Spot size variation and skin interaction of long-pulse 1064nm Nd: YAG laser used for varicose veins treatment: A prospective, randomized, assessor-blinded ex vivo study

Background Long-pulsed Nd: YAG 1064 lasers are the standard of care for superficial vein transcutaneous laser treatment. The current concept suggests that the larger the laser spot size, the deeper the penetration into the skin for two reasons: First, wider spot sizes allow the use of higher pulse energy, as energy density (Fluence) decreases exponentially as the beam area widens. Second, the same pulse energy delivered by a smaller beam will be concentrated in the surface owing to the scattering effect. In this study, we examine the effect on skin penetration by changing the spot size of a long-pulsed Nd: YAG 1064 nm laser. Methods 100 different skin samples from 5 human dermolipectomy flaps were shot with 3 consecutive long-pulsed Nd: YAG 1064 nm pulses, one of each with a different spot size (3, 5, and 7 mm), while an energy meter was placed underneath to measure energy. In the first 80 samples, the same total energy (10J) was used for all 240 shots. In the last 20 samples, the same energy density (Fluence) of 100 J/cm2 was used in all 60 shots. Results No variations in mean energy across all spot sizes were observed (3 mm = 3.85 ± 0.89 J, 5 mm = 4.15 ± 0.83 J, 7 mm = 3.96 ± 0.73 J, p = 0.072). Regardless of the spot size, the average pulse energy attenuation was 60.1% with a standard deviation of 8.3%. The average fluence attenuation was 52.3% with a standard deviation of 5.7%. A strong correlation was found in the final energy measured in the same area, regardless of the spot size used. Conclusion In an ex vivo human skin model, varying the spot size of a long-pulsed Nd: YAG 1064 nm laser did not significantly affect energy transmission to the subdermal tissue.