V03-02: First Clinical Study on SuperPulse Thulium Fiber laser for Lithotripsy
Ho:YAG laser wavelength of 2.1 µm is off the peak of water absorption and the efficiency of stone fragmentation can be improved by using a laser with wavelength matching peak water absorption at 1.94 µm, where water absorbs 4.5 times more efficiently than at 2.1 µm. Previous in vitro studies have shown that thulium (Tm) fiber laser operating at wavelength 1.94 µm can be effective for stone fragmentation. Recently, we have evaluated in vitro performance of Super-Pulse Tm fiber laser prototype and found its efficiency to be higher than the leading Ho:YAG laser for fragmentation (x1.7 times) and dusting (x2.3 to 4 times) for equal energy and rep rate settings. This is pilot clinical evaluation of the first commercially available Super-Pulse Tm fiber laser system for lithotripsy.
The Super-Pulse Tm fiber laser device has been cleared for clinical use by the Ministry of Health of Russian Federation and the protocol has been approved by the institutional Ethical Review committee. We prospectively analyzed 40 patients who underwent Super-Pulse Tm fiber laser lithotripsy for renal (n=29), ureteral (n=9), and bladder stones (n=2) with various laser settings. Size of the stone, its density, operation time, “laser on” time were measured. Based on surgeon’s feedback, retropulsion and intraoperative visibility were assessed. Post–operative parameters were recorded.
For renal stones, the average size was 15.6 mm ( 5.5 – 27 mm), for ureteral stones – 9.6 mm (5 – 13 mm), for bladder stones – 28 mm (15 – 42 mm). The average stone density for renal stones was 1217 HU (524 – 2053 HU), for ureteral stones - 1262.2 HU (700 – 1782 HU), for bladder stones – 839.5 HU (779 – 900 HU). The average time to complete renal stone fragmentation (to dust or small fragments and their washing out) was 30.2 min (10 – 50 min), for ureteral stones – 19.2 min (10 – 28 min), for bladder stones – 23 min (21 – 25 min). The retropulsion during miniPCNL and URS in the vast majority of cases was insignificant especially when using dusting mode with energy level less than 0.5 J. Visibility was estimated as optimal by surgeons in most cases. Fragmentation mode with energy level 2 to 6 J and repetition rate 5-10 Hz was most suitable for bladder stone disintegration.
Our preliminary data indicate high efficiency and safety of the novel Super-Pulse Tm fiber laser lithotripter with wavelength 1.94 µm for urinary stone disintegration. Wide range of settings (0.05 to 6 J; 5 to 2000 Hz) available for this laser allows efficient destruction of stones of any composition and location in both dusting and fragmentations modes. Further studies will confirm those results.