Could titanium oxide coating from a sol-gel process make stone baskets more resistant to laser radiation at 2.1 μm?

Abstract

Background: Stone baskets could be easily destroyed by Holmium:YAG-laser at an endourologic treatment, with respect to this, we try to improve the resistance by coating them with a titanium oxide layer. The layer was established by a sol-gel-process.

Materials and methods: Six new baskets (Equadus, Opi Med, Ettlingen, Germany) were used: 1.8 Ch. with 4 wires (diameter 0.127 mm). Three baskets were coated with a layer of titanium oxide established by a sol-gel process at the BioCerEntwicklungs GmbH in Bayreuth (~100 nanometres thickness). The lithotripter was a Holmium:YAG laser (Auriga XL, Starmedtec, Starnberg, Germany). 10 uncoated and 10 coated wires were tested with 610 mJ (the minimal clinical setting) and 2 uncoated and 2 coated wires were tested with 110 mJ. The wires were locked in a special holding instrument under water and the laser incident angle was 90°. The endpoint was gross visible damage to the wire and loss of electric conduction.

Results: Only two coated wires resisted two pulses (one in the 610 mJ and one in the 110 mJ setting). All other wires were destroyed after one pulse.

Conclusion: This was the first attempt at making stone baskets more resistant to a Holmium:YAG laser beam. Titanium oxide deposited by a sol-gel-process on a titanium-nickel alloy did not result in better resistance to laser injuries.

Figure 1

Stone basket with 4 wires 1,8 F(Equadus Opti Med, Ettlingen, Germany).

Figure 2

Schematic of the experimental setup.

Figure 3

The investigational setting with the “multimeter”, the holding instrument and the laser fibre with a 90° incident angle.

Figure 4

Microscopic picture of the gross visible damage of the wire with the typical melting drop (upper picture with a magnification of 60 and lower picture with a magnification of 200).