تعيين پارامتر سطح در استاندارد پاسي (PASI) در بيماري پسوريازيس توسط پردازش تصوير

Assessment of PASI in psoriasis with image processing

Background and Objectives: Psoriasis is an auto immune skin disease which afflicts skin by the red plaques that usually are accompanied the silvery-white scales. Various medical treatments are used for this disease that have different impacts on the patients, but there is no definite cure for the disease. The PASI standard is employed to measure the effectiveness of the treatments. It includes four parameters: namely Area, Erythem, Scaliness and skin Thickness. The Area parameter in PASI standard usually is measured by physicians through subjective clinical observations, which are imprecise and boring act and in some cases it leads to diverse results. Materials and Methods: This paper presents a computer-based semiautomatic method to measure the Area parameter in PASI standard. In the proposed method, the user selects a threshold value for the Cr component in YCbCr color space to differentiate the plaques from the skin. Result: This method has the advantage over the previous methods, that is measuring of plaques with silvery-white and plaques of hairy skins and tiny plaques besides simple plaques (i.e., scale-less plaques).