The effects of pulse energy variations on the dimensions of microscopic thermal treatment zones in nonablative fractional resurfacing

Abstract

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 1 SR laser system emitting at 1,550 nm provided an array of microscopic spots at variable densities. Pulse energies ranging from 4.5 to 40 mJ 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 7 days after treatment. At high pulse energies, the MTZ depth could exceed 1 mm and width approached 200 mm 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 1 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.

Ex vivo histological characterization of a novel ablative fractional resurfacing device

“…In a previous study, we recognized the limitation of vertical sectioning accurately locating the widest and deepest boundaries of a lesion [18]. To overcome this limitation, we decided to utilize a horizontal serial frozen sectioning technique that allowed visualization of the true center of each cavity thus providing a more precise estimate of lesion width.…”

“…The laser handpiece was translated at a specific velocity by using a precision linear stage driven by an ESP 300 motion controller (Newport Co., Irvine, CA). The firing rate of the laser was automatically adjusted by the laser handpiece to produce a specific density of lesions [18]. In the pulse energy range of 8-20 mJ, we encountered a 17 AE 4% discrepancy between set (value on user interface) and measured pulse energy.…”

“…The lesion dimensions were measured with a proprietary Visual Basic computer program (Reliant Technologies, Inc.) [18]. The lesion dimension represents the maximum depth and width of the ablated cavity plus the outermost border of the coagulation or viability zone histologically determined by H&E or LDH staining, respectively.…”

Ablative Fractional 10 600 nm Carbon Dioxide Laser Versus Non-ablative Fractional 1540 nm Erbium-Glass Laser in Egyptian Post-acne Scar patients

“…Minimal side effects, downtime and superior results were all demonstrated in multiple previous studies. 12,13 This study was designed to assess and compare the effectiveness of fractional CO 2 laser and fractional non-ablative 1540 nm erbium doped glass laser in the treatment of atrophic acne scars in Egyptian patients. We aimed to investigate the safety of the treatments as well as patients satisfaction following treatment as well.…”

The Advent of Laser Therapies in Dermatology and Urology: Underlying Mechanisms, Recent Trends and Future Directions

“…As a result, fractional photothermolysis [50] and fractional resurfacing [51] became the best solutions for resurfacing and dermal remodeling while offering a comfortable treatment modality with a low side-effects profile. Fractional photothermolysis and resurfacing produce microscopic thermal zones (In the ablative mode, termed microscopic treatment zones) or MTZs that -can be delivered very rapidly depending on the enabling technologies.…”