ABSTRACT
Laser-tissue vaporization through a fiber catheter is evolving into a major category of surgical operations to remove diseased tissue. Currently, during a surgery, the surgeon still relies on personal experience to optimize surgical techniques. Monitoring tissue temperature during laser-tissue vaporization would provide important feedback to the surgeon; however, simple and low-cost temperature sensing technology, which can be seamlessly integrated with a fiber catheter, is not available. We propose to monitor tissue temperature during laser-tissue vaporization by detecting blackbody radiation (BBR) between 1.6â µm-1.8â µm, a relatively transparent window for both water and silica fiber. We could detect BBR after passing through a 2-meter silica fiber down to â¼70°C using lock-in detection. We further proved the feasibility of the technology through ex vivo tissue studies. We found that the BBR can be correlated to different tissue vaporization levels. The results suggest that this simple and low-cost technology could be used to provide objective feedback for surgeons to maximize laser-tissue vaporization efficiency and ensure the best clinical outcomes.
ABSTRACT
Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391 mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.
