Comparative Tissue Effects of Pulsed Diode-Pumped Tm:YAG vs CW Tm:YAG and Pulsed Ho:YAG Lasers

Overview

This study compares tissue responses of a novel diode-pumped pulsed Thulium:YAG laser with continuous wave Thulium:YAG and pulsed Holmium:YAG lasers in porcine kidney tissue. Results demonstrate distinct incision depths and laser damage zones dependent on laser type and power, with the pulsed Tm:YAG showing intermediate cutting and damage characteristics.

Background

Holmium:YAG (Ho:YAG) and Thulium:YAG (Tm:YAG) lasers are widely used in urologic surgery due to their emission in the 2 µm wavelength range. Despite similar wavelengths, pulsed Ho:YAG and continuous wave (CW) Tm:YAG lasers produce different tissue effects: Ho:YAG causes mechanical tissue disruption via steam bubble dynamics, while CW Tm:YAG induces continuous vaporization with superior hemostasis. A novel diode-pumped Tm:YAG laser capable of pulsed emission aims to combine these effects, warranting comparative evaluation of tissue interactions.

Data Highlights

Key Findings

• At low power (5 W), pulsed Tm:YAG produced shallow incisions (275 µm) while CW Tm:YAG caused no visible cut, and pulsed Ho:YAG produced the deepest incision (975 µm).
• At intermediate power (40 W), pulsed Tm:YAG incisions (975 µm) were deeper than CW Tm:YAG (336 µm) but shallower than pulsed Ho:YAG (1400 µm).
• At high power (80 W), CW Tm:YAG created the deepest incisions (3216 µm), followed by pulsed Ho:YAG (2258 µm) and pulsed Tm:YAG (2125 µm).
• Laser damage zones (outer coagulation plus necrotic zones) were generally similar across lasers at higher powers, ranging approximately 600–1000 µm in depth.
• Macroscopically, Ho:YAG produced coarse cuts without carbonization, CW Tm:YAG created smooth cuts with dark carbonization, and pulsed Tm:YAG yielded smooth cuts with light caramel coloration and minimal charring.
• The pulsed Tm:YAG laser combines features of both CW Tm:YAG and pulsed Ho:YAG, offering intermediate incision depths and favorable tissue effects.

Clinical Implications

The pulsed diode-pumped Tm:YAG laser offers a balance between cutting efficiency and tissue preservation, potentially enhancing surgical precision and hemostasis. Its intermediate incision depth and reduced charring compared to Ho:YAG may improve clinical outcomes in urologic procedures. Understanding these differential tissue effects can guide laser selection tailored to specific surgical needs.

Conclusion

The novel pulsed diode-pumped Tm:YAG laser demonstrates distinct and clinically relevant tissue interactions compared to CW Tm:YAG and pulsed Ho:YAG lasers, combining advantageous features of both. These findings support its potential utility in urologic surgery requiring precise cutting with controlled tissue damage.

References

1. LISA Laser Products GmbH -- Technical and Experimental Laser Data
2. Previous Studies on Tm:YAG and Ho:YAG Laser Tissue Effects (Refs 5-8)