Selective photothermolysis in acne treatment: The impact of laser power.

BACKGROUND: Selective photothermolysis (SPT) using a 1726 nm laser has emerged as a safe and effective treatment option for acne vulgaris by targeting sebaceous glands (SG). Power output plays a crucial role in determining treatment selectivity and efficacy. AIMS: This work highlights the advantages of a higher-power laser source and outlines the limitations of lower-power laser sources and the subsequent impact on treatment. METHODS: Light transport and bioheat transfer simulations were performed to demonstrate photothermal impact on the SG and the surrounding dermis when irradiated by a high- or lower-power laser source. RESULTS: The simulations showed that a single higher-power-shorter-pulse (HPSP) selectively increases SG temperature well beyond bulk temperatures, which is desirable for SPT. Selectivity decreases linearly with power for the single lower-power-longer-pulses (LPLP) exposure. A multiple-LPLP approach elevates bulk temperatures significantly more than a single-pulse strategy, compromising selectivity. CONCLUSION: The goal of SPT is to damage SG safely and effectively by creating an intense temperature rise localized to the SG while moderately increasing the dermis temperature. This goal is mostly achieved with higher-power lasers that deliver a single HPSP. Lower-power lasers, longer pulse widths, and multi-pulse strategies result in higher bulk temperatures and lower SG selectivity, making such treatment challenging to execute while adding a higher risk of discomfort and downtime.

Novel 1726 nm laser demonstrates durable therapeutic outcomes and tolerability for moderate-to-severe acne across skin types.

BACKGROUND: Traditional acne management with topical therapy, systemic antibiotics, hormonal agents, or oral isotretinoin requires compliance and may produce significant side effects. However, alternative treatments with lasers had failed to demonstrate durable clearance. OBJECTIVE: To assess the tolerability and therapeutic outcomes of a novel 1726 nm laser treatment of moderate-to-severe acne across skin types. METHODS: A prospective, open-label, single-arm, Investigational Device Exemption-approved, institutional review board-approved study of 104 subjects with moderate-to-severe facial acne and Fitzpatrick Skin Types ranging from II-to-VI was conducted. Subjects received 3 laser treatments at 3 (-1/+2)-week intervals. RESULTS: Following final treatment, ≥50% reduction in active acne inflammatory lesions was 32.6% at 4-weeks follow-up, increasing further to 79.8% and 87.3% at 12 and 26-weeks, respectively. The percentage of subjects clear or almost clear increased from 0% at baseline to 9%, 36.0%, and 41.8% at 4-, 12-, and 26-weeks follow-up. No serious adverse events were observed related to device or protocol; treatments were well tolerated, requiring no anesthetic. Therapeutic outcomes and discomfort were similar across all skin types. LIMITATIONS: Lack of control group. CONCLUSIONS: The study findings demonstrate the novel 1726 nm laser is well tolerated with durable progressive posttreatment improvement to at least 26 weeks for moderate-to-severe acne across skin types.

Selective photothermolysis with a novel 1726 nm laser beam: A safe and effective solution for acne vulgaris.

BACKGROUND: Selective photothermolysis on sebaceous glands is an effective method for treating acne vulgaris (AV); however, safety, efficacy, and discomfort hinder its utilization in clinical settings. AIMS: The primary objective is to evaluate the safety and efficacy of a novel 1726 nm laser with contact cooling to treat AV. METHODS: Seventeen patients aged 18 to 36 were enrolled and treated in this IRB-approved, single-center, open-label study. Patients received up to three facial laser sessions up to seven weeks apart. Follow-up visits happened ten days post-session and at the 4 and 12 weeks following the final session. The investigator assessed the severity of device-related adverse events (AEs). Investigator Global Assessment (IGA) and inflammatory lesion counts (ILC) were used as metrics to evaluate acne resolution and skin condition enhancement. Patients' perspectives on satisfaction and comfort using this technology were assessed using Subject Experience Questionnaires (SEQ). RESULTS: Safety assessment showed mild and transient AEs. All subjects tolerated anesthetics-free treatments well, with a mean treatment discomfort score of 4.9 ± 1.5. Compared to baseline, a statistically significant reduction in ILC (p = 0.003) of 52% to 56% is achieved four to twelve weeks following treatment. Long-term follow-ups showed progressive improvement 24 months post-treatment with a 97% reduction in ILC. SEQs revealed high subject satisfaction (71%) with psychosocial improvement three months post-treatment. CONCLUSION: The novel 1726 nm laser appears safe and effective for treating mild-to-severe acne. Acne resolution is apparent within the first month and progresses beyond the study duration.

A novel 1726-nm laser system for safe and effective treatment of acne vulgaris.

Selective photothermolysis of the sebaceous glands has the potential to be an effective alternative for treating acne vulgaris. However, the translation of this technique to clinical settings has been hindered by a lack of appropriate energy sources to target sebaceous glands, concerns surrounding safety, and treatment-related discomfort and downtime. In this work, we introduce the first FDA-approved system that combines a 1726-nm laser and efficient contact cooling to treat mild, moderate, and severe acne effectively while ensuring safety and minimal patient discomfort without adjunct pain mitigation techniques. Light transport and bioheat transfer simulations were performed to demonstrate the system's efficacy and selectivity. The resulting thermal damage to the skin and sebaceous glands was modeled using the Arrhenius kinetic model. Numerical simulations demonstrated that combining laser energy and optimal contact cooling could induce a significant temperature increase spatially limited to the sebaceous gland; this results in highly selective targeting and maximum damage to the sebaceous gland while preserving other skin structures. In vivo human facial skin histology results corroborated the simulation results. The studies reported here demonstrate that the presented 1726-nm laser system induces selective photothermolysis of the sebaceous gland, providing a safe and effective method for the treatment of acne vulgaris.

Picture-based acne lesion counts: A validation study to assess accuracy and reliability of acne lesion counts via photography.

BACKGROUND: Acne lesion counting (ALC) is widely used to evaluate efficacy of new acne treatments. Although such evaluations are precise and highly discriminative, if assessed live, it can be a time-consuming and intrusive measurement. Photographic assessment is a viable mode for ALCs and for training and/or qualifying evaluators. AIMS: The purpose of this study was to validate photographic methods for performing ALCs and to provide an objective measurement tool to train and/or qualify lesion count evaluators for deployment in both small- and large-scale studies. PATIENTS/METHODS: Assess accuracy and reliability of acne lesion counting via photographic methods in 8 subjects aged 16 to 40 years, with Fitzpatrick Skin Types I to VI. Frontal and 45°angle images taken at the single in-clinic visit. Each subject underwent 3 counts per 4 evaluators: 1 set of live counts and 2 sets of photo counts. Intra-evaluator and inter-evaluator reliability measures for photo counts were evaluated using calculations of intraclass correlation coefficients (ICCs). RESULTS: Eight subjects (2 males and 6 females) age between 16 and 40 (min 16 years, max 25 years) diagnosed with facial acne vulgaris participated in the study. Fitzpatrick Skin Types ranged from III to V (three Type-III, four Type-IV, and one Type-V). ICC values for intra-evaluator reliability were found to be >0.95 for each evaluator, and ICC for inter-evaluator reliability was found to be 0.98. CONCLUSIONS: Photographic lesion count methodology is a reliable and accurate tool for objective measurement of ALCs and additionally, for training and/or qualifying evaluators.

Hyperthermic injury to adipocyte cells by selective heating of subcutaneous fat with a novel radiofrequency device: feasibility studies.

BACKGROUND AND OBJECTIVE: The main objective of the present study is to demonstrate the feasibility of utilizing a novel non-invasive radiofrequency (RF) device to induce lethal thermal damage to subcutaneous adipose tissue only by establishing a controlled electric field that heats up fat preferentially. STUDY DESIGN/MATERIALS AND METHODS: Adipocyte cells in six-well plates were subjected to hyperthermic conditions: 45, 50, 55, 60, and 65 degrees C during 1, 2, and 3 minutes. Cell viability was assessed 72 hours after exposure. Two groups of abdominoplasty patients were treated with the RF device during and days before their surgical procedure. Temperatures of cutaneous and subcutaneous tissues were measured during treatment (3 minutes) of the first group. The immediate tissue response to heating was assessed by acute histology. The delayed tissue response was assessed by histology analysis of the second group, 4, 9, 10, 17, and 24 days after treatment (22 minutes). A mathematical model was used to estimate treatment temperatures of the second group. The model uses patient-based diagnostic measurements as input and was validated with in vivo clinical temperature measurements. RESULTS: Cell viability dropped from 89% to 20% when temperature increased from 45 to 50 degrees C during 1 minute exposures. Three minutes at 45 degrees C resulted in 40% viability. In vivo, the temperature of adipose tissue at 7-12 mm depth from the surface increased to 50 degrees C while the temperature of cutaneous tissues was <30 degrees C during RF exposure. Acute and longitudinal histology evaluations show normal epidermal and dermal layers. Subcutaneous tissues were also normal acutely. Subcutaneous vascular alterations, starting at day 4, and fat necrosis, starting at day 9, were consistently observed within 4.5-19 mm depth from the skin surface. Subcutaneous tissue temperatures were estimated to be 43-45 degrees C for 15 minutes. CONCLUSIONS: A controlled internal electric field perpendicular to the skin-fat interface is selective in heating up fat and, consequently, has the ability to induce lethal thermal damage to subcutaneous adipose tissues while sparing overlying and underlying tissues. In vitro adipocyte cells are heat sensitive to thermal exposures of 50 and 45 degrees C on the order of minutes, 1 and 3 minutes, respectively. In vivo, 15 minutes thermal exposures to 43-45 degrees C result in a delayed adipocyte cellular death response-in this study, 9 days. The novel RF device presented herein effectively delivers therapeutic thermal exposures to subcutaneous adipose tissues while protecting epidermal and dermal layers.

Controlled volumetric heating of subcutaneous adipose tissue using a novel radiofrequency technology.

BACKGROUND AND OBJECTIVE: The objective of the present study was to demonstrate the feasibility of varying the size of the heating volume of subcutaneous adipose tissue using a novel radiofrequency (RF) technology that controls the delivered energy distribution on the skin surface. STUDY DESIGN/MATERIALS AND METHODS: Changes in the distribution of the electric potential at the skin surface due to frequency adjustment of a novel RF device were experimentally characterized on human skin at 500 kHz, 1, 2, 3, and 4 MHz. These measurements were used to model RF-induced electric fields and power absorption. Thermal measurements in ex vivo animal models were used to complement the initial mathematical modeling. RESULTS: At 500 kHz the electric potential on the skin surface was nearly constant across the RF applicator surface. At 4 MHz the electric potential dropped 30% from the center to the edge of the RF applicator. At the centerline of the RF applicator, modeling shows that within a 3 cm subcutaneous fat layer the absorbed power at the bottom layer was 40% less than that at the top for 500 kHz. The absorbed power decreased 80% for 4 MHz. Temperature measurements show uniform heating across a horizontal array of probes with 500 kHz. Temperatures were significantly higher at the center probes for 4 MHz. Cross-sectional radiometric temperature maps show a larger heated tissue cross-section using 500 kHz as opposed to 4 MHz. CONCLUSIONS: As the frequency increases (i) the electric potential at the skin surface decreases from the center to the edge of the RF applicator; (ii) the difference between the power absorbed at the top and bottom of the subcutaneous fat layer increases; (iii) the difference between the power absorbed at the center and the periphery of the exposed subcutaneous fat volume also increases; and, consequently, (iv) the size of the heated subcutaneous fat volume decreases. Such a device when used in humans may allow for differential delivery of heat to varying fat thicknesses and anatomic areas.