Er:YAG laser skin resurfacing using repetitive long‐pulse exposure and cryogen spray cooling: I. Histological study*

Abstract

Background and Objective: To evaluate histologically the characteristics of repetitive Er:YAG laser exposure of skin in combination with cryogen spray cooling (CSC), and its potential as a method of laser skin resurfacing. Study Design/Materials and Methods: Rat skin was irradiated in vivo with sequences of 10 Er:YAG laser pulses (repetition rate 20 Hz, pulse duration 150 or 550 ms, single-pulse¯uence 1.3±5.2 J/cm 2 ). In some examples, CSC was applied to reduce epidermal injury. Histologic evaluation was performed 1 hour, 1 day, 5 days, and 4 weeks post-irradiation. Results: A sequence of ten 550-ms pulses with¯uences around 2 J/cm 2 resulted in acute dermal collagen coagulation to a depth of approximately 250 mm, without complete epidermal ablation. CSC improved epidermal preservation, but also diminished the coagulation depth. Four weeks after irradiation, neo-collagen formation was observed to depths in excess of 100 mm. Conclusion: Dermal collagen coagulation and neo-collagen formation to depths similar to those observed after CO 2 laser resurfacing can be achieved without complete ablation of the epidermis by rapidly stacking long Er:YAG laser pulses. Application of CSC does not offer signi®cant epidermal protection for a given dermal coagulation depth.

Nonablative Laser and Light Rejuvenation

“…Subsequent neocollagen formation was noted histologically by a band of parallel collagen fibrils in the superficial dermis with a thickness of 100 to 250 µm (Figure 3). 24 These dermal changes were significant and closely approximated results seen after CO 2 LSR; however, although the epidermis was not completely ablated, moderate epidermal damage occurred. The addition of CSC before, or during and after, the sequence of laser pulses improved epidermal preservation but also significantly diminished the depth of collagen coagulation.…”

Treatment of lichen pilaris with a Q-switched Nd:YAG laser in quasi long-pulsed mode: A case report (a secondary publication)

“…Even though medical treatments for the disease are commonly performed including topical preparations such as urea ointment, salicylic acid petrolatum, vitamin A ointment, Vitamin A/D ointment, and Vitamin A ingested orally, these approaches, which are hard to be evaluated as successful from our experience, often result in forcing patients to wait until the spontaneous regression of the condition. In recent years, procedures using various types of low fluence lasers have been widely used with devfices based on pulsed light sources, or radiofrequency (RF) energy, as a skin rejuvenation approach to refresh the skin and improve follicular dilatation, and the results have been reported [4][5][6][7] . Initially, the effect of low level laser therapy (LLLT) on skin had been reported as an action to enhance the treatment of recalcitrant ulcers and accidental or iatrogenic trauma 8) using the effect of biostimulation or photobioactivation 9) but it became to be referred to as photo-rejuvenation therapy 10, 11) later due to the skin rejuvenation effect.…”

Novel model for evaluation of epidermal preservation and dermal collagen remodeling following photorejuvenation of human skin

“…Laser irradiation procedures resembled those used in previous animal studies in our laboratory [9,10]. The 4 mm laser hand-piece was mounted 25 cm above the target surface to increase the spot size, resulting in a single-pulse energy density of 1.4 AE 0.2 J/cm 2 in the central region of the irradiated spot.…”

“…The laser irradiation parameters were selected to resemble those used successfully for laser-induced collagen stimulation and dermal remodeling in previous animal studies. In that work, repetitive low-fluence Er:YAG laser irradiation was proven to induce deep collagen coagulation and subsequent neo-collagen formation with epidermal preservation [9,10].…”