{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T01:52:25Z","timestamp":1777513945111,"version":"3.51.4"},"reference-count":41,"publisher":"AIP Publishing","issue":"5","funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["FCT-UIDB\/04730\/2020"],"award-info":[{"award-number":["FCT-UIDB\/04730\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Government of the Russian Federation","award":["2020-220-08-2389"],"award-info":[{"award-number":["2020-220-08-2389"]}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2021,5,1]]},"abstract":"<jats:p>In this study, we used machine learning techniques to reconstruct the wavelength dependence of the absorption coefficient of human normal and pathological colorectal mucosa tissues. Using only diffuse reflectance spectra from the ex vivo mucosa tissues as input to algorithms, several approaches were tried before obtaining good matching between the generated absorption coefficients and the ones previously calculated for the mucosa tissues from invasive experimental spectral measurements. Considering the optimized match for the results generated with the multilayer perceptron regression method, we were able to identify differentiated accumulation of lipofuscin in the absorption coefficient spectra of both mucosa tissues as we have done before with the corresponding results calculated directly from invasive measurements. Considering the random forest regressor algorithm, the estimated absorption coefficient spectra almost matched the ones previously calculated. By subtracting the absorption of lipofuscin from these spectra, we obtained similar hemoglobin ratios at 410\/550\u2009nm: 18.9-fold\/9.3-fold for the healthy mucosa and 46.6-fold\/24.2-fold for the pathological mucosa, while from direct calculations, those ratios were 19.7-fold\/10.1-fold for the healthy mucosa and 33.1-fold\/17.3-fold for the pathological mucosa. The higher values obtained in this study indicate a higher blood content in the pathological samples used to measure the diffuse reflectance spectra. In light of such accuracy and sensibility to the presence of hidden absorbers, with a different accumulation between healthy and pathological tissues, good perspectives become available to develop minimally invasive spectroscopy methods for in vivo early detection and monitoring of colorectal cancer.<\/jats:p>","DOI":"10.1063\/5.0052088","type":"journal-article","created":{"date-parts":[[2021,5,17]],"date-time":"2021-05-17T15:58:33Z","timestamp":1621267113000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":20,"title":["Diffuse reflectance and machine learning techniques to differentiate colorectal cancer <i>ex vivo<\/i>"],"prefix":"10.1063","volume":"31","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8306-3362","authenticated-orcid":false,"given":"Lu\u00eds","family":"Fernandes","sequence":"first","affiliation":[{"name":"Center for Innovation in Engineering and Industrial Technology, Polytechnic of Porto\u2014School of Engineering 1 , 4249-015 Porto, Portugal"},{"name":"Physics Department, Polytechnic of Porto\u2014School of Engineering 2 , 4249-015 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1925-5081","authenticated-orcid":false,"given":"S\u00f3nia","family":"Carvalho","sequence":"additional","affiliation":[{"name":"Department of Pathology and Cancer Biology and Epigenetics Group-Research Center, Portuguese Oncology Institute of Porto 3 , 4200-072 Porto, Portugal"},{"name":"Department of Pathology, Santa Luzia Hospital, ULSAM 4 , 4904-858 Viana do Castelo, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0561-3880","authenticated-orcid":false,"given":"Isa","family":"Carneiro","sequence":"additional","affiliation":[{"name":"Department of Pathology and Cancer Biology and Epigenetics Group-Research Center, Portuguese Oncology Institute of Porto 3 , 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3171-4666","authenticated-orcid":false,"given":"Rui","family":"Henrique","sequence":"additional","affiliation":[{"name":"Department of Pathology and Cancer Biology and Epigenetics Group-Research Center, Portuguese Oncology Institute of Porto 3 , 4200-072 Porto, Portugal"},{"name":"Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar-University of Porto (ICBAS-UP) 5 , 4050-313 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7479-2694","authenticated-orcid":false,"given":"Valery V.","family":"Tuchin","sequence":"additional","affiliation":[{"name":"Science Medical Center, Saratov State University 6 , Saratov 410012, Russia"},{"name":"Interdisciplinary Laboratory of Biophotonics, National Research Tomsk State University 7 , Tomsk 634050, Russia"},{"name":"Laboratory of Laser Diagnostics of Technical and Living Systems, Institute of Precision Mechanics and Control of the Russian Academy of Sciences 8 , Saratov 410028, Russia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6193-8540","authenticated-orcid":false,"given":"H\u00e9lder P.","family":"Oliveira","sequence":"additional","affiliation":[{"name":"Institute for Systems and Computer Engineering, Technology and Science, INESC TEC 9 , 4200-465 Porto, Portugal"},{"name":"Faculty of Science, University of Porto, FCUP 10 , 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0667-3428","authenticated-orcid":false,"given":"Lu\u00eds M.","family":"Oliveira","sequence":"additional","affiliation":[{"name":"Center for Innovation in Engineering and Industrial Technology, Polytechnic of Porto\u2014School of Engineering 1 , 4249-015 Porto, Portugal"},{"name":"Physics Department, Polytechnic of Porto\u2014School of Engineering 2 , 4249-015 Porto, Portugal"}]}],"member":"317","published-online":{"date-parts":[[2021,5,17]]},"reference":[{"key":"2023071502352232500_c1","doi-asserted-by":"publisher","first-page":"R37","DOI":"10.1088\/0031-9155\/58\/11\/R37","article-title":"Optical properties of biological tissues: A review","volume":"58","year":"2013","journal-title":"Phys. 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