wavelengths (i.e., 808 and 1064 nm); the development of a pancreas-specific numerical model with temperature-dependent tissue properties based on non-Fourier heat conduction for predicting the temperature distribution. To experimentally study the pancreas thermal response and to tune the model parameters, 80 fiber Bragg grating (FBG) sensors, embedded in arrays with millimetric spatial resolution, were implanted in ex vivo pancreas undergoing LA to obtain the real-time and 2-D temperature distribution. Based on the temperature measured by the FBG sensors, results show that the laser wavelength affects the pancreas thermal response: at 2 mm from the applicator, LA at 808 nm resulted in a thermally affected area 5%-15% larger than at 1064 nm, whereas no notable difference was observed at 6 mm. The temperature distribution and laser-induced lesion obtained from the non-Fourier numerical model were found to closely match the experimental results when the phase lag of the temperature gradient was five times that of the heat flux vector.