In vivo multiphoton‐microscopy of picosecond‐laser‐induced optical breakdown in human skin

Abstract

Importance Improvements in skin appearance resulting from treatment with fractionated picosecond-lasers have been noted, but optimizing the treatment efficacy depends on a thorough understanding of the specific skin response. The development of non-invasive laser imaging techniques in conjunction with laser therapy can potentially provide feedback for guidance and optimizing clinical outcome. Objective The purpose of this study was to demonstrate the capability of multiphoton microscopy (MPM), a high-resolution, label-free imaging technique, to characterize in-vivo the skin response to a fractionated non-ablative picosecond-laser treatment. Design, Setting and Participants Two areas on the arm of a volunteer were treated with a fractionated picosecond laser at the Dermatology Clinic, UC Irvine. The skin response to treatment was imaged in-vivo with a clinical MPM-based tomograph at 3h and 24h after treatment and 7 additional time points over a 4-week period. Main Outcomes and Measures MPM revealed micro-injuries present in the epidermis. Pigmented cells were particularly damaged in the process, suggesting that melanin is likely the main absorber for laser induced optical breakdown. Results Damaged individual cells were distinguished as early as 3h post pico-laser treatment with the 532nm wavelength, and 24h post treatment with both 532nm and 1064nm wavelengths. At later time points, clusters of cellular necrotic debris were imaged across the treated epidermis. After 24h of treatment, inflammatory cells were imaged in the proximity of epidermal micro-injuries. The epidermal injuries were exfoliated over a 4-week period. Conclusions and Relevance This observational and descriptive pilot study demonstrates that in-vivo MPM imaging can be used non-invasively to provide label-free contrast for describing changes in human skin following a fractionated non-ablative laser treatment. The results presented in this study represent the groundwork for future longitudinal investigations on an expanded number of subjects to understand the response to treatment in different skin types with different laser parameters, critical factors in optimizing treatment outcome.

Using normal and high pulse coverage with picosecond laser treatment of wrinkles and acne scarring: Long term clinical observations

“…This process results in cavitation bubbles in the skin which, when they expand, may generate shock waves to disrupt the tissue and generate a repair response [13]. In addition to studies with the picosecond device used in this study, similar micro-damage vacuoles have been observed with a prototype fractionated Nd:YAG 1064 nm device with subnanosecond pulses [14] and very recently visualized in-vivo with multiphoton-microscopy (MPM) using a dual wavelength 532 nm and 1064 nm picosecond device with holographic diffractive beam splitter [15]. This study by Balu and colleagues confirmed the study findings of Tanghetti et al with the 755 nm picosecond laser for location of the LIOB's in the epidermis and for melanin being the main target.…”

Moxifloxacin Labeling‐Based Multiphoton Microscopy of Skin Cancers in Asians

“…Excitation laser powers for label‐free MPM and moxifloxacin MPM imaging were approximately 34–37 and 10–17 mW, respectively, in most of the skin specimens. The levels of excitation power were higher than what is usually used for in vivo label‐free MPM imaging (2–5 mW for imaging the superficial epidermis and approximately 10–40 mW for imaging the dermis) . The high excitation powers were not much concern in this study because only ex vivo skin specimens were imaged.…”

Histological characterization of age‐related skin changes following the use of picosecond laser : Low vs high energy

“…According to published evidence, the depth of microinjuries to the skin and the formation of LIOBs has a complex dependence on different laser parameters. 5,10,15 In particular, Ribe et al reported the occurrence of optical breakdowns in the epidermis and dermis depending on the choice of a wavelength and laser energy level. 16 It is believed that one can focus these changes in the epidermis by using a wavelength of 532 nm, or in the upper layers of the papillary dermis by using a wavelength of 1064 nm.…”

“…This relates to the pronounced changes in both the epidermis and dermis when higher energy level was used, a finding observed by other researchers. 5,9,10,15,16 We acknowledge the limitations of our study which include a relative small number of subjects, nonfacial skin biopsies, and a relative short follow-up. Nevertheless, this is the first study to highlight the immediate and delayed histological changes in low vs high energy settings using a further research into the field of the effects of picosecond fractional handpiece in the skin are necessary.…”