Temperature measurement during laser brain ablation by thulium fiber laser

Abstract

The aim of the study was to find a relationship between laser power, exposure time, ablation efficiency and temperature increase during laser brain ablation by Thulium fiber laser. The thermal effects of the 1940-nm Tm-fiber laser on the brain tissue was also investigated in terms of ablation efficiency. These experiments are very important in order to model temperature increase-ablation efficiency during lasing with different power and exposure time. 4-5 mm coronal sections were taken from lamb brains. Laser was applied at cortical and subcortical tissue with 0-0.1 mm distance, in both continuous and pulsed modes with 400 mW and 600 mW which were chosen by a predosimetric study. In continuous and pulse mode doses were changed with exposure time and on-off cycle respectively, in order to achive the tissue to absorb same energy. During lasing temperature increases were recorded by a thermoprobe (thermoprobe is a system which a 300 micrometer fiber was embedded into a thermocouple). The radius of ablation and coagulation for each laser application was recorded by a microscope. By calculating ablation efficiency (100xablation/calculation radius) the appropriate laser doses were determined for both cortical and subcortical tissue. The maximum ablation efficiency for cortical and subcortical tissue in both continous and pulsed mode was found for 600 mW. Ablation efficiencies for continuous mode was superior than the pulsed mode for all laser doses which were studied. Temperature increases showed a significant differences for continuous and pulse mode operating systems and effect the ablation efficiencies.