Quantifying skin photodamage with spatial frequency domain imaging: statistical results

Abstract

We investigated the change in optical properties and vascular parameters to characterize skin tissue from mild photodamage to actinic keratosis (AK) with comparison to a published photodamage scale. Multi-wavelength spatial frequency domain imaging (SFDI) measurements were performed on the dorsal forearms of 55 adult subjects with various amounts of photodamage. Dermatologists rated the levels of photodamage based upon the photographs in blinded fashion to allow comparison with SFDI data. For characterization of statistical data, we used artificial neural networks. Our results indicate that optical and vascular parameters can be used to quantify photodamage and can discriminate between the stages as low, medium, and high grades, with the best performance of ∼70%, ∼76% and 80% for characterization of low- medium- and high-grade lesions, respectively. Ultimately, clinicians can use this noninvasive approach for risk assessment and frequent monitoring of high-risk populations.

Fig. 1.

(a) Dermatologists’ clinical scores of skin damage. (b) Range of scores from dermatologists. (c) Examples of mild, moderate, severe photodamage analyzed by clinical dermatologists.

Fig. 2.

(a) Schematic diagram and (b) photo of SFDI instrument for imaging lesions on arm.

Fig. 3.

(a), (b), (c) Absorption imaging maps and the (e), (f), (g) reduced scattering maps for three subjects at 490 nm. Red arrows highlight the visible lesion for subject with severe photodamage (P3). (d) Histograms of the absorption parameter and the (h) reduced scattering parameter for the subjects with mild (P1), moderate (P2), and severe damage (P3) at 490 nm.

Fig. 4.

Separation of groups possible with respect to (a) scattering power, B (b) deoxy-hemoglobin concentration, C_deoxy (c) total hemoglobin concentration, THC.