Effects of Cryogen Spray Cooling and High Radiant Exposures on Selective Vascular Injury During Laser Irradiation of Human Skin

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

“…For the purpose of this report, we have defined the dimension of each MTZ (or lesion) as the zone of collagen denaturation as measured histologically by hematoxylin & eosin (H&E) staining [12] or the zone of non-viable cells as measured histologically by nitro blue tetrazolium chloride (NBTC) [13][14]. Previous work has shown the former method to be essentially equivalent to measurement of the loss of birefringence by cross-polarization microscopy of laser-induced thermal coagulation [15].…”

Epidermal and vascular damage analysis of in vivo human skin in response to 595 nm pulsed laser irradiation

“…The first device (We ¼ 5,100) was a standard automobile fuel injector with 1 mm diameter orifice and an attachment nozzle with a length of 2 and 1.5 mm orifice diameter that produced a uniform spray cone with the following spray characteristics (average AE SD): average droplet diameter 26 AE 2 mm and Sauter mean diameter 66 AE 17 mm at a spraying distance of 100 mm. The second device, also used by Tunnell et al [9] (We ¼ 1,100) consisted of a fuel injector with a 1.3 mm orifice diameter (without an attachment nozzle) producing a droplet diameter of 34 AE 4 mm and Sauter mean diameter 116 AE 16 mm at a spraying distance of 90 mm [13].…”

“…CSC has been shown to protect the epidermis from thermal damage in light to moderately pigmented individuals [7][8][9]. However, patients with higher melanin content (Fitzpatrick skin types V and VI) are at a greater risk for nonspecific thermal damage to the epidermis [10][11][12] even when utilizing CSC [9].…”

“…Mathematical models [25][26][27] and an in vivo study [9] have demonstrated that cryogen spurt durations longer than those used clinically increase epidermal protection by further reducing the basal layer temperature before irradiation. Additionally, longer laser pulse durations (10-40 milliseconds) as opposed to pulse durations an order of magnitude shorter, in combination with CSC also provide for greater epidermal protection [9,28] where the increase in laser exposure time allows for thermal diffusion away from the basal layer during laser irradiation, reducing the heat accumulation therein. A high Weber number spray combined with long cryogen spurts and a long laser pulse duration may allow those who currently are at severe risk for non-specific thermal injury to benefit from cutaneous laser therapy.…”

“…Additionally, most of these clinical studies limit the fluences used to 10 J/cm 2 . A few studies report the histological analysis of vasculature in response to irradiation by lasers that are currently used in clinical practice [9,[34][35][36][37]. The second goal of this study was to provide additional morphological and apoptotic histological analysis and correlate the resulting laser-induced purpura to vascular damage.…”