A Miniaturized, 1.9F Integrated Optical Fiber and Stone Basket for Use in Thulium Fiber Laser Lithotripsy

The thulium fiber laser (TFL) is being explored as an alternative laser lithotripter to the standard holmium:yttrium-aluminum-garnet laser. The more uniform beam profile of the TFL enables higher power transmission through smaller fibers. In this study, a 100-m core, 140-m outer-diameter (OD) silica fiber with 5-mm length hollow steel tip was integrated with 1.3F (0.433-mm OD) nitinol wire basket to form a 1.9F (0.633-mm OD) device. TFL energy of 30mJ, 500s pulse duration, and 500Hz pulse rate was delivered to human uric acid stones, ex vivo. Stone ablation rates measured 1.5 +/- 0.2mg/s, comparable to 1.7 +/- 0.3mg/s using bare fiber tips separately with stone basket. With further development, this device may minimize stone retropulsion, allowing more efficient TFL lithotripsy at higher pulse rates. It may also provide increased flexibility, higher saline irrigation rates through the ureteroscope working channel, reduce fiber degradation compared with separate fiber and basket manipulation, and reduce laser-induced nitinol wire damage.