Quantification of scalp hair--a computer-aided methodology.

A method for obtaining a quantitative assessment of hair density is described. First, a photographic image of the scalp is digitized onto a high-resolution computer graphics screen. Second, the frequency of each of 256 gray levels (one for each of 500 vertical X 500 horizontal = 250,000 locations on the screen) is obtained and the frequency histogram of gray levels is displayed. Third, a statistical procedure, gaussian mixture analysis, is used to resolve the frequency distribution into two normally distributed component distributions. The first component distribution describes the range of gray levels that are typically associated with hair. The second component distribution describes shades of gray that are typically associated with scalp. The statistical model provides a precise measure of the proportion of the head that exhibits gray levels in each of the two component distributions (hair or scalp). The proportion of the first component distribution is a scale-independent measure of hair density. The difference in this quantity before and after treatment provides an accurate quantitative determination of the change in hair density and hence of the efficacy of treatment.