Aiming to personalized laser therapy for nevus of Ota: melanin distribution dependent parameter optimization.

Aiming to the personalized laser therapy of nevus of Ota (NO), a local thermal non-equilibrium model was employed to optimize laser wavelength, pulse duration, and energy density under different melanin depth and volume fraction. According to our simulation, the optimal pulse duration is between 15 and 150 ns to limit heat transfer inside the hyperplastic melanin, and 50 ns is recommended to decrease the energy absorption by normal melanin in epidermis. Correlations of the minimum and the maximum energy densities are proposed with respect to melanin depth and volume fraction for the 755-nm and 1064-nm lasers. For the same NO type, the therapy window of the 755-nm laser is larger than that of 1064-nm. For NO with shallow depth or low volume fraction, the 755-nm laser is recommended to make the treatment more stable owing to its lager therapy window. For deeper depth or higher volume fraction, the 1064-nm laser is recommended to avoid thermal damage of epidermis. Through comparison with clinical data, the optimized laser parameters are proved practicable since high cure rate can be achieved when energy density falls into the range of predicted therapy window. With developing of non-invasive measurement technology of melanin content and distribution, personalized treatment of NO maybe possible in the near future.

Histopathological evaluation of the R134a multipulsed spray cooling assisted 1210 nm laser lipolysis by the murine model in vivo.

BACKGROUND AND OBJECTIVE: Owing to the greater absorption affinity for lipo-rich tissue than water, the 1210 nm laser is a promising candidate for transcutaneous lipolysis in the near-infrared band. However, fat reduction is limited because laser therapy may yield thermal injury of normal tissue. A new protocol to incorporate multipulsed cryogen spray cooling is beneficial to improve the lipolysis effect, and the parameters of laser and cooling can be optimized via skin histopathological analysis. MATERIALS AND METHODS: A murine in vivo model of inguinal tissue of SD rats was established to test the effectivity of transcutaneous lipolysis protocol by R134a multipulsed spray cooling assisted 1210 nm laser irradiation. Tissue response of lipolysis with/without cooling 10 days post the treatment was evaluated by histopathological analysis of skin samples stained with hematoxylin-eosin (HE), through which safe and effective parameters for lipolysis were determined. RESULTS: From histopathological analysis of the inguinal tissue of SD rats irradiated by the 1210 nm laser alone, the optimal durations are respectively 7 and 3 s (seconds) for low-dosage (6 W) and high-dosage (9 W) therapy, with pronounced lipolysis effect and minimum injury of skin tissue. The multipulsed spray cooling by R134a with a pulse duration of 10 ms (milliseconds), a pulse delay of 2000 ms, and a pulse number of 5 can be introduced to assist the 1210 nm laser therapy with a power of 9 W and a duration of 7 s to achieve desirable fat liquefaction while keeping the complete structure of skin tissue as well as esthetic-related beneficial effects of hair removal and skin rejuvenation. CONCLUSION: Excellent lipolysis effect can be achieved via R134a multipulsed spray cooling assisted high-dosage 1210 nm laser irradiation with reasonably matched laser and cooling parameters. The protocol is as follows: Start MP-CSC for one cycle, and then fire the laser with specific power and duration, while keeping MP-CSC accordingly. This new protocol may promote the safe and effective clinical implement of transcutaneous laser lipolysis in body contouring.