Effect of dual-optical pulses with temporal energy distribution on laser ablation performance in in vivo zebrafish model

A Q-switched laser system has been used in a single-pulse mode for skin melasma treatments because of instant heat deposition in the target. Despite the efficient ablation of the melanophores in the skin, the single, high-fluence pulse often causes undesirable damage to the surrounding tissue, leading to high recurrence rates. This study aims to investigate the feasibility of dual-optical pulses with a temporal energy distribution on the melasma treatment in in vivo zebrafish models in comparison to that of the single optical pulse. Based on the optical detection, the dual-optical pulses had a temporal energy distribution ratio of 4:1 and an interval of 61 μs between the two consecutive pulses. According to the histological analysis, the dual pulses removed melanophores and induced a few apoptotic nuclei with minimal recurrence. This study demonstrated that the feasibility of dual-optical pulses (energy ratio = 4:1) could enhance the laser ablation performance in vivo.

Erbium:YAG laser augments the penetration of cryotherapy

Cryotherapy is commonly used during dermatologic practice. Several modifications such as an "add-on" to topicals or intralesional applications have been already defined to enhance efficacy. The aim of this study is to test our hypothesis that ablative laser application before cryotherapy would increase the depth of freezing.Throughout this experiment, target points received either cryotherapy alone or a combination of erbium:yttrium-aluminum garnet (erbium:YAG) laser and cryotherapy. Freezing durations of 10 (C10), 20 (C20), and 30 seconds (C30) were investigated. Erbium:YAG laser groups received equal high energy shots with different pulse durations (100 μs versus 1500 μs) before freezing. The treatment points were arranged on the peripheral side of porcine skin specimens, and dermoscopic images revealing the iceball visible from the lateral side were immediately captured. Repeated experimental results were compared by Wilcoxon's test. The comparison of the vertical length of the iceball between the three different freezing durations of 10 seconds, 20 seconds, and 30 seconds was statistically significant (p<0.05). The vertical length of the iceball was higher in both laser groups receiving 30-second freezing (mean ± SD: 4.32±0.53, 3.9±0.38 for micro-short pulse (MSP) and extra-long pulse (XLP), respectively) when compared with 30-second freezing alone (mean ± SD:3.51±0.44) (p=0.016). The two laser settings did not reveal a difference for the penetration of 30-second freezing (p=0.122). In this study, through visual monitorization of the iceball, erbium:YAG laser is found to augment the penetration of cryotherapy. The defined combination regimen has the potential to ameliorate treatment outcomes of cryotherapy.