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20 mJ, 1 ps Yb:YAG Thin-disk Regenerative Amplifier
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Effect of Pulse Modulation on Diode-Pumped Laser Lithotripsy.
Nitesh Katta1, Katherine Sikorski1, Joel M H Teichman2
1Beckman Laser Institute and Medical Clinic, University of California at Irvine, Irvine, California, USA.
Journal of Endourology
|May 27, 2025
Summary
Optimizing pulse modulation for thulium lasers (Tm:YAG and TFL) significantly enhances kidney stone lithotripsy by increasing energy transfer and stone removal. Synchronizing the second pulse with vapor bubble dynamics maximizes effectiveness.
Area of Science:
- Medical physics and biomedical engineering
- Laser-tissue interaction
- Urological device development
Background:
- Kidney stone lithotripsy commonly uses lasers, but energy transfer efficiency through saline can be a limiting factor.
- Thulium lasers, including Tm:YAG and Thulium Fiber Lasers (TFL), are utilized for their specific wavelengths in stone fragmentation.
- Pulse modulation strategies are being explored to improve laser ablation efficiency and stone removal.
Purpose of the Study:
- To investigate the impact of pulse duration, energy, and interpulse delay on energy transfer for kidney stone lithotripsy.
- To determine if an optimal pulse modulation profile maximizes radiant energy transfer (RETE).
- To assess if enhanced energy transfer via pulse modulation leads to greater stone volumetric removal.
Main Methods:
- Radiant energy transmission efficiency (RETE) and ablation volumes were measured using phantom and human kidney stones.
- Experiments involved diode-pumped thulium yttrium aluminum garnet (Tm:YAG) and thulium fiber lasers (TFL) at various standoff distances.
- Fast camera imaging and optical coherence tomography were used to analyze vapor bubble dynamics and crater volumes.
Main Results:
- Dual-pulse modulation with Tm:YAG lasers increased RETE by up to 75% at a 1 mm standoff distance compared to single-pulse.
- Optimal dual-pulse modulation resulted in significantly greater stone volumetric removal for most stone types with Tm:YAG.
- Thulium Fiber Lasers (TFL) showed similar trends, though with some variability across different stone compositions.
Conclusions:
- Pulse-modulated Tm:YAG and TFL lasers can enhance photon delivery through saline when the initial pulse is optimized.
- An optimal pulse modulation profile, synchronized with vapor bubble collapse, achieves the highest RETE.
- Improved RETE through optimized pulse modulation directly correlates with increased stone volumetric removal in lithotripsy.
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