Study of paraffin-embedded colon cancer tissue using terahertz spectroscopy Faustino Wahaia a,⇑ , Irmantas Kasalynas b , Dalius Seliuta b , Gediminas Molis c , Andrzej Urbanowicz c,d , Catia D. Carvalho Silva e , Fatima Carneiro e,f,g , Gintaras Valusis b , Pedro L. Granja a,h,i a INEB – Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal b Terahertz Photonics Laboratory, Optoelectronics Department of the Center for Physical Sciences and Technology, Vilnius, Lithuania c TERAVIL Ltd, Vilnius, Lithuania d Center for Physical Sciences and Technology, Vilnius, Lithuania e FMUP – Faculdade de Medicina, Universidade do Porto, Porto, Portugal f IPATIMUP – Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal g Centro Hospitalar São João, Porto, Portugal h ICBAS – Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal i FEUP – Faculdade de Engenharia, Universidade do Porto, Porto, Portugal highlights  Colon cancer detection by THz-TDS.  Paraffin-embedded samples.  Sample cancer affected tissue zones, low transmittance.  High absorption coefficient and refractive index for affected tissue.  Dehydration of bio-tissues lead t low contrast. article info Article history: Received 21 May 2014 Received in revised form 9 September 2014 Accepted 9 September 2014 Available online 28 September 2014 Keywords: Colon adenocarcinoma Paraffin-embedded samples Pathologic staging Time-domain terahertz spectroscopy Tumor microenvironment abstract In this work, samples of non-neoplastic and adenocarcinoma-affected human colon tissue samples were analyzed using multipoint transmission time-domain THz spectroscopy (THz-TDS) to sort out the contrast-contributing factors other than water, the main contrast mechanism factor in in-vivo or in freshly excised bio-tissue. Solving the electromagnetic inverse problem through THz-TDS and, analyzing the transmittance spectra that yielded the frequency-dependent absorption coefficient a and refractive index n of non-neoplastic and neoplastic tissues, we show that it is possible to distinguish between non-neoplastic and neoplastic regions in paraffin-embedded dehydrated. Results and discussion are presented. Ó 2014 Elsevier B.V. All rights reserved. Introduction Colon cancers is among the most commonly diagnosed cancers and mortality cause (1.23 million, 9.7%) worldwide according to estimates [1]. Early clinical diagnosis is crucial for in time patients’ treatment. Colon cancer is neither rare anywhere in the world, nor mainly confined to high-resource countries. Terahertz time domain spectroscopy (THz-TDS) has had a break- through in the middle of 80’s, and followed by a THz imaging with THz-TDS. Presently, several THz-TDS systems are commercially available, some of them being directly derived from laboratory set- ups while others are compact and integrated with more sophisti- cated man–machine interfaces. The main advantage of a THz-TDS resides on the determination of the broadband response of a sample at once in combination with the actual high stability of the mode- locked lasers, which leads to a very good signal-to-noise ratio (SNR). Moreover, the SNR is reinforced by the time-windowing approach that eliminates a large part of the noise, and the coherent http://dx.doi.org/10.1016/j.molstruc.2014.09.024 0022-2860/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: INEB – Instituto de Engenharia Biomédica, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal. E-mail address: faustino.wahaia@ineb.up.pt (F. Wahaia). Journal of Molecular Structure 1079 (2015) 448–453 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc