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The effects of pulse energy variations on the dimensions of microscopic thermal treatment zones in nonablative fractional resurfacing
Author(s) -
Bedi Vikramaditya P.,
Chan Kin Foong,
Sink R. Kehl,
Hantash Basil M.,
Herron G. Scott,
Rahman Zakia,
Struck Steven K.,
Zachary Christopher B.
Publication year - 2007
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.20406
Subject(s) - ex vivo , in vivo , stain , laser , staining , coagulative necrosis , biomedical engineering , materials science , pulse (music) , chemistry , biophysics , pathology , optics , medicine , biology , physics , microbiology and biotechnology , detector
Background and Objectives We examined the effects of pulse energy variations on the dimensions of microscopic thermal injury zones (MTZs) created on human skin ex vivo and in vivo using nonablative fractional resurfacing. Materials and Methods A Fraxel® SR laser system emitting at 1,550 nm provided an array of microscopic spots at variable densities. Pulse energies ranging from 4.5 to 40mJ were tested on human abdominal skin ex vivo and in vivo. Tissue sections were stained with hematoxylin and eosin (H&E) or nitro blue tetrazolium chloride (NBTC) and MTZ dimensions were determined. Ex vivo and in vivo results were compared. Dosimetry analyses were made for the surface treatment coverage calculation as a function of pulse energy and collagen coagulation based on H&E stain or cell necrotic zone based on NBTC stain. Results Each MTZ was identified by histological detection of a distinct region of loss of tissue birefringence and hyalinization, representing collagen denaturation and cell necrosis within the irradiated field immediately, 1, 3, and 7days after treatment. At high pulse energies, the MTZ depth could exceed 1 mm and width approached 200 µm as assessed by H&E. NBTC staining revealed viable interlesional tissue. In general, no statistically significant difference was found between in vivo and ex vivo depth and width measurements. Conclusions The Fraxel® SR laser system delivers pulses across a wide range of density and energy levels. We determined that increases in pulse energy led to increases in MTZ depth and width without compromising the structure or viability of interlesional tissue. Lasers Surg. Med. 39:157–163, 2007. © 2007 Wiley‐Liss, Inc.