Fiber-optic chirped FBG for distributed thermal monitoring of ex-vivo radiofrequency ablation of liver.

Daniele Tosi,Edoardo Gino Macchi,Elfed Lewis,Gabriel Leen,Sandro Rossi,Giovanni Braschi,Mario Gallati,Alfredo Cigada

doi:10.1364/boe.5.001799

Abstract

A linearly chirped fiber Bragg grating (LCFBG) has been used as a temperature sensor for online monitoring of radiofrequency thermal ablation (RFTA). The LCFBG acts as a distributed sensor, with spatial resolution of 75 μm. A white-light setup that records the LCFBG spectrum estimates the temperature profile in real time. Three RFTA experiments have been performed ex-vivo on porcine liver measuring the radial temperature distribution during the heating process. The analysis of thermal maps quantifies the spatial heat distribution along the measurement axis and determines the ablation efficiency.

Highlights

Thermal ablation (TA) is one of the main therapies for the treatment of tumors, up to 3-5 cm in size [1]; TA is commonly applied in hepatic, lung, kidney, prostatic tumor treatment, as well as in other medical applications
The measurement has been performed ex-vivo on porcine liver, which is the preferred phantom of human liver; porcine liver provides a good match with human liver in terms of consistency of the biological tissue, as well as electrical impedance throughout the heating process
The linearly chirped fiber Bragg grating (LCFBG) sensor has been connected with the sensing tip in contact with the radiofrequency thermal ablation (RFTA) needle and attached to the base of the chamber; the positioning is shown in Fig. 5(a) where the whole length of the LCFBG has been illuminated by red light

Summary

Introduction

Thermal ablation (TA) is one of the main therapies for the treatment of tumors, up to 3-5 cm in size [1]; TA is commonly applied in hepatic, lung, kidney, prostatic tumor treatment, as well as in other medical applications. We introduce the possibility of using a linearly chirped FBG (LCFBG) [17,18] to provide a distributed thermal monitoring along the fiber axis; the possibility of achieving distributed sensing in a short active length with hundreds of sensing points is a significant improvement in thermal dosimetry measurement over FBGs that usually record up to 5 sensing points within the ablation region. In this application, the LCFBG acts as a distributed reflector, in which the spectral reflectivity is tied to the spatial distribution according to a linear match. Three different experimental setups are used, measuring the thermal distribution during the RFTA heating until the high-impedance condition

Setup and temperature sensitivity

Results and discussion

Conclusions