Granulation and tumor regrowth in the area of bronchi stent implants may result in restenosis. It had been shown that by means of Thulium-Fibre-Laser (TFL) a controlled ablation and reduction of the tissue within the stent could be performed. When using Nd:YAG irradiation there is risk for explosive flames, burns of fibre and stent, ruptures of stent meshes as well as perforation of stent and cover. Therefore it was the aim to investigate the safety margin when using TFL.
Four different types of clinical used stents (with/without cover) were fixed to pig trachea tissue. Irradiation was performed by fibre assisted TFL-1940nm-laser irradiation while laser power, light application duration and distance, as well as oxygen percentage and contamination were varied.
In case of Nitinol-stents rupture were observed at power levels ≥7W or distances of <5mm, oxygen conc. of 40% result in increased flame appearance. Polyurethan-covers were ruptured at each variable, flame appeared at 5W. Silicon-stents were destroyed at power levels of about 5W and distances of <5mm and additionally 30%-oxygen or contamination either by blood or soot result in increased appearance of burns and flames.
Based upon these observations in clinical TFL-irradiation the distance should ≥5 mm and the power level should be ≤6W. Furthermore the oxygen conc. should not exceed 30% and short term continuous irradiation of less than 15s exposition should be considered. In case of Silicon-stents light application on contaminated area should be avoided.
Ronald Sroka, Johannes Frank, Frank Reichenberger, J. Behr, and Wolfgang Gesierich, "Investigation on the potential of thulium-fibre-laser irradiation for in-stent tissue ablation (Conference Presentation)," Proc. SPIE 10041, Optical Techniques in Pulmonary Medicine II, 100410L (Presented at SPIE BiOS: January 29, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254985.5369908510001.
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