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


METHODS
Rat skin was irradiated in vivo with sequences of 10 Er:YAG laser pulses (repetition rate 20 Hz, pulse duration 150 or 550 micros, single-pulse fluence 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-micros pulses with fluences around 2 J/cm(2) resulted in acute dermal collagen coagulation to a depth of approximately 250 microm, 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 microm.


CONCLUSIONS
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 significant epidermal protection for a given dermal coagulation depth.
Majaron
B
B
Beckman Laser Institute and Medical Clinic, University of California, Irvine, California 92612, USA. boris.majaron@ijs
Kelly
K M
KM
Park
H B
HB
Verkruysse
W
W
Nelson
J S
JS
D000818:Animals; D002056:Burns / Q000209:etiology / Q000473:pathology*; D003131:Combined Modality Therapy; D017679:Cryotherapy / Q000379:methods*; D062109:Dermatologic Surgical Procedures; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000379:methods; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D015601:Injury Severity Score; D053685:Laser Therapy; D007834:Lasers / Q000009:adverse effects*; D009354:Neodymium; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000473:pathology* / Q000528:radiation effects; D012881:Skin Temperature / Q000528:radiation effects
D009354:Neodymium