Manstein Dieter, Zurakowski David, Thongsima Siremon, Laubach Hans, Chan Henry H
Wellman Center for Photomedicine, Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Lasers Surg Med. 2009 Feb;41(2):149-53. doi: 10.1002/lsm.20711.
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.
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/cm(2). 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.
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.
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.
非剥脱性分次激光皮肤重建是一种皮肤重塑概念，即激光诱导的微小治疗区域（MTZs）被正常存活组织所包围。这种单个损伤直径较小的热损伤模式可实现快速上皮再生，且副作用最小。本体外研究的目的是确定单位表面积的热损伤分数（填充因子）以及与脉冲能量和照射次数相关的损伤大小。
将全层腹部皮肤样本离体暴露于飞梭SR 750激光（Reliant Technologies，加利福尼亚州山景城）下。一组照射在250个MTZ/cm²的单次照射下，脉冲能量范围为8至40 mJ。另一组照射在10 mJ下进行，照射次数从1至30次。通过用氯化硝基四氮唑蓝（NBTC）染色孵育表皮片来评估热损伤模式。通过对数字显微照片进行图像分析（ImageJ，美国国立卫生研究院，马里兰州贝塞斯达）来确定单个MTZ的大小和填充因子。
热损伤区的宽度与所用脉冲能量直接相关。填充因子与照射次数没有统一的关系。由于单个MTZ的随机分布，即使照射次数更多，仍发现一些残留的未受损组织。由于形成了热损伤簇，即重叠的单个MTZ，我们定义为微观治疗簇（MTC）的所得簇状损伤的大小随照射次数呈线性增加。
我们描述了与照射次数相关的填充因子，并证明单个损伤的平均大小取决于照射次数。MTZ的聚集导致了MTC的形成，其平均大小随照射次数增加。这些发现的临床意义取决于进一步的研究。
