Two-dimensional temperature feedback control strategy for thermal ablation of biological tissue

During thermal ablative procedures, the control of the thermal doses delivered to the target area is an essential factor for inducing the required thermal effect while preventing undesired damage to the surrounding healthy tissue. In this study, we propose a two-dimensional temperature control strategy exerted through millimeter-scale temperature measurements during superficial laser ablation (LA) of ex vivo porcine hepatic tissue. A theoretical model was developed as a pre-planning tool to accurately predict the laser-induced temperature increase during the controlled ablation, the temperature evolution, the two-dimensional thermal distribution, and attained tissue injury after superficial ablation. The temperature increase in the target area was controlled based upon the selection of biologically relevant temperature thresholds, i.e., 43 °C and 55 °C, and the maintenance of these thermal values at specific distances from the center of the laser beam. The experimental outcomes well validated the implemented theoretical model (e.g., a maximum difference of predicted and measured extension of superficial thermal damage of ~0.5 mm). Therefore, the model resulted well suited for evaluating the pre-treatment setting parameters of the control strategy and designing the optimal characteristics of the sensing system. The attained results demonstrate the efficacy of the two-dimensional LA strategy to ensure the confinement of the desired temperatures within the selected region.