Characterization of an optimized light source and comparison to pulsed dye laser for superficial and deep vessel clearance.

BACKGROUND AND OBJECTIVE: An arc lamp-based device providing optimized spectrum and pulse shape was characterized and compared with two pulsed dye laser (PDL) systems using a vascular phantom. Safety and effectiveness for facial telangiectasia are presented in clinical case studies. STUDY DESIGN/MATERIALS AND METHODS: An optimized pulsed light source's (OPL) spectral and power output were characterized and compared with two 595 nm PDL devices. Purpuric threshold fluences were determined for the OPL and PDLs on Fitzpatrick type II normal skin. A vascular phantom comprising blood-filled quartz capillaries beneath porcine skin was treated by the devices at their respective purpuric threshold fluences for 3 ms pulse widths, while vessel temperatures were monitored with an infrared (IR) camera. Patients with Fitzpatrick skin types II-III received a split-face treatment with the OPL and a 595 nm PDL. RESULTS: The OPL provided a dual-band output spectrum from 500 to 670 nm and 850-1,200 nm, pulse widths from 3 to 100 ms, and fluences to 80 J/cm(2). The smooth output power measured during all pulse widths provides unambiguous vessel size selectivity. Percent energy in the near infra-red increased with decreasing output power from 45% to 60% and contributed 15-26% to heating of deep vessels, respectively. At purpuric threshold fluences the ratio of OPL to PDL vessel temperature rise was 1.7-2.8. OPL treatments of facial telangiectasia were well-tolerated by patients demonstrating significant improvements comparable to PDL with no downtime. CONCLUSIONS: Intense pulsed light (IPL) and PDL output pulse and spectral profiles are important for selective treatment of vessels in vascular lesions. The OPL's margin between purpuric threshold fluence and treatment fluence for deeper, larger vessels was greater than the corresponding margin with PDLs. The results warrant further comparison studies with IPLs and other PDLs.

The role of laser tunnels in laser-assisted lipolysis.

BACKGROUND AND OBJECTIVES: Laser-assisted lipolysis (LAL) devices are used as adjuncts to liposuction that create laser tunnels to heat the adipose and connective tissue. Available systems vary significantly across choice of wavelengths, power delivery, and tip design. Rationale are developed for optimum laser parameters evaluated with physical principles and in controlled ex vivo tests. STUDY DESIGN/MATERIALS AND METHODS: A computer model for radiation propagation, thermal conduction and coagulation was developed to study laser tunnels formed in human adipose tissue. An ex vivo study with porcine tissue compared laser tunnels created by a device that operates in short-pulse mode with a 0.6 mm diameter fiber emitting lipid non-selective laser wavelengths to a device that operates in continuous-wave (CW) mode with a 1.5 mm diameter fiber emitting lipid- and water-selective laser wavelengths. RESULTS: Photothermolytic heating is the optimum mechanism to control delivery of heat to the tissue. Fiber tip surface power density can be optimized for ease of penetration and good volumetric heating while avoiding extremely high peak temperatures. CW rather than pulsed laser emission also minimizes peak temperature rise that can interfere with tunnel formation. Lipid- or water-selective laser wavelengths with low absorption yield lower peak temperatures and more uniform volume heating, while lipid-selective wavelengths offer greater safety near the dermis. Ex vivo histology demonstrated greater volumetric heating with the CW, lipid-selective device at similar power settings. CONCLUSION: Wavelength, power delivery, and tip design are based on physical principles and together with treatment technique laser tunnel dimensions can be optimized as confirmed in ex vivo histology. The resulting thermal zones provide ease of penetration through adipose tissue and enable treatment uniformity. Based upon principles of fractional skin treatment the thermal zones induce healing responses in adipose tissue with potential to enhance clinical efficacy.

Semi-Automated method of analysis of horizontal histological sections of skin for objective evaluation of fractional devices.

BACKGROUND AND OBJECTIVE: The treatment of skin with fractional devices creates columns of micro-ablation or micro-denaturation depending on the device. Since the geometric profiles of thermal damage depend on the treatment parameters or physical properties of the treated tissue, the size of these columns may vary from a few microns to a few millimeters. For objective evaluation of the damage profiles generated by fractional devices, this report describes an innovative and efficient method of processing and evaluating horizontal sections of skin using a novel software program. MATERIALS AND METHODS: Ex vivo porcine skin was treated with the Lux1540/10, Lux1540 Zoom and Lux2940 with 500 optics. Horizontal (radial) sections of biopsies were obtained and processed with H&E and NBTC staining. Digital images of the histologic sections were taken in either transmission or reflection illumination and were processed using the SAFHIR program. RESULTS: NBTC- and H&E-stained horizontal sections of ex vivo skin treated with ablative and non-ablative fractional devices were obtained. Geometric parameters, such as depth, diameter, and width of the coagulated layer (if applicable), and micro-columns of thermal damage, were evaluated using the SAFHIR software. The feasibility of objective comparison of the performance of two different fractional devices was demonstrated. CONCLUSION: The proposed methodology provides a comprehensive, objective, and efficient approach for the comparison of various fractional devices. Correlation of device settings with the objective dimensions of post-treatment damage profiles serve as a powerful tool for the prediction and modulation of clinical response.