Fiber optic muzzle brake tip for reducing fiber burnback and stone retropulsion during thulium fiber laser lithotripsy

Abstract

The experimental thulium fiber laser (TFL) is being explored as an alternative to the current clinical gold standard Holmium:YAG laser for lithotripsy. The near single-mode TFL beam allows coupling of higher power into smaller optical fibers than the multimode Holmium laser beam profile, without proximal fiber tip degradation. A smaller fiber is desirable because it provides more space in the ureteroscope working channel for increased saline irrigation rates and allows maximum ureteroscope deflection. However, distal fiber tip burnback increases as fiber diameter decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback but increased stone retropulsion. A “fiber muzzle brake” was tested for reducing both fiber burnback and stone retropulsion by manipulating vapor bubble expansion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 ?? ? s , and 300 Hz using a 100 - ? m -core fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560 - ? m -outer-diameter, 360 - ? m -inner-diameter tube with a 275 - ? m -diameter through hole located 250 ?? ? m from the distal end. The fiber tip was recessed a distance of 500 ?? ? m . Stone phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed ex vivo. Small stones with a mass of 40 ± 4 ?? mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25 ± 4 ?? s

Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser

“…In 2005, the first report on Thulium fiber laser lithotripsy adapted a continuous-wave generator to operate in a pulsed mode and demonstrated the feasibility of lithotripsy on COM and UA stones [59]. Thereafter, fibers with a core diameter as small as 50-150 µm were repeatedly reported to efficiently deliver Thulium fiber laser beam on urinary stones [40,42,54,[60][61][62][63][64][65][66][67][68]. Also, cumulative evidence from a series of studies on distal fiber tip design suggests the muzzle tip design for prevention of stone retropulsion during Thulium fiber laser delivery [60,62,63,67,68].…”

“…Thereafter, fibers with a core diameter as small as 50–150 µm were repeatedly reported to efficiently deliver Thulium fiber laser beam on urinary stones [ 40 , 42 , 54 , 60 – 68 ]. Also, cumulative evidence from a series of studies on distal fiber tip design suggests the muzzle tip design for prevention of stone retropulsion during Thulium fiber laser delivery [ 60 , 62 , 63 , 67 , 68 ].…”

“…Also, cumulative evidence from a series of studies on distal fiber tip design suggests the muzzle tip design for prevention of stone retropulsion during Thulium fiber laser delivery [ 60 , 62 , 63 , 67 , 68 ].…”

Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

“…Both, fragmentation and propulsion processes, are highly influenced by the chosen laser parameters (pulse energy, pulse duration, repetition rate) [15,17,18]. The propulsion can be measured via a variety of methods, for example by evaluating the maximum deflection angle of a pendulum due to laser impact [18][19][20][21] or by analysing horizontal [9][10][11][12] or vertical stone movements [13] in terms of maximum stone displacement. The main disadvantage of these techniques is that the propulsion effect of only one single laser pulse can be evaluated.…”

Advances in Lasers for the Treatment of Stones—a Systematic Review

“…The other is a more peculiar development: a fiber optic muzzle brake tip made of stainless steel to apply on thulium laser fibers. Similar to muzzle brakes used in rifles and artillery canons to reduce recoil and redirect propellant gases sideways, this laser fiber muzzle brake not only reduces stone retropulsion by 85%, but also provides minimal fiber degradation and an efficient stone ablation [ 71 ].…”