Endovascular laser treatment. Comparison of lasers and fibers of different generations: study of temperatures and tissue damage produced on a porcine liver model

The current international guidelines identify tumescent ablative techniques such as laser thermal ablation (EVLA) and radiofrequency (RFA) to be the gold standard in varicose vein surgery. New-generation lasers have been introduced, which have high wavelengths (1940 and 2000 nm) and therefore with a greater affinity for water than the old generation (980- and 1470-nm lasers). The purpose of the study was to evaluate the biological effect and the temperatures produced during the use of lasers with different wavelengths (980, 1470, and 1940 nm) and with optical fibers with different emission (radial diverging at 60° and radial with cylindrical mono-ring) on in vitro model. Porcine liver was used as an in vitro model. The laser control units used had 3 different wavelengths: 980, 1470, and 1940 nm. The optical fibers used were 2: the Corona 360 fiber (mono-ring radial fiber) and the infinite fiber (cylindrical mono-ring fiber). The laser operating parameters used included the delivery of 6 W in continuous wave (CW) mode with a standard 10 s/cm pull-back. Eleven measurements were made for each fiber and for each laser, for a total of 66 measurements. We performed measurements of the maximum transverse diameter produced with laser irradiation to evaluate the biological effectiveness of the treatment. During laser irradiation, we performed measurements of both of the temperatures reached on the external surface of the porcine tissue, near the tip of the laser catheter, and the temperatures reached inside the irradiated tissue by using a digital laser infrared thermometer with apposite probe. The calculation of the statistical significance ( p -value) was obtained with the ANOVA method with two between factors. The comparison study of the maximum transverse diameter (DTM) of the lesion produced on the target tissue demonstrated the absence of statistically significant differences between the 1470-nm laser and the 1940-nm laser regardless of the type of fiber used. It was not possible to perform measurements of the maximum transverse diameter produced with the 980-nm laser as this produced no visible effect on the model. The comparison study of the temperatures developed during and immediately after the treatment instead showed higher maximum surface temperatures (TSM) and a higher thermal increase (IT) regardless of the type of fiber used in a statistically significant way (respectively, p 0.002 and 0.012) when using the 980-nm laser versus the 1940-nm laser. Comparing instead the 980-nm laser with 1470 nm, there were no differences in TI recorded during the procedure but a significantly higher VTI ( p 0.029). The experiment conducted with the new generation laser, compared with those of the first and second generation, shows how this works overall at lower temperatures with the same effectiveness.