The Effect of Conventional Ho:YAG, Magneto Ho:YAG and Thulium Fiber Laser on Soft Tissue: An Ex Vivo Comparative Study in Porcine Kidney

<b>Background/Objectives</b>: In an attempt to combine the benefits of the Holmium:YAG (Ho:YAG) laser and Thulium Fiber Laser (TFL), the "Magneto" mode lowers the peak power of the Ho:YAG laser, generating longer duration pulses. The purpose of this study is to compare the effect of the standard virtual basket (VB) Ho:YAG laser, Magneto Ho:YAG laser and TFL on soft tissue in an ex vivo model. <b>Methods</b>: Two renal units from a female pig were used for the current experiment. Sixteen distinct areas were defined. Each area included three parallel lines, which were made with the three different laser technologies. The VB Ho:YAG laser was used for the first line and the Ho:YAG laser in the "Magneto mode" was used to generate the second line, while the third line was performed with a TFL in short pulse mode. The same laser settings (1 J/10 Hz/10 W) and the same fiber diameter (200 μm) were used for all three laser incisions. The same surgeon performed all incisions with a standardized and repeatable technique, controlling hand speed and distance of laser fiber from kidney surface using the stabilization setup. Sections of the selected areas produced distinct paraffin blocks, each one containing three parallel laser lines. Two independent pathologists evaluated the incision depth, incision width, coagulation depth and carbonization effect of the three different lasers. <b>Results</b>: Although the incision depth and the carbonization effect were comparable between the three lasers, incision width and coagulation depth showed a statistically significant difference. Median incision width was 1.17 (1.04, 1.99) mm for the VB Ho:YAG laser, 1.05 (0.89, 1.50) mm for the Magneto Ho:YAG laser and 0.82 (0.65, 0.88) mm for the TFL (<i>p</i> = 0.001). The coagulation depth was 0.49 (0.41, 0.56) mm for the VB Ho:YAG laser, 0.51 (0.39, 0.59) mm for the Magneto Ho:YAG laser and 0.18 (0.17, 0.23) mm for the TFL (<i>p</i> < 0.001). During post hoc analysis for the three comparisons, the differences between the VB Ho:YAG laser and TFL and between the Magneto Ho:YAG laser and TFL were statistically significant for both parameters. <b>Conclusions</b>: Both the VB and Magneto Ho:YAG lasers produced laser incisions with statistically significant greater incision width and coagulation depth than the TFL on the ex vivo model. Overall, the Magneto Ho:YAG laser was associated with the greatest median coagulation depth. Post Hoc Man-Whitney tests for the three comparisons revealed statistically significant differences only between the VB Ho:YAG laser and TFL and between the Magneto Ho:YAG laser and TFL. This finding could potentially be translated into better haemostasis during endourological soft tissue surgery. The implementation of additional studies, both experimental and clinical ones, is of outmost importance to draw safer conclusions.