A Temperature-Controlled Laser Hot Needle With Grating Sensor for Liver Tissue Tract Ablation

In this article, we proposed a laser hot needle for liver tissue tract ablation. The proposed laser hot needle is powered by a 4500-nm-diode laser incorporated with a closed-loop control system that comprises of a uniform fiber Bragg grating (FBG) temperature sensor and a computer. Based on the real-time feedback input from the FBG temperature sensor, the laser power is regulated by a proportional–integral–derivative (PID) control system to control the needle temperature. In the characterization test, a chirped grating-based distributed temperature sensor is employed for measuring the tissue temperature profile in the ex vivo bovine liver tissue during the ablation. A histological test is conducted to study the impact of tract ablation to the cellular structures of treated tissue and tissue coagulation. In a tract ablation test, a ~50-mm $\times \sim 6$ -mm (length $\times $ width) thermal denaturation zone has been created on ex vivo bovine liver tissue with the laser hot needle at 150 °C.