Laser-induced Thermotherapy (LITT): Dose-Effect Relation on Lung Tissue

Abstract

Summary Laser-induced thermotherapy (LITT) is an established minimally invasive technique which has been proven to be successful for many years, especially in the treatment of liver metastases. The lung is the organ most affected by metastases, next to the liver. Many patients do not meet the criteria of inclusion for metastasectomy which is considered the gold standard (3, 4). LITT could be a safe and effective alternative for these inoperable patients. In case of bilateral lung disease, segmental excision or lobectomy can be complemented by LITT of solitary focuses in other lobes. For a successful therapy management of lung metastases, lesion sizes are required for creating situations comparable to RO excision. For this purpose, the dose-effect relation between the applied Nd:YAG laser power and the coagulation size attainable was investigated for a clinically established applicator system. The tests were made ex vivo on porcine lungs using a LITT puncture set for open surgery. The laser power ranging from 20 to 32 watts was applied to the tissue through an internally cooled diffusor-tip applicator. The induced coagulation lesions were measured for volumes and maximum extensions. While the tested LITT system proved to be suitable for application with powers up to 32 watts, its maximum efficacy had been reached already at 25 watts and an exposure time of 20 minutes. Higher powers did not generate substantially larger lesions, but caused a temperature holdup and subsequent carbonisation. The data on the dose-effect relation obtained by this study contribute essentially to clinical application and lay the ground for a safe and validated therapy control.