Abstract
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. 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. 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 (Deltaa*) image showed less erythema in PWS skin after laser treatment when compared to pre-treatment values. 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.
Highlights
Port wine stains (PWS) are congenital hypervascular cutaneous malformations that occur typically on the face and neck
Previous studies have demonstrated that clinical judgment of port wine stain (PWS) skin appearance before and after laser treatment is strongly correlated with skin erythema [9,10]
The RGB data is subsequently converted to the Commission Internationale de l’Eclairage (CIE) L*a*b* color space (Table 1), which consists of three values: L* describes the reflected light intensity and varies from 0 to 100; a* describes color saturation and varies from À60 for green to þ60 for red; and b* describes color saturation and varies from À60 for blue to þ60 for yellow [15]
Summary
Port wine stains (PWS) are congenital hypervascular cutaneous malformations that occur typically on the face and neck. Previous studies have demonstrated that clinical judgment of PWS skin appearance before and after laser treatment is strongly correlated with skin erythema [9,10] Commercial devices, such as reflectance spectrophotometers and tristimulus colorimeters, can provide quantitative information on skin erythema and melanin. 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. 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.
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