Immediate Tissue Responses to Multipulse Low Fluence Laser Treatment in a Chorioallantoic Membrane Model of Port Wine...

The standard Port Wine Stains (PWS) treatment involves using single pulse high fluence (SPHF) laser therapy, which often leads to discomfort and requires multiple sessions. According to the Arrhenius theory, employing multiple pulses with low fluence (MPLF) that have lower peak power could potentially reduce pain while still achieving the therapeutic goals. This study aims to explore the potential of MPLF at 530 nm in achieving the desired clinical endpoints in treating PWS. Additionally, it seeks to validate the predictions of the Arrhenius theory regarding thermal denaturation against empirical data, utilizing established kinetic parameters.

We evaluated vascular responses to SPHF and MPLF approaches using the chorioallantoic membrane (CAM) model and a 530 nm customized fiber laser. Vascular changes were observed with a digital microscope, and temperature was monitored with a thermal camera during irradiation through a 3 × 3 mm spot at 9-10 ms pulse durations, targeting stable coagulum and vessel collapse. First, we established the SPHF threshold, then applied MPLF at 20%-75% of this fluence with a pulse duration of 9-10 ms and a repetition rate of 0.1 or 0.2 Hz (corresponding to 1 pulse every 10 or 5 s, respectively). Additionally, we used the Arrhenius theory with specific kinetic parameters to predict and validate thermal damage.

We observed that both SPHF and MPLF approaches effectively achieved clinical endpoints. Stable coagulum formation was successful at a fluence of 4.2 J/cm² with a pulse width of 10 ms under SPHF. Similarly, MPLF achieved stable coagulum at a lower fluence of 2.2 J/cm², with the thrombus forming after 16 pulses and enlarging by the 32nd pulse. Vessel collapse was also noted at a fluence of 10.8 J/cm² in the SPHF regime and at 5.9 J/cm² with MPLF, with early closure observed after the fourth pulse and completion by the sixteenth. Surface temperature measurements indicated a minor rise following laser exposure, which quickly returned to near baseline levels. Using two sets of activation energies, the Arrhenius model predicted the extent of vessel denaturation and informed the number of pulses required to reach the damage threshold, indicating a lower slope and thus easier damage accumulation with MPLF below the SPHF threshold.

This study provides evidence that using MPLF laser treatment at 530 nm with fluences ranging from 50% to 70% of the SPHF threshold can effectively induce stable coagulum and vessel collapse within the CAM model while maintaining baseline temperatures.