Classification of ultraviolet irradiated mouse skin histological stages by bimodal spectroscopy: multiple excitation autofluorescence and diffuse reflectance

Abstract

Histopathological analysis and in vivo optical spectroscopy were used to discriminate several histological stages of UV-irradiated mouse skin. At different times throughout the 30-week irradiation, autofluorescence (AF) and diffuse reflectance (DR) spectra were acquired in a bimodal approach. Then skin was sampled and processed to be classified, according to morphological criteria, into four histological categories: normal, and three types of hyperplasia (compensatory, atypical, and dysplastic). After extracting spectral characteristics, principal component analysis (data reduction) and the k-nearest neighbor classifying method were applied to compare diagnostic performances of monoexcitation AF (based on each of the seven excitation wavelengths: 360, 368, 390, 400, 410, 420, and 430 nm), multiexcitation AF (combining the seven excitation wavelengths), DR, and bimodal spectroscopies. Visible wavelengths are the most sensitive ones to discriminate compensatory from precancerous (atypical and dysplastic) states. Multiexcitation AF provides an average 6-percentage-point increased sensitivity compared to the best scores obtained with monoexcitation AF for all pairs of tissue categories. Bimodality results in a 4-percentage-point increase of specificity when discriminating the three types of hyperplasia. Thus, bimodal spectroscopy appears to be a promising tool to discriminate benign from precancerous stages; clinical investigations should be carried out to confirm these results.

UVA-UVB Photoprotective Activity of Topical Formulations ContainingMorinda citrifoliaExtract

“…Inflammation is one of the major histological signs of tissue damage and has been reported in other studies as an early change of the connective tissue after UV exposure [38, 39]. On the other hand, elastosis represents an actinic-induced accumulation of amorphous elastin material replacing the normal dermis, unrelated to preexisting or newly synthesized collagen [40].…”

Multidimensional spectroscopic data fusion improves precancerous tissue discrimination based on spatially resolved autofluorescence and diffuse reflectance spectroscopy

“…The validation of our approach is based on a preprocessed spectroscopic data set acquired on mice skin healthy and hyperplastic and dysplastic tissues in the framework of a preclinical UV-induced carcinogenesis study already presented in details together with the experimental set-up in Amouroux et al 1 and Diaz et al 16 . This latter data set corresponds to a multidimensional matrix containing a total of 252 tissue sites, each site being characterized by (i) seven AF intensity spectra (corresponding to seven narrow-band wavelength excitations) and shaped into Emission-Excitation Matrices (EEM), (ii) one DR spectrum (obtained for a large-band wavelength illumination) and (iii) the histological class determined by the histopathological analysis (considered as gold standard classification).…”

“…For each tissue site, these AF and DR measurements were collected in vivo at three CEFS simultaneously (CEFS1 = 271 µm, CEFS2 = 536 µm, CEFS3 = 834 µm). After excision, each tissue site was classified by the histopathologist into one of the four following classes: Healthy (H), Compensatory Hyperplasia (CH), Atypical Hyperplasia (AH) and Dysplasia (D) 1 . The total number of tissue sites in each histological reference class is: 84 H, 47 CH, 64 AH and 57 D.…”

“…Our works are focused on the combination of steady-state and spatially resolved Diffuse Reflectance (DR) spectroscopy and multiple excitation AutoFluorescence (AF) spectroscopy to improve diagnosis efficiency of skin precancerous tissues 1,10,11 . For simplicity and cost effective instrumentation considerations, steadystate excitation and spatial resolution are preferred 16 .…”

“…precancerous) modifications arise in the epidermis 1 . From the multidimensional spectroscopic measures acquired with these systems (wavelength resolved spectra, at several CEFS, AF excitations and modalities), discriminant features need to be extracted in order to best classify different precancerous states of skin tissues 1,16 . One of the difficulty is for discriminating between states showing high "confusion" between them like for instance atypical lesions 2 (that have a potential risk of progressing towards invasive lesions) and dysplasia (that is close to in situ cancer, most at risk at evolving towards invasive cancer).…”