Determination of optimal view angles for quantitative facial image analysis

Byungjo Jung,Bernard Choi,J Stuart Nelson,Anthony J Durkin,Yongjin Shin

doi:10.1117/1.1895987

Byungjo Jung, Bernard Choi + Show 3 more

Open Access

https://doi.org/10.1117/1.1895987

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Abstract

In quantitative evaluation of facial skin chromophore content using color imaging, several factors such as view angle and facial curvature affect the accuracy of measured values. To determine the influence of view angle and facial curvature on the accuracy of quantitative image analysis, we acquire cross-polarized diffuse reflectance color images of a white-patched mannequin head model and human subjects while varying the angular position of the head with respect to the image acquisition system. With the mannequin head model, the coefficient of variance (CV) is determined to specify an optimal view angle resulting in a relatively uniform light distribution on the region of interest (ROI). Our results indicate that view angle and facial curvature influence the accuracy of the recorded color information and quantitative image analysis. Moreover, there exists an optimal view angle that minimizes the artifacts in color determination resulting from facial curvature. In a specific ROI, the CV is less in smaller regions than in larger regions, and in relatively flat regions. In clinical application, our results suggest that view angle affects the quantitative assessment of port wine stain (PWS) skin erythema, emphasizing the importance of using the optimal view angle to minimize artifacts caused by nonuniform light distribution on the ROI. From these results, we propose that optimal view angles can be identified using the mannequin head model to image specific regions of interest on the face of human subjects.

Highlights

Assessment of skin chromophoremelanin and hemoglobincontent is important to identify the presence of cutaneous pathology or to monitor patient response to therapeutic intervention of skin disease
To simulate different regions of interestsROIson the face, optimal view angles were determined for various subsets of the 50 white patches placed on the mannequin head model
Our results indicate that view angle and facial curvature affect quantitative measurement of facial skin erythema

Summary

Introduction

Assessment of skin chromophoremelanin and hemoglobincontent is important to identify the presence of cutaneous pathology or to monitor patient response to therapeutic intervention of skin disease. Quantitative point-measurement devices, such as reflectance spectrophotometers and tristimulus colorimeters, have been employed to estimate the content of melanin and hemoglobin in human skin.[1,2,3,4,5] The clinical usefulness of spectrophotometers and colorimeters is limited by practical considerations such as small test area, potential skin blanching due to probe contact, poor spatial resolutionmeasurements are typically resolved on a spatial scale equivalent to the dimensions of the probe head, and difficulty in relocating the probe to the same site over the longitudinal course of therapy, which may have a duration of years.

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