Fiber-optic manipulation of urinary stone phantoms using holmium:YAG and thulium fiber lasers

Abstract

Abstract. Fiber-optic attraction of urinary stones during laser lithotripsy may be exploited to manipulate stone fragments inside the urinary tract without mechanical grasping tools, saving the urologist time and space in the ureteroscope working channel. We compare thulium fiber laser (TFL) high pulse rate/low pulse energy operation to conventional holmium:YAG low pulse rate/high pulse energy operation for fiber-optic suctioning of plaster-ofparis (PoP) stone phantoms. A TFL (wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10 to 350 Hz) and a holmium laser (wavelength of 2120 nm, pulse energy of 35 to 360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz) were tested using 270-μm-core optical fibers. A peak drag speed of ∼2.5 mm∕s was measured for both TFL (35 mJ and 150 to 250 Hz) and holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber-optic suctioning of urinary stone phantoms is feasible. TFL operation at high pulse rates/low pulse energies is preferable to holmium operation at low pulse rates/high pulse energies for rapid and smooth stone pulling. With further development, this novel technique may be useful for manipulating stone fragments in the urinary tract. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Hollow steel tips for reducing distal fiber burn-back during thulium fiber laser lithotripsy

“…13 Using a bare fiber placed in a water bath containing microspheres as visible scatterers, significant water flow was witnessed in the forward direction along the optical path. This flow increased with increasing pulse rate and energy.…”

“…The thulium fiber laser (TFL) (λ ¼ 1908 nm) has recently been studied in the laboratory as an alternative laser lithotripter to holmium (λ ¼ 2120 nm) [7][8][9][10][11][12][13][14] with the main advantage of TFL being the ability to optimally couple into smaller-diameter fibers. The TFL also has a higher absorption coefficient (∼160 cm −1 ) and shorter optical penetration depth in water, compared with holmium (∼28 cm −1 ), which translates into an approximately four times lower ablation threshold.…”

An efficient continuous-wave and Q-switched single-pass two-stage Ho:YLF MOPA system

“…The summarized data of slope efficiencies η slope , optical-tooptical efficiencies η opt-opt , with respect to the incident pump power, as well as the generated laser wavelengths obtained for the Ho:YLF (1) crystal with different transmittances of the output coupler T OC are presented in Table 1.…”

“…Thermal lensing in this calculation was neglected. Due to the imperfect transmittance for the pump wavelength of the dichroic mirror DM2 small portion of the 1940 nm radiation was directed at the Ho:YLF (1) laser output. In order to measure only the pure holmium radiation, wavelengths below 2 μm were additionally separated and transmitted outside the cavity through the dichroic mirrors DM3 and DM4.…”

“…They offer properties, which are required in such applications as material processing, medicine [1], remote sensing [2], or in advanced security and defense systems [3]. The most attractive and popular 2-μm lasers, are the ones based on holmium (Ho 3 þ ) doped materials, oscillating in the region of 2.1 μm [4].…”