Thulium fiber laser shows efficiency advantage in experimental setting

Results of an in vitro study evaluating the ablative effects of lasers for endocorporeal lithotripsy indicate that a super-pulsed thulium fiber laser (TFL) has greater efficiency than a holmium:YAG (Ho:YAG) laser, even when using the TFL with a smaller core-diameter fiber (CDF), reported Frédéric Panthier, MD, at the 2020 European Association of Urology Virtual Congress.¹

The study compared a 50 W TFL (IPG Photonics) and a 30W MH1 Ho:YAG laser (Rocamed) for ablating hard and soft stone phantoms. Ablation rates (mm3/min) for the TFL were determined for its fine dusting (0.15 J/100 Hz), dusting (0.5 J/30 Hz), and fragmentation (1 J/15 Hz) modes and using both a 150 μm and 272 μm CDF (Sureflex). The Ho:YAG laser was equipped with a 272 μm CDF (Sureflex) and tested in dusting (0.5 J/30 Hz) and fragmentation (1 J/15 Hz) modes. Average power was 15 watts for all settings.

“Our results showed that with equal settings and laser fibers, in vitro ablation rates were twofold higher with the TFL than the Ho:YAG laser in fragmentation mode and fourfold higher for dusting,” said Panthier, department of Urology, Hôpital Tenon, Sorbonne Université, Paris, France.

“Most interesting, the ablation rate was still at least 50% higher using the TFL with the 150 μm CDF compared to the Ho:YAG laser with the 272 μm CDF.”

The experiments were done using immerged cubes of calcium oxalate monohydrate for the hard stones and uric acid for the soft stones. The setup included a spiral trajectory jointly controlled in contact mode with the stones and a laser activation time of 30 seconds. After drying of the stones, ablation volume was measured using three-dimensional scanning and segmentation.

In experiments with the hard stones where both lasers were equipped with a 272 μm CDF, the ablation rate was fourfold higher using the TFL compared with the Ho:YAG laser in dusting mode and twofold higher with the TFL compared with the Ho:YAG laser in fragmentation mode.For soft stones and with use of the 272 μm CDFs, the ablation volume was threefold higher for the TFL in dusting mode and twofold higher in fragmentation mode when compared with the Ho:YAG laser. All of the differences favoring the TFL were statistically significant.

Comparisons of the performance of the TFL using the 150 μm and 272 μm CDFs showed that across all 3 of its modes and for both stone types, the 272 μm CDF was associated with a significantly higher ablation rate than the 150 μm CDF except in fine dusting against soft stones (P = .28).

The TFL with the 150 μm CDF was associated with a significantly higher ablation rate than the Ho:YAG laser with the 272 μm CDF for dusting of hard and soft stones and fragmentation of hard stones, but not for fragmentation of soft stones (P = .12). Compared to the Ho:YAG laser with the 272 μm CDF in dusting mode, the TFL in fine dusting mode was associated with a twofold higher ablation rate using the 150 μm CDF and a threefold higher ablation rate using the 272 μm CDF.

Panthier has no potential conflict of interest to report.

Reference

1. Panthier F , Doizi S, Berthe L, et al. In vitro comparison of ablation rates between superpulsed thulium fiber laser and ho:YAG laser for endocorporeal lithotripsy. 2020 European Association of Urology Virtual Congress. July 17-26, 2020. Abstract PT131.

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