Interspersion of fragmented fiber's splinters into tissue during pulsed alexandrite laser lithotripsy

Laser induced shockwave lithotripsy (LISL) on artificially inserted human renal calculi was realized in explanted pig ureters. A pulse stretched Alexandrite solid state laser was used at 750nm. Pulses of 350ns and 1μs duration were transmitted through a 250μm all silica fiber onto a stone surface, keeping the fiber tip in contact with a stone close to the ureter wall. The high power density of the 350ns pulses lead to an optical breakdown inside the distal fiber tip causing fiber fragmentation of about 28mm/100 pulses. Deep penetration of the fiber fragments into the ureter wall was proven histologically. Fiber fragmentation was avoided by increasing the pulse duration up to 1μs. Risks for patient treatment caused by short pulse lithotripsy are discussed.