## 1 Introduction  
Microdermabrasion is a mechanical and physical, controlled abrasion of the epidermis layers with a superficial effect with the use of appropriate equipment. Mainly the cells within the stratum corneum are exfoliated. The method is used in many dermatoses and skin defects. In order to achieve satisfactory and lasting results, it is necessary to perform a series of treatments [1]. Micropeeling is also used to increase the penetration of active ingredients of cosmetics, as the removal of lipophilic corneocytes facilitates the penetration of hydrophilic substances. The treatment can be performed on almost all skin types [2]. Microdermabrasion works in combination with other treatments, such as iontophoresis, sonophoresis, needle-free mesotherapy, chemical peels, and laser therapy [3]. The indications for the use of microdermabrasion are, among others: shallow wrinkles, scars, discoloration and skin laxity. Properly performed procedure has few side effects (reddening of the post-treatment area) and contraindications, which include bacterial, fungal, or viral infections at the site of the treatment, skin tumors and oncological therapy and acne vulgaris in the inflammatory stage [4]. The keratinized epidermis removal treatment can be performed using three methods that differ in the material used to exfoliate the epidermis and in the treatment intensity: diamond, corundum and water-oxygen microdermabrasion. Exfoliation of hydrophobic corneocytes from the surface of S. corneum has a multidimensional effect on the skin and has an impact on the skin's features such as its hydration, sebum production, smoothness, elasticity, permeability and absorption of radiation. The depth of exfoliation has a direct impact on the subsequent effects of the treatment [5]. Microdermabrasion and Directional Reflectance of Skin  
Electromagnetic radiation impinging on an object can be reflected, transmitted or absorbed. Which phenomenon will appear is determined by the wavelength and the physicochemical properties of the body, such as the amount of chromophores in the skin--melanin or hemoglobin. The microdermabrasion treatment, i.e., the mechanical abrasion of the stratum corneum cells, affects the physicochemical properties of the skin, which can be measured using directional-hemispherical reflectance. The directional reflectance of a surface is defined as the ratio of the total energy reflected into the subtending hemisphere to the energy incident on the studied surface. The directional reflectance may be expressed in terms of primary quantities as:  
\[\rho_{d}(\Theta_{i},\phi_{i})=\frac{\int_{0}^{2\pi}\int_{0}^{\pi/2}N_{r}\sin \Theta_{r}\cos\Theta_{r}d\Theta_{r}d\phi_{r}}{N_{i}\sin\Theta_{i}\cos\Theta_{i}d \Theta_{i}d\phi_{i}}\]  
where:  
\(\rho_{d}\) is the reflectance;  
\(\Theta_{i}\phi_{i}\) direction of energy incident on the surface;  
\(N_{i}\) is a radiance function of both position and direction, incident on the surface of an opaque object where some of the radiation is absorbed and the rest is reflected (includes diffuse reflectance or scattering)  
\(N_{r}\) is a radiance of the reflected radiation (also a function of position and direction) [6]. By measuring reflectance before and after the procedure, it can be observed how the skin parameters change, based on the data about how much radiation is reflected and how much is absorbed. The amount of energy absorbed by the skin provides information about the structure of its surface, as well as the number of chromophores it contains. The analysis of the measurement results provides information on whether there is a chromophore in the tested surface, and if so, what is its quantity. Based on the examination, the structure of the tested surface can also be assessed--if it is smooth, the radiation is absorbed more easily, but the more the structure is keratinized, granular or uneven, the easier it scatters the light. This research method can be used for assessing whether the procedure has been performed correctly and whether it is effective.