Human hair is a keratinous tissue composed mostly of flexible keratin, which can form a complex architecture consisting of distinct compartments or units (e.g. hair bulb, inner root sheath, shaft). Variations in hair shaft morphology can reflect ethnical diversity, but may also indicate internal diseases, nutritional deficiency, or hair and scalp disorders. Hair shaft abnormalities in cross section and diameter, as well as ultramorphological characterization and follicle shapes, might be visualized non-invasively by high-speed 2D and 3D optical coherence tomography (OCT). In this study, swept source OCT (ThorLabs) was used to examine human hair. Preliminary results showed that the high-speed OCT was a suitable and promising tool for non-invasive analysis of hair conditions.
Near infrared Nd:YAG pulsed laser treatment had been proved to be an efficient method to treat large-sized vascular
malformations like leg telangiectasia for deep penetrating depth into skin and uniform light distribution in vessel.
However, optimal clinical outcome was achieved by various laser irradiation parameters and the key factor governing
the treatment efficacy was still unclear. A mathematical model in combination with Monte Carlo algorithm and finite
difference method was developed to estimate the light distribution, temperature profile and thermal damage in epidermis,
dermis and vessel during and after 1064 nm pulsed Nd:YAG laser irradiation. Simulation results showed that epidermal
protection could be achieved during 1064 nm Nd:YAG pulsed laser irradiation in conjunction with cryogen spray
cooling. However, optimal vessel closure and blood coagulation depend on a compromise between laser spot size and
With low risk of complications and no down-time, the non-ablative photorejuvenation is playing an increasing role
in the therapy of the photodamaged skin. The light dose is one of the key factors that affect the performance of the
photorejuvenation. Monitoring the tissue response during the procedure of laser irradiation would help to determine
whether the light dose is appropriate. In this study, we developed a new approach to monitor the instant response of
tissue irradiated by laser device by measuring the change of the total attenuation coefficient of the tissue with optical
coherence tomography. The total attenuation coefficient was deduced from the raw data obtained by OCT with single
scattering mode. Spatial and temporal equalizations were employed to improve the signal-to-noise ratio. We measured in
vivo the total attenuation coefficients of the mouse back skin before and after laser irradiation. The total attenuation
coefficients of the tissue reduced approximately 60% immediately after laser irradiation and then kept constant in a short
time. The reduction of the attenuation coefficient depended on the light dose. These results demonstrated that the new
approach could be a potential tool for monitoring in clinic in the future.
Nonablative skin remodeling is a new light treatment approach for photodamaged skin. Compared to ablative CO2 or
Er:YAG laser resurfacing, dermabrasion, and chemical peels, the clinical objective of nonablative skin remodeling is to
maximize thermal damage to upper dermis while minimizing injury to the epidermis and surrounding tissue,
consequently decreasing potential complications and shortening long recuperation periods.
Histological analysis of preoperative and postoperative biopsies using H&E or special stains has indicated the dermal
thermal injury, which resulting in collagen denaturation, is the most important mechanism of nonablative skin
remodeling for improving skin situation. And the extent of improvement of skin situation corresponded to the formation
of a new band of dense, compact collagen bundles in the papillary dermis. The diversity of individual skin condition
influences the choice of pulsed light treatment parameters, and further influences the degree of dermal thermal damage,
thus the efficacy of nonablative skin remodeling remains unstable.
Recently, multiphoton microscopy has show a promising application for monitoring skin thermal damage, because
collagen could produce strong second harmonic generation (SHG). And SHG intensity is presumably proportional to the
percentage of collagen in dermis. In this paper, the auto-fluorescence (AF) intensity and SHG intensity of mice skin
irradiated by pulsed Nd:YAG laser were measured and imaged with multiphoton microscope, and the results show the
ratio of SHG to AF decreases with the increase of irradiation exposure dose, and could be a quantitative technique to
assess dermal thermal damage, and could further benefit the choice of light treatment parameters.
Intense pulsed light system in combination with contact cooling is a useful tool for treating photodamaged skin. It can
emit broadband light, and target different kind of pigment in skin. But the pressure on skin often influences the
temperature field distribution inside the skin when the treatment head contacts skin. In this paper, we assumed the
pressure on skin would cause the changes of thermal diffusivity and optical absorption coefficient. Under these
assumptions, the temperatures inside skin induced by intense pulsed light system with contact cooling were modeled
using Monte Carlo method and explicit finite difference bioheat conduction equation. The results suggest that pressure
imposed on skin surface should be taken into account when using pulsed light system with contact cooling to treat
lesions inside the skin.
Several methods have been used to improve the esthetic appearance of photodamaged skin including dermabrasion, chemical peels and laser resurfacing using CO2 and Er:YAG laser. These procedures sacrifice epidermis, resulting in a long recuperation period and potential complications including persistent scarring, infection, hyperpigmentation, etc. Compared to ablative CO2 or Er:YAG laser resurfacing, non-ablative photorejuvenation technologies are playing an increasing role in the treatment of photodamaged skin. The clinical objective of which is to maximize thermal damage to upper dermis while minimizing injury to overlying skin. A variety of laser and non-laser systems have been used in the initial stage for this treatment. In our review, different treatment modalities have resulted in varying degrees of clinical effects. The basic mechanisms relate to improvement in employing non-ablative technologies are also discussed. Photorejuvenation is still not a fully established clinical tool for cosmetic treatment according to our review, therefore more research on basic mechanisms should be made.
“Nonablative skin photorejuvenation” is a new treatment for photoaged skin, which is to wound the upper dermis in order to induce dermal fibrosis and improve the clinical appearance. In this paper, the penetration depths of the light emitted by intense pulsed light source (IPLS) were analyzed, and the results show the IPLS was suitable for nonablative skin photorejuvenation. A new method with thermal texture maps (TTM) technology for exploring the mechanisms and repairing processes in the nonablative treatment of photoaged skin was presented.