Estimation of Biological Parameters of Cutaneous Ulcers Caused by Leishmaniasis in an Animal Model Using Diffuse Reflectance Spectroscopy

Abstract

Cutaneous leishmaniasis (CL) is a neglected tropical disease that requires novel tools for its understanding, diagnosis, and treatment follow-up. In the cases of other cutaneous pathologies, such as cancer or cutaneous ulcers due to diabetes, optical diffuse reflectance-based tools and methods are widely used for the investigation of those illnesses. These types of tools and methods offer the possibility to develop portable diagnosis and treatment follow-up systems. In this article, we propose the use of a three-layer diffuse reflectance model for the study of the formation of cutaneous ulcers caused by CL. The proposed model together with an inverse-modeling procedure were used in the evaluation of diffuse-reflectance spectral signatures acquired from cutaneous ulcers formed in the dorsal area of 21 golden hamsters inoculated with Leishmanisis braziliensis. As result, the quantification of the model’s variables related to the main biological parameters of skin were obtained, such as: diameter and volumetric fraction of keratinocytes, collagen; volumetric fraction of hemoglobin, and oxygen saturation. Those parameters show statistically significant differences among the different stages of the CL ulcer formation. We found that these differences are coherent with histopathological manifestations reported in the literature for the main phases of CL formation.

Diffuse Reflectance Parameters of Treated Leishmaniasis Cutaneous Ulcers and Association with Histopathologies in an Animal Model: A Proof of Concept

“…1. PMN versus diameter of collagen: According to a previous study, 31 a higher diameter of collagen is related to the formation of granulomas. Collagen production allows connective tissue matrices to emerge.…”

“…In our case, the system was composed of a 150 W QTH lamp (66088 Fiber Optic Illuminator, 150 W QTH, Oriel Instruments, Newport Corporation, Irvine, CA) with a liquid light guide (LLG) (OSL1–High-Intensity Fiber Light Source from THORLABS, Newton, NJ), an optical fiber (OF) with a core diameter of 300 µm (P300-1-SR from Ocean Optics, Largo, FL) connected to a spectrometer with a charge-coupled device (CCD) detector (HR4C3337 from Ocean Optics), and a computer with dedicated software installed (Ocean View from Ocean Optics). 31 The LLG and OF were coupled to a single probe to accomplish requirements as suggested by the American Society for Testing and Materials. 32 In this probe, in order to collect the reflected light, the OF was connected to a collimator lens.…”

“…Spectral signatures were calibrated and filtered according to the procedure described by Botina et al 31 For calibration, we used white and black diffuse reflectance standards, which reflect more than 99% and less than 2% of the light, respectively. Then, calibrated spectra were compared against an acceptance range to eliminate outliers and obtain only 10 diffuse reflectance spectra per hamster.…”

“…After that, the chosen spectra were filtered through a digital median filter to reduce noise. More information about this procedure can be found in the article by Botina et al 31…”

“…For the purposes of this article, a diffuse reflectance model 31,33,34 has been used. In this model, the diffuse reflectance of a semi-infinite turbid medium is expanded into three parts, each one representing the three main layers of the skin: epidermis, dermis, and hypodermis.…”