Characterization of port wine stain skin erythema and melanin content using cross‐polarized diffuse reflectance imaging

Abstract

Background and Objectives: Objective methods to assess quantitatively port wine stain (PWS) blanching in response to laser therapy are needed to improve laser therapeutic outcome. Previous studies have attempted to assess objectively PWS color based on point measurement devices. To date, these approaches have typically been limited by a number of factors such as small test area and need for contact. To address these issues, a cross-polarized diffuse reflectance imaging system and color image analysis method has been developed to evaluate quantitatively erythema and melanin content in PWS skin. Study Design/Materials and Methods: A cross-polarized diffuse reflectance system has been constructed to acquire high resolution digital images while minimizing artifacts such as glare, shadowing, and nonuniform illumination effects that can compromise image fidelity. Furthermore, an image analysis algorithm has also been developed to analyze normal and PWS skin in terms of CIEL*a*b* color space parameters. Using the algorithm, images of color space intensity, L*, and saturation, a*, indices have been calculated to extract quantitative metrics of melanin and erythema, respectively. Results: Compared to the cross-polarized diffuse reflectance image, the a* index image enhanced the contrast in regions of high and low erythema and seems to have quasi correlation with the L* index image. In the presented PWS patient example, the relative a* index difference (Da*) image showed less erythema in PWS skin after laser treatment when compared to pre-treatment values. Conclusions: Our cross-polarized imaging system and color image analysis method is a simple, noncontact technique that can indirectly provide quantitative measurement of erythema and melanin content in PWS skin.

Reduction of shading-derived artifacts in skin chromophore imaging without measurements or assumptions about the shape of the subject

“…26 Also, in aesthetic evaluations in dermatology and cosmetology, evaluations of each body part (especially the face) as a whole are important. 27 The robustness of this method against fluctuations in the intensity of the light source provide a practical advantage.…”

Description and Analysis of Treatments for Port-wine Stain Birthmarks

“…A digital color camera (DiMAGE7; Minolta Co, Osaka, Japan) was used to acquire images. 23 A macro ring flash (model 1200; Minolta Co) controlled by a flash controller provided shadowless, uniform illumination. Glare was reduced from the skin surface by using a linear polarizer (model A45-669; Edmund Industrial Optics, Barrington, NJ) placed in front of the macro ring flash; a second cross-polarizer was placed in front of the camera lens.…”

“…Additional optical instruments under development for PWS skin diagnostics and therapy evaluation include videomicroscopy, 37 modulated imaging, 38 cross-polarized diffuse reflectance imaging, 23 and laser speckle imaging. 39 Laser speckle imaging is of particular interest because it can serve as a relatively low-cost, wide-field, vascular imaging instrument to evaluate skin perfusion dynamics intraoperatively.…”

Model-based Skin Pigment Cartography by High-Resolution Hyperspectral Imaging

“…Non-invasive imaging systems of the skin are used in a wide range of clinical applications in the last decades, in particular in order to get information on pigmentation disorders: melanin index, port wine vein, vitiligo, erythema [4][5]… Since pigmentation determines the spectral reflectance of the skin, the best way to observe it is to make images in different spectral bands, either in three wide spectral bands as in classical RGB imaging [6][7], or in more than 10 short spectral bands as in multispectral imaging [8][9]. There already exist several multispectral imaging instruments for skin observation on the marketplace (e.g.…”