Yamamoto Tadamasa, Takiwaki Hirotsugu, Arase Seiji, Ohshima Hiroshi
Department of Dermatology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
Skin Res Technol. 2008 Feb;14(1):26-34. doi: 10.1111/j.1600-0846.2007.00256.x.
Quantification of erythema and pigmentation is useful for analysis of skin tests and management of skin diseases. However, reflectance instruments for this purpose suffer from many technical and financial disadvantages. The aim of this study was to establish a method for evaluation of the amounts of haemoglobin and melanin using ordinary digital cameras and Image J freeware.
Based on the theories on the absorbance of a multilayered skin model, the erythema index (EI) and melanin index (MI) images were derived by image processing from digital colour images of the skin, which were obtained with four kinds of digital cameras. The specificity of these indices and the linearity between index values and the amounts of haemoglobin and melanin were determined by using images of various concentrations of haemoglobin and melanin solutions. The accuracy of both types of index images was also examined by comparing the index values of UV-induced erythema and pigmentation of various intensities with those measured with a reflectance spectrophotometer.
The specificity of EI and MI images was good as little interference was noted with each other. The linearity between EI and haemoglobin concentration, as well as that between MI and melanin concentration was excellent. For UV-induced erythema and pigmentation, good linear correlation was confirmed between two types of EI obtained by the two methods, as well as between two types of MI. However, the index values derived from digital images depended on the camera used as well as on the circumstantial conditions, such as the distance from objects and illumination.
EI and MI images are reliable and useful for quantifying erythema and pigmentation, if obtained under constant and consistent conditions. Apart from financial benefits, this method has many advantages and greater clinical utility in comparison with reflectance instruments.
红斑和色素沉着的量化对于皮肤试验分析和皮肤病管理很有用。然而，用于此目的的反射仪器存在许多技术和经济上的缺点。本研究的目的是建立一种使用普通数码相机和Image J免费软件评估血红蛋白和黑色素含量的方法。
基于多层皮肤模型吸光度的理论，通过图像处理从皮肤的数字彩色图像中得出红斑指数（EI）和黑色素指数（MI）图像，这些数字彩色图像是用四种数码相机获得的。通过使用不同浓度的血红蛋白和黑色素溶液的图像来确定这些指数的特异性以及指数值与血红蛋白和黑色素含量之间的线性关系。还通过比较不同强度紫外线诱导的红斑和色素沉着的指数值与用反射分光光度计测量的值来检查两种类型指数图像的准确性。
EI和MI图像的特异性良好，彼此之间干扰很小。EI与血红蛋白浓度之间以及MI与黑色素浓度之间的线性关系非常好。对于紫外线诱导的红斑和色素沉着，通过两种方法获得的两种类型的EI之间以及两种类型的MI之间均证实了良好的线性相关性。然而，从数字图像得出的指数值取决于所使用的相机以及诸如与物体的距离和光照等环境条件。
如果在恒定且一致的条件下获得，EI和MI图像对于量化红斑和色素沉着是可靠且有用的。与反射仪器相比，该方法除了具有经济优势外，还有许多优点和更大的临床实用性。
