Introduction: Previous benchtop studies have shown that optimal stone ablation with the thulium fiber laser (TFL) is achieved with short pulse and maximum peak power. Furthermore, in vitro TFL studies have also demonstrated that at equivalent power, the combination of higher energy and lower frequency offers the most efficient dusting settings. Holmium based benchtop studies have shown that low pulse energy produces small fragments while high pulse energy produces larger fragments.[1] No such studies have been performed with the TFL platform, and thus with this study we aim to assess the quality and size of fragments produced at different pulse energies. [1] Sea J, Jonat LM, Chew BH, Qiu J, Wang B, Hoopman J, Milner T, Teichman JM. Optimal power settings for Holmium:YAG lithotripsy. J Urol. 2012 Mar;187(3):914-9. doi: 10.1016/j.juro.2011.10.147. Epub 2012 Jan 20. PMID: 22264464. Methods: All tests were conducted using an IPG Photonics TLR-50W TFL system and a 200µm fiber on “soft” (5:2) Begostone 6mm x 6mm (H x D) phantoms. We tested six different pulse energies (0.05J, 0.1J, 0.2J, 0.4J, 0.5J, and 1J) at varying frequencies to produce either 10W or 20W of power. Our previous benchtop studies have shown that short pulse provides superior ablation, so all pulse profiles were adjusted to maximum peak power and short pulse. The laser fiber was advanced beyond the distal end of a flexible ureteroscope (Dornier AXISTM, 3.6 F working channel) and the stone phantoms were treated in a test tube filled with water and immersed in a water bath at room temperature (Figure 1). Continuous dusting was performed for 1 minute with the 10W settings, and 30 seconds with the 20W settings. Each pulse energy was tested three times with three different stone phantoms. Resultant fragments were sieved, dried for 24 hours and examined under the microscope. Results: At all tested pulse energies, no stone phantoms were broken into large fragments. All stone materials were pulverized into small dust. When examined under the microscope, individual dust particles were smaller than 20µm for all the tested settings (Figure 1). Exact measurements were not obtained and deemed not clinically relevant. Conclusions: Unlike Holmium lithotripsy where higher pulse energy results in larger fragments, in Thulium lithotripsy higher pulse energy did not result in increased fragment size. SOURCE OF Funding: N/A
