Thermal ablation techniques like radiofrequency or laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs. Minimal access, parenchymal preservation, and a low complication rate render them suitable for pulmonary tumors as well. Their successful clinical application depends on the induction of sufficiently large lesions and a knowledge of the energy parameters required for complete thermal ablation. The aim of this study was to establish a dose-response relationship for a percutaneous and an intraoperative system for LITT of lung tissue. Thermal lesions were induced in healthy porcine lungs using an Nd:YAG laser (1,064 nm). LITT was performed with a percutaneous application system in group I (n = 18) and an intraoperative application system in group II (n = 90). Laser energy was applied for 600-1,200 s in a power range of 20-32 W (12,000-38,400 J). The lesions were longitudinally and transversally measured, and the volume was calculated after the intervention. Furthermore, an open application system was used to perform LITT under in vivo conditions during lung perfusion and ventilation in domestic pigs. Lesion volumes in both groups showed a plateau-like curve when the laser power increased from an initial level of 25 W. With the percutaneous puncture system (group I), the application of 28 W (16,800 J) for 10 min generated the largest lesions with a volume of 12.54 +/- 1.33 cm(3), an axial diameter of 39.33 +/- 2.52 mm, and a diametrical diameter of 24.67 +/- 1.15 mm. A longer application time was not possible due to thermal instability of the applicator. Moreover, group I started developing extensive carbonizations at a laser power of 22 W (13,200 J). The intraoperative application system (group II) achieved the largest lesion volumes of 11.03 +/- 2.54 cm(3) with diameters of 34.6 +/- 4.22 mm (axial) and 25.6 +/- 2.51 mm (diametrical) by an exposure time of 20 min and a power of 32 W (38,400 J). Here extensive carbonizations only started to occur at 28 W (33,600 J). Under in vivo conditions, all pigs tolerated the LITT procedure well without complications. Besides a typical cooling effect in the vicinity of blood vessels, the thermal lesions were about three times smaller than the ex vivo lesions. Both the percutaneous and the open LITT application system induced reproducible, clinically relevant lung lesions. The percutaneous puncture set generated large relevant lesions, although its usability is limited by its restricted capacity and high carbonization risk. It is suitable for powers up to 22 W. The intraoperative application system allows higher energy exposure to induce larger lesion volumes. This study elucidates the dose-effect relation of two clinically relevant puncture sets.

The laser is a well established surgical instrument in lung therapy. This report provides information on the biophysical basics of the laser-induced thermotherapy (LITT) of lung metastases. Optical properties like absorption and scattering determine the penetration depth of laser radiation in tissue. These parameters vary dynamically during the application and define in combination with thermal tissue properties the achievable destruction volume. Parenchyma behaves very differently compared to more dense tissues due to local inhomogenities and the large amount cavaties filled with air. Beside an account of the affecting parameters an overview of therapy options is given. Therapeutic results depend not only on the tissue properties but also on the technical equipment, e.g. the applicator design and the energy applied. Complex dosimetric models allow for a calculation of the lesion's size in advance.

No abstract

In surgical practice we are often confronted with ethically challenging situations when treating patients not capable of expressing their own wishes. Issues of futile treatment by indicating operations arise particularly with regard to severe dementia. The concept of futility describes forms of therapy which are not appropriate to improve the patient's condition, but for application in clinical practice the concept is insufficiently defined.In ethically challenging situations, e.g. in the treatment of severely demented patients, we need to balance the medical condition and prognosis with the documented or assumed wishes of the patients. Involving the relatives competently is essential. The indication for surgery in patients with severe dementia, for example, needs to be individualized striving for optimal care, a clear communication about treatment goals with the relatives and preventing distress and burnout for staff. Co-operation with specialists in medical ethics is recommended.