Treatment of seborrheic keratosis with a copper vapour laser

Aim: to assess the efficacy and side-effect risk of the surgical treatment of seborrheic k eratosis (SK) using a copper vapour laser (CVL).Patients and methods. 3980 patients (1214 men and 2766 women aged 20 to 78 years) suffering from SK were treated using a CVL (Yakhroma-Med model, Russian producer) equipped with a laser pen and a scanning nozzle. The laser treatment was performed without anaesthesia in one to four sessions. During the treatment procedure, the following radiation parameters were applied: wavelengths ranging from 511 to 578 nm (in the ratio of 3 to 2), an average power of 0.6–1.2 W and an exposure duration ranging from 0.2 to 0.4 s. The diameter of the light spot on the skin surface was 1 mm. The follow-up observation lasted 24 months.Results. The computer simulation of tissue heating by CVL and other laser systems showed that CVL is an optimal treatment choice for seborrheic keratosis in terms of the energy deposition depth. According to our clinical data and the results of computer simulation, the CVL is established to be the safest and the most effective for seborrheic keratosis treatment.

Treatment of basal cell cancer in the periorbital area using a pulsed copper vapour laser

An increase in life expectancy in developed countries is inevitably accompanied by an increase in the number of nonmelanoma skin diseases, which are primarily represented by basal cell cancer (BCC) occurring in elderly and old-age patients. The pathogenesis of such diseases is associated both with impaired proliferation and differentiation of the keratinocytes of the epidermal basal layer, as well as with the transformation of the vasculature in the papillary dermis in the vicinity of BCC. In recent years, such conditions have been increasingly treated using CO2 , neodymium, diode and pulsed-dye lasers. In many cases, these devices allow malignant BCC cells to be successfully eliminated. However, the use of near-infrared lasers in the periorbital area is limited due to a higher risk of damaging the organs of the visual system. Therefore, a search for new laser surgery methods that can be used for treating malignant skin tumours seems to be a prospective research direction.Methods. 3 male and 9 female patients diagnosed with primary BCC were treated using a copper vapour laser (Yakhroma-Med). The age of the patients varied from 34 to 77 years. Laser treatment was carried out in one session under the following irradiation parameters: the wavelength of 511 and 578 nm, the average power of up to 3 W and a series of 15 ns pulses. The pause between the pulses was 60 μs, with the exposure time ranging from 200 to 600 ms. The light spot diameter on the skin surface was 1 mm. The follow-up monitoring duration was 24 months.Results. In all the BCC patients, one session of copper vapour laser treatment allowed malignant cells in the disease area to be completely eliminated without relapses during 2 years after the therapy. The duration of skin healing in the irradiated area was 2 weeks in patients under the age of 40 years, compared to 3–4 weeks in elderly patients. After the treatment, short-term side effects, such as a slight edema, erythema and peeling, were observed.

The induction pumping of Coaxial Lasers on Self-Terminating Transitions

The paper presents the results of the numerical simulations of pumping a copper vapour laser by a repetitively pulsed induction (electrodeless) discharge. We have investigated the version of the laser with an annular discharge volume formed by two coaxial cylinders. Such coaxial chamber is shown to be more appropriate for the induction pumping than the conventional cylindrical chamber. In the first case, higher coupling factors in the transformercoupled circuit of the induction discharge as well as rather high curl electric field are achieved. Moreover, from the ecological point of view, the coaxial chamber appears to be safer for the surrounding personnel in terms of their exposure to electromagnetic radiation. The present work briefly presents the physical model of the laser which describes the dynamics of the plasma parameters, the kinetics of the inverse population of the working levels for the laser on self terminating transitions as well as the development of the induction radiation. The paper also presents the electrical equations describing the simplest source of electrical pump pulses. The thermal characteristics of the working medium are estimated and the design calculations of the chamber are performed. The numerical experiments have found that, in contrast to the case of a conventional copper vapour laser with aperiodic discharge, in the regarded versions of the copper vapour laser the pump pulse is realized as a train of high-frequency damped oscillations. The analysis of the physical processes occurring in the plasma of the high-frequency discharge is carried out. The pulsed behaviour of the Joule heat power is shown to release results in pronounced pulsations of the electron temperature. This fact, however, does not significantly affect the operation of the laser on self-terminating transitions. In the optimal pumping regimes, subtle oscillations are merely observed for the inverse population of the copper atom working levels and for the intensity in the radiation pulse. High output laser characteristics achieved in the numerical simulations demonstrate the potential for efficient pumping of the copper vapour laser using the inductive method which is new for such lasers.