COM Stone Dusting and Soft Tissue Ablation With Q-Switched Thulium Fiber Laser

The influence of the parameters of Q-switched thulium fiber laser at 1.94 μm on human calcium oxalate monohydrate (COM) urinary stone and soft tissues has been investigated to determine its efficiency on stone fragmentation and tissue ablation along with surrounding thermal injury. The designed Q-switched thulium fiber laser can be operated with peak powers varying from 93 to 493 W, pulse duration from 350 to 750 ns, and repetition rates from 55 to 135 kHz at 9.5 W average power. Comparative effects on COM stone fragmentation rate and soft tissue ablation by using Q-switched and continuous wave (CW) thulium fiber laser have been studied. The stable pulse from the Q-switched thulium fiber laser at high repetition rate is effective for COM stone fragmentation with very fine particle size, average in the range of 47.85 μm, called dusting, at the fragmentation rate of 12.75 mg/min. Soft tissue ablation employing the Q-switched thulium fiber laser is reasonably clean, leaving minimum residual carbonization of 170 μm and heat-affected zone of 0.76 mm. The Q-switched thulium fiber laser produces two times narrower adjacent tissue damage zone along with four times lower charring region compared to the equivalent CW thulium fiber laser exposure in soft tissue.