The effects of multiple passes on the epidermal thermal damage pattern in nonablative fractional resurfacing

Abstract

Background and Objective Nonablative fractional resurfacing is a concept of cutaneous re‐modeling whereby laser‐induced microscopic treatment zones (MTZs) are surrounded by normal viable tissue. Such thermal damage pattern with a small diameter of individual lesions allows fast re‐epithelialization with minimal side effects. The purpose of this in vitro study was to determine the fraction of thermal injury per unit surface area (fill factor) and lesion size in relation to pulse energy and number of passes. Methods Full thickness abdominal skin samples were exposed ex vivo to the Fraxel SR 750 laser (Reliant Technologies, Mountain View, CA). One set of exposures was performed for pulse energies in the range of 8 to 40 mJ for a single pass at 250 MTZ/cm2. A second set of exposures was performed at 10 mJ with number of passes from 1 to 30. The thermal damage pattern was assessed by incubation of epidermal sheets with NitroBlueTetrazoliumChloride (NBTC) stain. Size of individual MTZ and fill factor were determined by image analysis (ImageJ, NIH, Bethesda, MD) of digital micrographs. Results Width of the thermal injury zone was directly related to the pulse energy used. The fill factor did not have a uniform relationship with the number of passes. Due to the stochastic placement of individual MTZs, even for greater number of passes, some residual undamaged tissue was found. Due to formation of thermal damage clusters, defined as overlapping individual MTZs, the size of the resulting clustering lesions which we defined as microscopic treatment cluster (MTC) increased linearly as a function of the number of passes. Conclusion We have described the fill factor as it relates to the number of passes and have demonstrated that the average size of individual lesions depends on the number of passes. Clustering of MTZs lead to the development of MTC, the average size of which increased with the number of passes. The clinical implications of these findings are contingent on further studies. Lasers Surg. Med. 41:149–153, 2009. © 2009 Wiley‐Liss, Inc.

Treatment of facial photodamage and rhytides using a novel 1,565 nm non‐ablative fractional erbium‐doped fiber laser

“…The device delivers laser energy non‐sequentially using a sophisticated patent pending scanning algorithm. Variations in microbeam distribution and clustering of microthermal treatment zones due to multiple passes of laser energy delivery, as seen with rolling‐pattern handpieces, are thereby prevented . An integrated, thermokinetically cooled sapphire crystal treatment tip enhances epidermal protection and reduces intraoperative discomfort.…”

Which Type of Atrophic Acne Scar (Ice-pick, Boxcar, or Rolling) Responds to Nonablative Fractional Laser Therapy?

“…A standardized scoring system 4 and an objective assessment is also necessary to evaluate the results. 3,5 Fractional lasers have been studied histologically [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and clinically using ablative (carbon dioxide (CO 2 ) 25,[34][35][36][37][38][39][40][41][42]49,58,59 and erbium-doped yttrium aluminum garnet (Er:YAG) 24,25,59 ) and nonablative 26,27,[31][32][33][43][44][45][46][47][48][49] technology. Although some excellent ...…”

Fraktionierte nicht ablative Laser

“…Alle Systeme erfordern jedoch multiple Interventionen, typischerweise werden 4-6 Behandlungen alle 4 Wochen erforderlich, um eine moderate Verbesserung von Falten [1,36] und anderen Phänomenen der chronisch lichtgealterten Haut zu erreichen [69]. Bei ausgeprägten Veränderungen sind die Systeme jedoch nicht e zient genug [5].…”

“…Frequenz zu minimieren [1]. Infolge des Erhalts unbehandelten Gewebes in der Umgebung einer jeden MTZ wird sichergestellt, dass sowohl im epidermalen als auch im Bereich des dermalen Gewebes das Remodelling sicher infolge des Erhalts zellulärer Funktionen der Keratinozyten, Stammzellen, Melanozyten sowie der Entzündungszellen induziert wird.…”