Abstract
In this paper we present three studies that demonstrate the applicability of spectroscopy methods and optical clearing treatments in pathology identification and monitoring. In the first study, by obtaining the absorption spectra of human healthy and pathological (adenocarcinoma) colorectal mucosa tissues, it was possible to identify a higher content of a pigment in the diseased tissues. This study also shows that machine learning methods can be used to reach the same differentiated results in vivo through diffuse reflectance spectroscopy. In the second study, the combination of collimated transmittance spectroscopy with optical clearing treatments allowed to obtain the diffusion coefficients of glucose in healthy and pathological colorectal mucosa as: D glucose =5.8x 10 – 7 cm 2 /s and D glucose =4.4x 10 – 7 cm 2 /s, respectively. This study also demonstrated that the diseased tissues contains about 5% more mobile water than the healthy tissues. The third study was performed to evaluate the protein dissociation mechanism of optical clearing. By treating both healthy and pathological colorectal mucosa tissues with 93%-glycerol, a protein dissociation rate of about 3 times higher was obtained for the pathological mucosa. All the discriminating parameters that result from these studies can be obtained in the in vivo situation through diffuse reflectance spectroscopy and further studies to evaluate their values in different stages of cancer progression are of great importance to develop disease monitoring protocols.
Highlights
Current diagnostic of oncologic malignancies relies on imaging methods that use ionizing radiation [1]
The optical methods used in the studies of most of these publications are basically included in two groups: spectroscopy methods, which include optical, Raman, light scattering, near infrared and fluorescence, and imaging methods, which include optical coherence tomography (OCT), fluorescence microscopy, laser scanning microscopy and confocal microscopy
The results obtained in the above studies show that it is possible to discriminate colorectal cancer through optical spectroscopy methods
Summary
Current diagnostic of oncologic malignancies relies on imaging methods that use ionizing radiation [1] Such procedures present a great number of disadvantages, since ionizing radiation can induce, among others, DNA double-strand breaking [2, 3] and cell death in surrounding healthy tissues [4, 5]. To avoid such side effects of ionizing radiation, biophotonics suggests alternative optical methods that, by the harmless use of light, can perform reliable and noninvasive diagnostic procedures. An additional fact is that any therapeutic procedure to eliminate cancer becomes ineffective when the diagnosis is established at a later stage of progression, which is the most common case [1, 18]
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