Time-Domain Optical Coherence Tomography System for Determining The Extinction Coefficient and Group Refractive Index of Gelatin-based Skin Phantoms

Maria Cecilia Galvez, Edgar Vallar, Tatsuo Shiina, Ernest Macalalad, Paulito Mandia


Optical Coherence Tomography (OCT) is a non-invasive, non-destructive optical imaging technique that uses a low coherence interferometer to obtain real-time cross-sectional images of samples. OCT is notably used in biomedical applications including ophthalmology and dermatology. Aside from generating cross-sectional images, axial scans can also provide additional information about its optical properties such as extinction coefficient and refractive index. This study determines the extinction coefficients and group refractive indices of gelatin-based skin phantoms using a portable time-domain (TD) – OCT system. The gelatin-based skin phantoms were fabricated with varying concentrations of titanium dioxide (TiO2), while keeping the amount of both gelatin and water constant. By changing the proportion of the gelatin powder and TiO2, skin phantoms can then be fabricated to mimic various skin conditions, both pathologic and non-pathologic. Results of the study found a positive correlation of extinction coefficient and refractive index with TiO2 concentration. Thus, increasing TiO2 concentration also increases both extinction coefficient and group refractive index. The median extinction coefficient values of the phantoms ranged from 4.29 mm−1 to 8.48 mm−1. Literature showed that the epidermis can have extinction coefficients of 1.64-7.3 mm−1. For refractive indices of the fabricated phantoms, values ranged from 1.32 to 1.48, while studies on human participants showed that human skin has refractive index values of 1.34-1.56. Based on these properties, it is feasible to fabricate phantoms simulating the optical properties of human skin.


Fujimoto, J., Drexler, W., 2015. Introduction to OCT. In: Fujimoto, J., Drexler, W. (Eds.). Optical coherence tomography: Technology and applications, 2nd ed. Springer, Cham, pp. 3-64.

Fujimoto, J., Huang, D., Swanson, E., Lin, C., Schuman, J., Stinson, W., Chang, W., Hee, M., Flotte, T., Gregory, K., Puliafito, C., 1991. Optical Coherence Tomography. Science, 254, 1178–1180.

Schneider, S., Kohli, I., Hamzavi, I., Council, L., Rossi, A., Ozog, D., 2019. Emerging imaging technologies in dermatology Part I: Basic principles. Journal of the American Academy of Dermatology, 80(4), pp.1114-1120. DOI: 10.1016/j.jaad.2018.11.042.

Pant, C., Olyaee, M., Rastogi, A., 2017. Advanced imaging and therapeutic endoscopy. Techniques in Gastrointestinal Endoscopy, 19(3), pp. 151-158. DOI: 10.1016/j.tgie.2017.08.003.

Poddar, R., Rateria, A., Mohan, M., Mukhopadhyay, K., 2019. Investigation of Puccinia triticina contagion on wheat leaves using swept source optical coherence tomography. Optik, 178, pp. 932-937. DOI: 10.1016/j.ijleo.2018.10.005.

Marques, M., Green, R., King, R., Clement, S., Hallett, P., Podoleanu, A., 2021. Sub-surface characterisation of latest-generation identification documents using optical coherence tomography. Science and Justice, 61(2), pp. 119-129. DOI: 10.1016/j.scijus.2020.12.001.

Izatt, J., Choma, M., Dhalla, A., 2015. Theory of Optical Coherence Tomography. In: Fujimoto J., Drexler, W. (Eds.). Optical coherence tomography: Technology and applications, 2nd ed. Springer, Cham, pp. 65-67.

Liu, P., 2014. Optical Coherence Tomography for Material Characterization. M.S. Thesis. Nanjing University of Aeronautics and Astronautics.

Gambichler, T., Matip, R., Moussa, G., Altmeyer, P., Hoffman, K., 2006. In vivo data of epidermal thickness evaluated by optical coherence tomography: Effects of age, gender, skin type, and anatomic site. Journal of Dermatological Science, 44(3), pp. 145-152. DOI: 10.1016/j.jdermsci.2006.09.008.

James, W., Elston, D., Treat, J., Rosenbach, M., Neuhaus, I., 2020. Andrews’ Diseases of the Skin - Clinical Dermatology. 13th ed. Elsevier, Edinburgh, pp. 14-16.

Emelianov, S., Cook, J., Bouchard, R., 2011. Tissue-mimicking phantoms for photoacoustic and ultrasonic imaging. Biomedical Optics Express, 2(11). pp. 3193-3206. DOI: 10.1364/boe.2.003193.

Kim, Y., 2016. Ultrasound Phantoms to Protect Patients from Novices. Korean Journal of Pain, 29(2). pp. 73-77. DOI: 10.3344/kjp.2016.29.2.73.

Shiina, T., Moritani, Y., Ito, M., Okamura, Y., 2003. Long-optical-path scanning mechanism for optical coherence tomography. Applied Optics, pp. 3795-3799. DOI: 10.1364/ao.42.003795.

Chang, S., Bowden, A., 2019. Review of methods and applications of attenuation coefficient measurements with optical coherence tomography. Journal of Biomedical Optics, 24(9). DOI: 10.1117/1.jbo.24.9.090901.

Adili, D., Shiina, T., 2018. A quantitative evaluation of skin phantom by skin TD-OCT. Proceedings of the 19th Coherent Laser Radar Conference, Okinawa, Japan. pp. 19–22.

Faber, D., van der Meer, F., Aalders, M., van Leeuwen, T., 2004. Quantitative measurement of attenuation coefficients of weakly scattering media using optical coherence tomography. Optics Express, 12(19). pp. 4353-4365. DOI: 10.1364/opex.12.004353.

Cheong, W., Prahl, S., Welch, A., 1990. A Review of the optical properties of biological tissues. IEEE Journal of Quantum Electronics, 26(12). pp. 2166-2185. DOI: 10.1109/3.64354.

Ugryumova, N., Matcher, S., Attenburrow, D., 2004. Measurement of bone mineral density via light scattering. Physics in Medicine and Biology, 49(3). pp. 469-483. DOI: 10.1088/0031-9155/49/3/009.

Tuchin, V., Bashkatov, A., Genina, E., Kochubey, V., Lychagov, V., Portnov, S., Trunina, N., Miller, D., Cho, S., Oh, H., Shim, B., Kim, M., Oh, J., Eum, H., Ku, Y., Kim, D. Yang, Y., 2011.
Finger tissue model and blood perfused skin tissue phantom. Proceedings of SPIE 7898, Dynamics and Fluctuations in Biomedical Photonics VIII, San Francisco, California, USA. pp. 1–11.

E Hecht., 2017. Optics. 5th ed. Pearson Education Limited, England, pp. 76, 103-104, 306.

Yang, Z., Shang, J., Liu, C., Zhang, J., Liang, Y., 2020. Identification of oral cancer in OCT images based on an optical attenuation model. Lasers in Medical Science, 35(9). pp. 1999-2007. DOI: 10.1007/s10103-020-03025-y.

Ahmad, I., Khan, R., Gul, B., Khan, S., Nisar, H., 2021. Refractive index of biological tissues: Review, measurement techniques, and applications. Photodiagnosis and Photodynamic Therapy, 33. pp. 1-9. DOI: 10.1016/j.pdpdt.2021.102192.

Gelatin Manufacturers Institute of America Handbook 2019, Available at: http://www.gelatin-gmia.com/uploads/1/1/8/4/118450438/gmia_gelatin_manual_2019.pdf, accessed June 2021.

Maruyama, H., Inoue, S., Mitsuyama, T., Ohmi, M., Haruna, M., 2002. Low-coherence interferometer system for the simultaneous measurement of refractive index and thickness. Applied Optics, 41(7). pp. 1315-2002. DOI: 10.1364/ao.41.001315.

Tsai, M., Lee, C., Chang, F., Yang, C., Shen, S., Yuan, O., Yang, C., 2013. Evaluation of moisture-related attenuation coefficient and water diffusion velocity in human skin using optical coherence tomography. Sensors, 13(4). pp. 4041-4050. DOI: 10.3390/s130404041.

Psomadakis, C., Marghoob, N., Bleicher, B., Markowitz, O., 2021. Optical coherence tomography. Clinics in Dermatology (In press). DOI: 10.1016/j.clindermatol.2021.03.008


Maria Cecilia Galvez
maria.cecilia.galvez@dlsu.edu.ph (Primary Contact)
Edgar Vallar
Tatsuo Shiina
Ernest Macalalad
Paulito Mandia
Author Biographies

Maria Cecilia Galvez, Environment and Remote Sensing Research Laboratory, Physics Department, De La Salle University, Manila, 2401, Philippines

Full Professor

Vice Chair, Physics Department

College of Science

Tatsuo Shiina, Graduate School of Science and Engineering, Chiba University, Chiba, Japan

 Associate Professor      Graduate School of Engineering Chiba University                                         

Ernest Macalalad, Graduate School of Science and Engineering, Chiba University, Chiba, 271-8510, Japan

Associate Professor

Physics Department, Mapua University

Paulito Mandia, Graduate School of Science and Engineering, Chiba University, Chiba, 271-8510, Japan

Medical Doctor

MS Physics

Assistant Professorial Lecturer, Physics Department

Galvez, M. C., Vallar, E., Shiina, T., Macalalad, E., & Mandia, P. (2021). Time-Domain Optical Coherence Tomography System for Determining The Extinction Coefficient and Group Refractive Index of Gelatin-based Skin Phantoms. Science and Technology Indonesia, 6(4), 319–327. https://doi.org/10.26554/sti.2021.6.4.319-327

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