Irregularity skin index (ISI): a tool to evaluate skin surface texture.
OBJECTIVE
Irregularity of skin surface microtopography is difficult to evaluate in Euclidean geometry. Using a fast Fourier transform (FFT), it is possible to convert a space field into a frequency field and to obtain quantitative evaluation of this important feature of the skin. The aim of the present study was to test the applicability of a new parameter, derived from computer assisted FFT, to skin texture, in order to quantify its irregularity. This parameter has the additional advantage of being anisotropic.


METHODS
The study was conducted on 50 female volunteers. Skin replicas were performed on a healthy area that was not chronically photo-exposed. A new parameter, called "irregularity skin index" (ISI), was identified from FFT. The correlation with volunteers' age was calculated.


RESULTS
ISI was calculated by FFT in two different directions (referred to the x and y axis of the diagram of the FFT and named, respectively, ISIomegax and ISIomegay). The irregularity skin indexes increased with age of the subjects, showing a correlation with age of r=0.47 (ISIomegax) and r=0.51 (ISIomegay).


CONCLUSIONS
By showing a relatively good correlation with age, ISI seems to be a promising parameter for the study of ageing skin.
Setaro
M
M
DermIng, Institute of Dermatological Research and Bioengineering, Milan, Italy.
Sparavigna
A
A
D000328:Adult; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008875:Middle Aged; D008953:Models, Anatomic; D008954:Models, Biological; D012826:Silicone Elastomers; D012867:Skin / Q000648:ultrastructure*; D013499:Surface Properties
D012826:Silicone Elastomers