Applications in light-induced spectroscopy with violet LED lamp: autofluorescence

Abstract

The early detection of a neoplastic disease, as well as the development of more efficient treatments, are crucial for improving the survival rate. A variety of new and emerging diagnostic strategies based on spectroscopic techniques such as non-invasive one-point fluorescence (PF) detection, are available to improve the screening procedure [1,2]. PF technique provides useful information for monitoring the evolution of the abundance and distribution of endogenous fluorophores associated with the neoplastic disease in low-pigmented superficial neoplasia [3,4]. The main objective of the present study was to develop a violet LED light source suitable for medical application devoted to the diagnostic and treatment of non-melanoma skin cancers. For this propose, we constructed a 12 W violet LED lamp (with maximum emission peak at 405 nm) made up of four mobile 3 W LED, each one coupled to a heat sink and a lens and mounted on a platform with adjustable screws. The power supply allows the modification of the intensity of illumination. The LED lamp was characterized employing a spectrometer coupled to an optical fiber. The irradiance for different distances between the lamp and the detector was assessed. Furthermore, the radiant power and the radiant intensity were evaluated. Data were compared with a simulated LED lamp by using the Zemax optic software for the realization of luminaries with the desired characteristics and modes of operation to deliver the energy density at the interest point, as required for medical applications. The developed lamp in combination with a portable spectrometer was employed under medical supervision to detect differences in the emission spectrum of skin suspicious regions and healthy ones located at the head of a patient with non-melanoma skin cancer. The light of the LED lamp was concentrated in the examined region by means of the proper focusing of the four individual LEDs, rendering a high intensity homogeneous spot. Thus, endogenous chromophores at the skin were excited, and the emission intensity appeared to be enough to detect an enhanced peaked structure around 600 nm for some suspicious regions before treatment, and that were absence in healthy regions. These differences can be related to the augmented protoporphyrin IX content in neoplastic regions. Results presented in this work indicate the usefulness of the developed and characterized LED lamp as an easy-to-use device for the non-invasive detection of skin neoplastic pathologies, before and after treatment, with the aim of better define the malignant regions as well as predict the outcome of a certain treatment.