Holmium, thulium lasers show similar ablative effect on stones

The high-power holmium (HPH) laser with Moses technology (Lumenis Moses Pulse 120H) and the super-pulse thulium fiber laser (SPTF) have a similar ablative effect when operated at the same power, but when evaluated at maximal dusting settings, the SPTF laser seems to hold an advantage for greater efficiency, according to research reported at the AUA annual meeting in Chicago.

Researchers compared the ablative effects of the two laser systems in an in vitro study using calcium oxalate monohydrate-like artificial stones and a prototype of the SPTF laser.

“Innovations in lithotripsy technologies continue to emerge. The Moses technology was developed to enhance the HPH laser lithotripter, but more recently it is being challenged by the novel SPTF laser that features a more optimal wavelength with a higher water absorption, lower pulse energy, and higher pulse rate (frequency),” said first author Laurian B. Dragos, MD, consultant urologist at Victor Babes¸ University of Medicine and Pharmacy, Timis¸oara, Romania.

“Our study shows that the SPTF laser might increase the efficiency of laser lithotripsy, therefore decreasing operative time. Still, we need to consider that these are in vitro findings, and our study did not assess other aspects of laser lithotripsy such as retropulsion, visibility, and size of the resulting stone fragments (dust). Further clinical evaluations are required.”

The in vitro study analyzed ablation volumes created in calcium oxalate monohydrate-like artificial stones using the two laser systems. The HPH laser was equipped with a 230-micron core-diameter fiber, and the SPTF laser, which was a prototype device, had a 200-micron core-diameter fiber. The SPTF laser can use fibers as small as 50 microns.

Each laser was used in several different experimental setups that used a variety of settings for power, energy, and frequency and distances of 0, 1, and 2 mm between the laser fiber and the stone. For each combination of settings, the tests with the HPH laser were done in both close and distance modes. Time of laser activation was 10 seconds in all experiments.

Ablation volume was measured using a 3-D high-precision computer-controlled micro-scanner.

Continue to the next page for more.For both laser systems, ablation volume increased with increasing laser power and decreased as the distance between the fiber and the stone increased. Results achieved using the HPH Moses technology laser in distance and close modes showed that if power, energy, and frequency were kept constant, ablation volume was consistently greater when the laser was operated in distance mode. The differences between the two modes, however, were not statistically significant.

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The ablation volumes achieved using the SPTF laser were similar to those achieved using the HPH Moses technology laser in distance mode when the two devices were operated with the same power and pulse energy settings. The two technologies also resulted in similar ablation volumes when they were operated with the same power and the HPH Moses technology was used in close mode with a very low pulse energy and very high frequency.

At each laser’s best capabilities for dusting settings that used the lowest pulse energy and highest frequency (HPH: 0.2 J and 80 Hz; SPTF: 0.05 J and 900 Hz), the ablation volume was almost threefold greater for the SPTF laser than for the HPH Moses technology laser. At stone distances of 0 mm and 1 mm, mean ablation volume was 1.28 mm² and 0.68 mm², respectively, for the SPTF laser; 0.42 mm² and 0.21 mm², respectively, for the HPH laser in close mode; and 0.48 mm² and 0.29 mm², respectively, for the HPH laser in distance mode.