Ablation efficiency and thermal damage of infrared lasers on ex vivo lamb brain tissues

The objective of this investigation is to guide to select the most su􏰆fficient infrared laser for the neurosurgery. For this reason, 1940-nm thulium 􏰄fiber laser, 1470- nm diode laser, 1070-nm ytterbium 􏰄fiber laser and 980-nm diode laser were operated with the ex vivo lamb brain tissues. Combination of some parameters such as brain tissue (subcortical and cortical tissues), laser output power, energy density, mode of operation (continuous and pulsed-modulated modes) and exposure time were applied. Pre-dosimetry study was conducted to determine coagulation and carbonization onset times for the lamb brain tissues. In this way, safe operation zone could be described for the dosimetry study. In the dosimetry study, both tissues were exposed to some energy densities (2J-4J) and power levels which are 200mW-400mW-600mW-800 mW and 0.5W-1W-1.5W-2W for 1940-nm and 1470-nm laser applications, respectively. The last two laser emitted light to both brain tissues with some power levels (1W- 2W-3W-4W) and energy densities (20J-40J). After each laser application, coagulation and ablation diameters were calculated under a light microscope. It was aimed to fi􏰄nd suitable laser parameter so as to perform the greatest ablation effi􏰆ciency which is determined as ablation diameter over coagulated diameter. Consequently, 1940-nm and 1470-nm lasers created ablated and coagulated areas while the other two lasers made only coagulated areas. Ablation e􏰆fficiencies were calculated for 1940-nm and 1470-nm lasers. It was found that the former and the latter can be used as a subcortical and cortical tissue ablator, respectively.