{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T03:03:19Z","timestamp":1760151799200,"version":"build-2065373602"},"reference-count":23,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2022,4,22]],"date-time":"2022-04-22T00:00:00Z","timestamp":1650585600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100011033","name":"Agencia Estatal de Investigaci\u00f3n","doi-asserted-by":"publisher","award":["PID2019-107885GB-C31\/AEI\/10.13039, PRE2018-084326"],"award-info":[{"award-number":["PID2019-107885GB-C31\/AEI\/10.13039, PRE2018-084326"]}],"id":[{"id":"10.13039\/501100011033","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002341","name":"Academy of Finland","doi-asserted-by":"publisher","award":["327640"],"award-info":[{"award-number":["327640"]}],"id":[{"id":"10.13039\/501100002341","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Improving the longitudinal modes coupling in layered spherical structure contributes significantly to corneal terahertz sensing, which plays a crucial role in the early diagnosis of cornea dystrophies. Using a steel sphere to calibrate reflection from the cornea sample assists in enhancing the resolution of longitudinal modes. The requirement and challenges toward applying the calibration sphere are introduced and addressed. Six corneas with different properties are spotted to study the effect of perturbations in the calibration sphere in a frequency range from 100 GHz to 600 GHz. A particle-swarm optimization algorithm is employed to quantify corneal characteristics considering cases of accurately calibrated and perturbed calibrated scenarios. For the first case, the study is carried out with signal-to-noise values of 40 dB, 50 dB and 60 dB at waveguide bands WR-5.1, WR-3.4, and WR-2.2. As expected, better estimation is achieved in high-SNR cases. Furthermore, the lower waveguide band is revealed as the most proper band for the assessment of corneal features. For perturbed cases, the analysis is continued for the noise level of 60 dB in the three waveguide bands. Consequently, the error in the estimation of corneal properties rises significantly (around 30%).<\/jats:p>","DOI":"10.3390\/s22093237","type":"journal-article","created":{"date-parts":[[2022,4,24]],"date-time":"2022-04-24T00:45:21Z","timestamp":1650761121000},"page":"3237","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Calibration Alignment Sensitivity in Corneal Terahertz Imaging"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1500-2642","authenticated-orcid":false,"given":"Faezeh","family":"Zarrinkhat","sequence":"first","affiliation":[{"name":"CommSensLab, Technical University of Catalonia\/UPC, 08034 Barcelona, Spain"},{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7221-6773","authenticated-orcid":false,"given":"Mariangela","family":"Baggio","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9956-912X","authenticated-orcid":false,"given":"Joel","family":"Lamberg","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2595-5677","authenticated-orcid":false,"given":"Aleksi","family":"Tamminen","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3578-8972","authenticated-orcid":false,"given":"Irina","family":"Nefedova","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2251-5350","authenticated-orcid":false,"given":"Juha","family":"Ala-Laurinaho","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3991-9359","authenticated-orcid":false,"given":"Elsayed E. 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Mag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"e201800145","DOI":"10.1002\/jbio.201800145","article-title":"In vivo estimation of water diffusivity in occluded human skin using terahertz reflection spectroscopy","volume":"12","author":"Sun","year":"2019","journal-title":"J. Biophotonics"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"170","DOI":"10.1109\/TTHZ.2015.2392619","article-title":"THz and mm-wave sensing of corneal tissue water content: Electromagnetic modeling and analysis","volume":"5","author":"Taylor","year":"2015","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"184","DOI":"10.1109\/TTHZ.2015.2392628","article-title":"THz and mm-Wave Sensing of Corneal Tissue Water Content: In Vivo Sensing and Imaging Results","volume":"5","author":"Taylor","year":"2015","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1109\/TTHZ.2017.2775445","article-title":"THz Imaging System for in vivo Human Cornea","volume":"8","author":"Sung","year":"2018","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TTHZ.2017.2771754","article-title":"Optical System Design for Noncontact, Normal Incidence, THz Imaging of in vivo Human Cornea","volume":"8","author":"Sung","year":"2018","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_7","first-page":"963","article-title":"Water gradients across bovine cornea","volume":"29","author":"Castoro","year":"1998","journal-title":"IOVS"},{"key":"ref_8","unstructured":"Orfanidis, S.J. (2002). Electromagnetic Waves and Antennas, Rutgers University New Brunswick."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Zarrinkhat, F., Lamberg, J., Baggio, M., Tamminen, A., Ala-Laurinaho, J., Khaled, E.E.M., Rius, J.M., Robert, J.R., and Taylor, Z. (2021, January 21\u201325). Experimental exploration of longitudinal modes in spherical shells at 220 GHz\u2013330 GHz: Applications to corneal sensing. Proceedings of the CLEO\/Europe-EQEC, Virtual.","DOI":"10.1109\/CLEO\/Europe-EQEC52157.2021.9541679"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1109\/TTHZ.2020.3039454","article-title":"Quasioptical System for Corneal Sensing at 220-330 GHz: Design, Evaluation, and Ex Vivo Cornea Parameter Extraction","volume":"11","author":"Tamminen","year":"2021","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Zarrinkhat, F., Lamberg, J., Tamminen, A., Baggio, M., Ala-Laurinaho, J., Khaled, E.E.M., Rius, J.M., Robert, J.R., and Taylor, Z. (2021, January 22\u201326). Fourier Analysis of Submillimeter-Wave Scattering from the Human Cornea. Proceedings of the 15th European Conference on Antennas and Propagation, D\u00fcsseldorf, Germany.","DOI":"10.23919\/EuCAP51087.2021.9411287"},{"key":"ref_12","unstructured":"Zarrinkhat, F., Lamberg, J., Tamminen, A., Baggio, M., Ala-Laurinaho, J., Khaled, E.E.M., Rius, J., Romeu, J., and Taylor, Z. (2021). Coupling to Longitudinal Modes in Spherical Thin Shells Illuminated by Submillimeter Wave Gaussian Beam: Applications to Corneal Sensing. arXiv."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Baggio, M., Tamminen, A., Presnyakov, S., Kravchenko, N.P., Nefedova, I., Ala-Laurinaho, J., Brown, E., Deng, S., Wallace, V., and Taylor, Z.D. (2021, January 21\u201325). Investigation of optimal THz band for corneal water content quantification. Proceedings of the CLEO\/Europe-EQEC, Virtual.","DOI":"10.1109\/CLEO\/Europe-EQEC52157.2021.9541697"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1109\/TTHZ.2021.3099058","article-title":"Extraction of Thickness and Water-Content Gradients in Hydrogel-Based Water-Backed Corneal Phantoms Via Submillimeter-Wave Reflectometry","volume":"11","author":"Tamminen","year":"2021","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_15","first-page":"295","article-title":"Scattered and internal intensity of a sphere illuminated with a Gaussian beam","volume":"41","author":"Khaled","year":"1993","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"3308","DOI":"10.1364\/AO.33.003308","article-title":"Light scattering by a coated sphere illuminated with a Gaussian beam","volume":"33","author":"Khaled","year":"1994","journal-title":"Appl. Opt."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Barber, P.W., and Hill, S.C. (1990). Light Scattering by Particles: Computational Methods, World Scientific.","DOI":"10.1142\/9789814317689"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Bohren, C., and Huffman, D.R. (1998). Absorption and Scattering of Light by Small Particles, Wiley.","DOI":"10.1002\/9783527618156"},{"key":"ref_19","first-page":"69","article-title":"Scattering of electromagnetic radiation by a multilayered sphere","volume":"57","author":"Pal","year":"2015","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_20","first-page":"031908","article-title":"0.15\u20133.72 THz absorption of aqueous salts and saline solutions","volume":"90","author":"Xu","year":"2007","journal-title":"Appl. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"538","DOI":"10.1109\/TTHZ.2021.3088273","article-title":"Submillimeter-Wave Permittivity Measurements of Bound Water in Collagen Hydrogels via Frequency Domain Spectroscopy","volume":"11","author":"Tamminen","year":"2021","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_22","unstructured":"Hespanha, J.P. (2021, March 26). Topics in Undergraduate Control Systems Design. Available online: https:\/\/web.ece.ucsb.edu\/~hespanha\/published\/allugtopics-20210326.pdf."},{"key":"ref_23","unstructured":"Kennedy, J., and Eberhart, R. (December, January 27). Particle swarm optimization. Proceedings of the ICNN\u201995, Perth, Australia."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3237\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:59:07Z","timestamp":1760137147000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3237"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,4,22]]},"references-count":23,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2022,5]]}},"alternative-id":["s22093237"],"URL":"https:\/\/doi.org\/10.3390\/s22093237","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2022,4,22]]}}}