Cynosure (United States)

Early methods of tattoo removal ultimately resulted in unacceptable cosmetic outcomes. While the introduction of laser technology was an improvement over the existing chemical, mechanical, and surgical procedures, the use of nonselective tattoo removal with carbon dioxide and argon lasers led to scarring. Q-switched lasers with nanosecond (10-9) pulse domains were considered to have revolutionized tattoo treatment, by selectively heating the tattoo particles, while reducing the adverse sequelae to adjacent normal skin. Theoretical considerations of restricting pulse duration, to heat tattoo particles to higher temperatures, proposed the use of sub-nanosecond pulses to target particles with thermal relaxation times lower than the nanosecond pulses in Q-switched lasers. Initial studies demonstrated that picosecond (10-12) pulses were more effective than nanosecond pulses in clearing black tattoos. Advances in picosecond technology led to the development of commercially available lasers, incorporating several different wavelengths, to further refine pigment targeting.

Photothermal effects form basis for many uses of optical energy to treat various medical conditions. With an increase in the optical power density, thermally induced phase transitions and chemical transformations take place and the optical properties of the tissue are affected; as a result, local intensity may become non-linear with respect to the instantaneous incident power. These nonlinearities may profoundly affect resulting patterns of the light-tissue interaction; yet they are still poorly understood due to their complexity. In this work, we briefly review the state of the art of clinically relevant nonlinear light-tissue interactions. Then, we report on investigation of the role of opto-thermal nonlinearities in one particular important case: non-ablative fractional treatment of skin. We used the Er:glass laser emitting at the wavelength of 1540 nm, the wavelength mostly absorbed by water. We have shown that propagation of optical energy in the tissue as well as the resulting temperature and damage distributions are significantly influenced by the nonlinear effects. Moreover, the observed nonlinearities led to a self-adaptation phenomenon, manifesting itself in canalization of the optical propagation pathway. Such phenomena may be used to optimize photothermal procedures.

The purpose of this study is to evaluate the efficacy of a long pulse diode laser (Cynosure, Inc.) to target and destroy enlarged sebaceous glands that are preloaded with Indocyanine green (ICG) chromophore. This study was designed in three phases. First, preliminary studies were performed to determine the ability of ICG to penetrate into enlarged sebaceous glands. Once penetration of the sebaceous gland was confirmed, the second phase was to determine the necessary parameters for the diode laser to effectively target the ICG loaded glands. This was done using laser-tissue interaction analysis. The final phase was done with patients that had active acne on their back to determine if selective destruction of the sebaceous glands could be achieved and also to assess the safety and efficacy of this novel treatment for acne. Fluorescence microscopy of biopsy samples show evidence of ICG penetration into the sebaceous glands. Histological examination of biopsy samples from the treated areas finds selective necrosis of the sebaceous glands. Preliminary clinical results demonstrate a decrease in acne noted in the treatment area at 3, 6, and 10 months follow-up. ICG and diode laser treatment is a new approach for the treatment of acne based on experimentally observed selective photothermolysis of the sebaceous glands.

Laser-assisted hair removal is becoming the treatment of choice for removing unwanted hair. The purpose of this work was to determine the long-term efficacy of the long-pulsed infrared (LPIR) laser at shortened treatment intervals for the treatment of bikini hair. Eleven patients received five treatments at 3-week intervals to the right groin using the LPIR laser. Laser parameters were held constant for all treatments: 10 mm spot size, 20 J, and 20-msec pulse duration. Results were evaluated 1 year after the last laser treatment. Hair counts were performed. The average patient had a 78% clearance of hair noted at 1 year with no evidence of scarring or pigmentary changes. A simulated model of cutaneous hair follicles provides evidence that shorter treatment intervals (3 weeks) may be preferable for more complete destruction of the hair follicle bulb and bulge.

Efficient coupling of high power lasers to optical fibers is desired for many applications. An example of these applications is the medical market, where coherent optical power delivered through fibers is used to perform state-of- the-art surgery. We report an efficient method for coupling optical energy from a laser-diode bar to a fiber. This method uses a single surface collimator combined with a two- surface optical transformer. An array of corrector lenses was used to assure that the output of the collimator was appropriately incident on the transformer. Optical efficiency of the collimator, after AR coating, is about 85 percent. The gratin design of the transformer is based on 4- phase level binary optics blazed grating with minimum feature size of 1.5 micrometers . Test results indicate that all the design aspects of our collimator and optical transformer are as expected, and experimental data are well within theoretical expectations. The average tested diffraction efficiency of the optical transformer is as high as 72 percent for one surface. Considering standard 0.8 micrometers process, the efficiency of the transformer for one surface can increase to > 92 percent. To our knowledge, this is the first practical demonstration of the optical transformer concept. These results demonstrate a low-cost and reliable method for efficient coupling of high power laser arrays to fibers for medical and industrial applications.

Pickett, Sally R.N., M.S., C.C.R.N., C.S.; Finlay, Lori R.N., M.S., C.C.R.N. Author Information