Thulium fiber laser lithotripsy using tapered fibers

Area of Science:

• Urology
• Laser Medicine
• Biomedical Engineering

Background:

• Thulium fiber laser (TFL) is an emerging alternative for laser lithotripsy.
• Conventional Holmium:YAG lasers have limitations in current lithotripsy procedures.
• Optimizing TFL delivery systems is crucial for effective stone fragmentation.

Purpose of the Study:

• To evaluate a novel short tapered fiber design for TFL lithotripsy.
• To assess the impact of beam expansion at the fiber tip on performance.
• To compare the tapered fiber with conventional fibers in terms of durability and efficacy.

Main Methods:

• TFL (1,908 nm, 10 Hz, 70 mJ, 1 ms) delivered via a tapered fiber (150- to 300-microm core) was tested ex vivo on uric acid and calcium oxalate monohydrate stones.
• Performance metrics included stone mass loss, crater depth, fiber transmission, burn-back, irrigation, and ureteroscope deflection.
• Tapered fiber results were compared against conventional small-core fibers.

Main Results:

• The tapered fiber demonstrated comparable stone ablation to conventional 100-microm fibers.
• No transmission losses or fiber burn-back were observed after 36,000 pulses with the tapered fiber.
• Conventional 150-microm fibers showed significant tip degradation after only 1,800 pulses.
• The tapered fiber maintained high irrigation rates and did not impede ureteroscope deflection.

Conclusions:

• A short tapered distal fiber tip effectively expands the TFL beam.
• This design significantly reduces fiber tip damage compared to conventional small-core fibers.
• The tapered fiber preserves lithotripsy efficacy, irrigation, and flexibility.