The optical response of biological matter reflects its complex architecture in a microscopic (50nm-50μm) as well as macroscopic (>mm) scale, encompassing inhomogeneity, absorption and photon multiple scattering effects. Understanding light-tissue interactions emerges as a challenging topic of fundamental research that can have a direct impact on biomedical applications, such as phototherapy, microscopy and optical diagnosis. To analyse the micro-optical properties of tissues, the concept of the “effective” refractive index is commonly used within the frame of an effective medium theory.
This approach treats tissue as an optically turbid medium, whose refractive index equals the sum of its mean (“effective index”) and a relatively small spatially varying part; then, a laser beam propagating through tissue carries a coherent component, which corresponds to the “average” electromagnetic field and decreases with penetration depth, as well as a diffuse component, which corresponds to the local fluctuations of the electromagnetic field around its average. Under these assumptions, the tissue effective refractive index may be perceived as the microscopically-averaged refractive index experienced by the coherent light component.
We investigate the refractive properties of freshly excised, non-fixed human tissues and biofluids. This project has produced encouraging results clearly indicating the potential use of the effective refractive index for marking liver cancer, colorectal dysplasia and breast fibroadenoma. In view of the current progress in optical biosensor technologies, our findings may pave the way for the development of novel surgical and endoscopic tools.
Group’s journal publications on this topic [click for more]
16 M. Matiatou, P. Giannios, S. Koutsoumpos, N.V. Michalopoulos, K.G. Toutouzas, G.C. Zografos, K. Moutzouris. Complex refractive index of freshly excised human breast tissue as a marker of disease. Lasers in Medical Sciences (published online), 1-8 (2022).
13 M. Matiatou, P. Giannios, S. Koutsoumpos, K.G Toutouzas, G.C Zografos, K. Moutzouris. Data on the refractive index of freshly-excised human tissues in the visible and near-infrared spectral range. Results in Physics 22, 103833 (2021).
8 P. Giannios, S. Koutsoumpos, K.G. Toutouzas, M. Matiatou, G.C Zografos, K. Moutzouris. Complex refractive index of normal and malignant human colorectal tissue in the visible and near infrared. Journal of Biophotonics 10, 303 (2017).
7 P. Giannios, K.G Toutouzas, M. Matiatou, K. Stasinos, M.M Konstadoulakis, G.C Zografos, K. Moutzouris. Visible to near infrared refractive properties of freshly-excised human-liver tissues: Marking hepatic malignancies. Scientific Reports 6, 27910 (2016).
Group’s conference publications on this topic [click for more]
9 M. Matiatou, P. Giannios, K. Moutzouris, N. Michalopoulos, S. Koutsoumpos, K. Toutouzas, G.C Zografos. Correlation of tissue optical characteristics to breast pathology. 16th St. Gallen International Breast Cancer Conference ( BCC 2019). 20 – 23 March 2019. Vienna, Austria. The Breast 44, S131 (2019).
8 M. Matiatou, P. Giannios, K. Moutzouris, N. Michalopoulos, S. Koutsoumpos, K. Toutouzas, G.C Zografos. Identifying a relation between refractive index and breast pathology using prism coupling refractometry. 11th European Breast Cancer Congress (EBCC11). 21 – 23 March 2018. Barcelona, Spain. European Journal of Cancer 92, S126 (2018).
6 P. Giannios, K.G Toutouzas, M. Matiatou, K. Stasinos, M.M Konstadoulakis, G.C Zografos, K. Moutzouris. Visible to near infrared refractive properties of freshly-excised human-liver tissues: Marking hepatic malignancies. 30th Panhellenic Congress of Surgery & International Surgical Forum “Quality & Security in Surgery”. 9 – 12 November 2016. Thessaloniki, Greece.
5 K. Toutouzas, K. Moutzouris, M. Matiatou, G.C Zografos, P. Giannios. Refractive index as a potential marker for hepatic malignancies. 27th International Conference of the Society for Medical Innovation and Technology. 10 – 12 September 2015. Brno, Czech Republic.
4 P. Giannios, K. Moutzouris, M. Matiatou, G. Georgiou, G.C Zografos, K. Toutouzas. Refractive index as a novel tumor marker. 29th Panhellenic Congress of Surgery & International Surgical Forum. 12 – 15 November 2014. Athens, Greece.