Stone/tissue differentiation for holmium laser lithotripsy using autofluorescence.

Area of Science:

• Biomedical Optics
• Urology
• Laser Medicine

Background:

• Holmium laser lithotripsy is effective for urinary stone disintegration.
• Current methods lack real-time feedback for precise fiber positioning.
• Improved safety and handling require continuous monitoring of the treatment fiber's location.

Purpose of the Study:

• To evaluate the potential of 532 nm fluorescence detection for real-time feedback during holmium laser lithotripsy.
• To develop a system for monitoring the treatment fiber's position relative to urinary stones.
• To enhance the safety and efficiency of endoscopic stone removal procedures.

Main Methods:

• A fiber-based fluorescence measurement system was developed.
• Autofluorescence signals from human urinary calculi, artificial stones, and porcine tissues were analyzed.
• Pulsed and continuous-wave (CW) 532 nm excitation were used, along with a lock-in technique for background light insensitivity.

Main Results:

• Human urinary calculi exhibited strong autofluorescence at 532 nm, distinct from porcine tissues.
• Pulsed excitation yielded high fluorescence counts from stones (20,000±11,000) compared to tissue (≤5,500±1,100).
• The lock-in technique enabled sensitive stone detection (1.5-4.3V) with low excitation power (≤1 mW), distinguishing it from background (<0.5V).

Conclusions:

• Autofluorescence detection using 532 nm excitation is a viable method for real-time feedback.
• The lock-in technique effectively isolates stone fluorescence from background noise.
• This fluorescence-based system can enhance the safety and precision of holmium laser lithotripsy by monitoring fiber position.