Prof. Ilias Tachtsidis Profile

Prof. Ilias Tachtsidis

Professor at Univ College London

SPIE Involvement:

Author

Publications (46)

SPIE Journal Paper | 2 December 2024 Open Access

Digital instrument simulator to optimize the development of hyperspectral systems: application for intraoperative functional brain mapping

Charly Caredda, Frédéric Lange, Luca Giannoni, Ivan Ezhov, Thiébaud Picart, Jacques Guyotat, Ilias Tachtsidis, Bruno Montcel

JBO, Vol. 30, Issue 02, 023513, (December 2024) https://doi.org/10.1117/12.10.1117/1.JBO.30.2.023513

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SignificanceIntraoperative optical imaging is a localization technique for the functional areas of the human brain cortex during neurosurgical procedures. These areas can be assessed by monitoring cerebral hemodynamics and metabolism. Robust quantification of these biomarkers is complicated to perform during neurosurgery due to the critical context of the operating room. In actual devices, the inhomogeneities of the optical properties of the exposed brain cortex are poorly taken into consideration, which introduce quantification errors of biomarkers of brain functionality. Moreover, the best choice of spectral configuration is still based on an empirical approach.AimWe propose a digital instrument simulator to optimize the development of hyperspectral systems for intraoperative brain mapping studies. This simulator can provide realistic modeling of the cerebral cortex and the identification of the optimal wavelengths to monitor cerebral hemodynamics (oxygenated HbO2 and deoxygenated hemoglobin Hb) and metabolism (oxidized state of cytochromes b and c and cytochrome-c-oxidase oxCytb, oxCytc, and oxCCO).ApproachThe digital instrument simulator is computed with white Monte Carlo simulations of a volume created from a real image of exposed cortex. We developed an optimization procedure based on a genetic algorithm to identify the best wavelength combinations in the visible and near-infrared range to quantify concentration changes in HbO2, Hb, oxCCO, and the oxidized state of cytochrome b and c (oxCytb and oxCytc).ResultsThe digital instrument allows the modeling of intensity maps collected by a camera sensor as well as images of path length to take into account the inhomogeneities of the optical properties. The optimization procedure helps to identify the best wavelength combination of 18 wavelengths that reduces the quantification errors in HbO2, Hb, and oxCCO by 47%, 57%, and 57%, respectively, compared with the gold standard of 121 wavelengths between 780 and 900 nm. The optimization procedure does not help to resolve changes in cytochrome b and c in a significant way but helps to better resolve oxCCO changes.ConclusionsWe proposed a digital instrument simulator to optimize the development of hyperspectral systems for intraoperative brain mapping studies. This digital instrument simulator and this optimization framework could be used to optimize the design of hyperspectral imaging devices.

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SPIE Journal Paper | 24 September 2024 Open Access

Learnable real-time inference of molecular composition from diffuse spectroscopy of brain tissue

Ivan Ezhov, Kevin Scibilia, Luca Giannoni, Florian Kofler, Ivan Iliash, Felix Hsieh, Suprosanna Shit, Charly Caredda, Frédéric Lange, Bruno Montcel, Ilias Tachtsidis, Daniel Rueckert

JBO, Vol. 29, Issue 09, 093509, (September 2024) https://doi.org/10.1117/12.10.1117/1.JBO.29.9.093509

KEYWORDS: Scattering, Data modeling, Machine learning, Education and training, Body composition, RGB color model, Near infrared spectroscopy, Brain tissue, Tissues, Absorption

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SPIE Journal Paper | 10 September 2024 Open Access

Transportable hyperspectral imaging setup based on fast, high-density spectral scanning for in situ quantitative biochemical mapping of fresh tissue biopsies

Luca Giannoni, Marta Marradi, Kevin Scibilia, Ivan Ezhov, Camilla Bonaudo, Angelos Artemiou, Anam Toaha, Frédéric Lange, Charly Caredda, Bruno Montcel, Alessandro Della Puppa, Ilias Tachtsidis, Daniel Rückert, Francesco Saverio Pavone

JBO, Vol. 29, Issue 09, 093508, (September 2024) https://doi.org/10.1117/12.10.1117/1.JBO.29.9.093508

KEYWORDS: Biopsy, Biological samples, Tissues, Near infrared, Visible radiation, Hyperspectral imaging, 3D modeling, Reflectivity, Statistical analysis, Tumors

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SignificanceHistopathological examination of surgical biopsies, such as in glioma and glioblastoma resection, is hindered in current clinical practice by the long time required for the laboratory analysis and pathological screening, typically taking several days or even weeks to be completed.AimWe propose here a transportable, high-density, spectral scanning-based hyperspectral imaging (HSI) setup, named HyperProbe1, that can provide in situ, fast biochemical analysis, and mapping of fresh surgical tissue samples, right after excision, and without the need for fixing, staining nor compromising the integrity of the tissue properties.ApproachHyperProbe1 is based on spectral scanning via supercontinuum laser illumination filtered with acousto-optic tunable filters. Such methodology allows the user to select any number and type of wavelength bands in the visible and near-infrared range between 510 and 900 nm (up to a maximum of 79) and to reconstruct 3D hypercubes composed of high-resolution (4 to 5 μm), widefield images (0.9×0.9 mm2) of the surgical samples, where each pixel is associated with a complete spectrum.ResultsThe HyperProbe1 setup is here presented and characterized. The system is applied to 11 fresh surgical biopsies of glioma from routine patients, including different grades of tumor classification. Quantitative analysis of the composition of the tissue is performed via fast spectral unmixing to reconstruct the mapping of major biomarkers, such as oxy-(HbO2) and deoxyhemoglobin (HHb), as well as cytochrome-c-oxidase (CCO). We also provided a preliminary attempt to infer tumor classification based on differences in composition in the samples, suggesting the possibility of using lipid content and differential CCO concentrations to distinguish between lower and higher-grade gliomas.ConclusionsA proof of concept of the performances of HyperProbe1 for quantitative, biochemical mapping of surgical biopsies is demonstrated, paving the way for improving current post-surgical, histopathological practice via non-destructive, in situ streamlined screening of fresh tissue samples in a matter of minutes after excision.

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Proceedings Article | 18 June 2024 Poster + Paper

Pixel-wise and real-time estimation of optical mean path length using deep learning: application for intraoperative functional brain mapping

Charly Caredda, Ivan Ezhov, Michaël Sdika, Frederic Lange, Luca Giannoni, Ilias Tachtsidis, Bruno Montcel

Proceedings Volume 13009, 130090F (2024) https://doi.org/10.1117/12.3016632

KEYWORDS: Brain, Image segmentation, Monte Carlo methods, Brain mapping, Deep learning, Neural networks, Tissue optics, RGB color model, Optical imaging

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Proceedings Article | 18 June 2024 Presentation + Paper

A digital instrument simulator to optimize the development of hyperspectral systems for intraoperative brain mapping

Charly Caredda, Frederic Lange, Luca Giannoni, Ivan Ezhov, Ilias Tachtsidis, Bruno Montcel

Proceedings Volume 13010, 130100L (2024) https://doi.org/10.1117/12.3017488

KEYWORDS: Monte Carlo methods, RGB color model, Device simulation, Hemodynamics, Hyperspectral simulation, Brain mapping, Hyperspectral systems, Brain, Neurosurgery

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Proceedings Article | 21 August 2023 Paper

Evaluation of hyperspectral imaging measurements of changes in hemoglobin oxygenation and oxidation of cytochrome-c-oxidase using a liquid blood phantom

Charly Caredda, Frédéric Lange, Ilias Tachtsidis, Bruno Montcel

Proceedings Volume 12628, 126280Q (2023) https://doi.org/10.1117/12.2670746

KEYWORDS: Liquids, Hyperspectral imaging, Blood, Yeast, Oxygenation, Oxidation, Oxygen, Hemodynamics, Standards development, Reliability

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Proceedings Article | 9 August 2023 Paper

A digital instrument simulator to optimize the development of a hyperspectral imaging system for neurosurgery

Frédéric Lange, Luca Giannoni, Fernand Fort, Charly Caredda, Bruno Montcel, Ilias Tachtsidis

Proceedings Volume 12628, 126282C (2023) https://doi.org/10.1117/12.2670873

KEYWORDS: Equipment, Neurosurgery, Monte Carlo methods, Imaging systems, Hyperspectral imaging, Device simulation, Hyperspectral simulation, Simulations, Nervous system, Algorithm development

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Proceedings Article | 9 August 2023 Paper

HyperProbe consortium: innovate tumour neurosurgery with innovative photonic solutions

Luca Giannoni, Marta Marradi, Marco Marchetti, Duccio Rossi Degl'Innocenti, Ivan Ezhov, Charly Caredda, Arthur Gautheron, Fernand Fort, Fabien Schneider, Moncef Berhouma, Camilla Bonaudo, Thiébaud Picart, Frédéric Lange, Katharina Krischak, Peter Gordebeke, Domenico Alfieri, Daniel Rückert, Bruno Montcel, Alessandro Della Puppa, Jacques Guyotat, Ilias Tachtsidis, Francesco Pavone

Proceedings Volume 12628, 126281C (2023) https://doi.org/10.1117/12.2670764

KEYWORDS: Neurosurgery, Brain, Surgery, Neuroimaging, Image restoration, Image analysis, Artificial intelligence, Positron emission tomography, Physiology, Optical phantoms

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Proceedings Article | 9 August 2023 Paper

Identifying chromophore fingerprints of brain tumor tissue on hyperspectral imaging using principal component analysis

Ivan Ezhov, Luca Giannoni, Suprosanna Shit, Frédéric Lange, Florian Kofler, Bjoern Menze, Ilias Tachtsidis, Daniel Rueckert

Proceedings Volume 12628, 1262826 (2023) https://doi.org/10.1117/12.2670775

KEYWORDS: Tissues, Tumors, Chromophores, Blood vessels, Principal component analysis, Absorption, Absorption spectrum, Reflectivity, Brain tissue, Statistical analysis

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Proceedings Article | 9 August 2023 Paper

Classification of brain injury severity using a hybrid broadband NIRS and DCS instrument with a machine learning approach

Danai Bili, Frédéric Lange, Kelly Harvey Jones, Veronika Parfentyeva, Turgut Durduran, Nikki Robertson, Subhabrata Mitra, Ilias Tachtsidis

Proceedings Volume 12628, 126280D (2023) https://doi.org/10.1117/12.2670657

KEYWORDS: Machine learning, Feature extraction, Traumatic brain injury, Near infrared spectroscopy, Injuries, Equipment, Brain, Spectroscopy

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Proceedings Article | 9 August 2023 Paper

Testing novel miniature NIR spectrometers for wearable broadband NIRS devices

M. Talati, F. Lange, I. Tachtsidis

Proceedings Volume 12628, 126282B (2023) https://doi.org/10.1117/12.2668162

KEYWORDS: Signal to noise ratio, Spectrometers, Near infrared, Light sources, Lamps, Interference (communication), Spectral response, Portability, Tissues, Source detector separation, Near infrared spectroscopy, Functional near infrared spectroscopy

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SPIE Journal Paper | 23 March 2023 Open Access

Taking the lid off ambitions for optical imaging of the human brain: a conversation with Clare Elwell

Ilias Tachtsidis

NPh, Vol. 10, Issue 02, 020401, (March 2023) https://doi.org/10.1117/12.10.1117/1.NPh.10.2.020401

KEYWORDS: Optical imaging, Neuroimaging, Brain, Brain imaging, Spectroscopy, Medical research, Medical physics, Imaging spectroscopy, Head, Engineering

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SPIE Journal Paper | 30 August 2022 Open Access

Optical imaging and spectroscopy for the study of the human brain: status report

Hasan Ayaz, Wesley Baker, Giles Blaney, David Boas, Heather Bortfeld, Kenneth Brady, Joshua Brake, Sabrina Brigadoi, Erin M. Buckley, Stefan Carp, Robert Cooper, Kyle Cowdrick, Joseph Culver, Ippeita Dan, Hamid Dehghani, Anna Devor, Turgut Durduran, Adam Eggebrecht, Lauren Emberson, Qianqian Fang, Sergio Fantini, Maria Angela Franceschini, Jonas Fischer, Judit Gervain, Joy Hirsch, Keum-Shik Hong, Roarke Horstmeyer, Jana Kainerstorfer, Tiffany Ko, Daniel Licht, Adam Liebert, Robert Luke, Jennifer Lynch, Jaume Mesquida, Rickson Mesquita, Noman Naseer, Sergio Novi, Felipe Orihuela-Espina, Thomas O'Sullivan, Darcy Peterka, Antonio Pifferi, Luca Pollonini, Angelo Sassaroli, João Ricardo Sato, Felix Scholkmann, Lorenzo Spinelli, Vivek Srinivasan, Keith St. Lawrence, Ilias Tachtsidis, Yunjie Tong, Alessandro Torricelli, Tara Urner, Heidrun Wabnitz, Martin Wolf, Ursula Wolf, Shiqi Xu, Changhuei Yang, Arjun Yodh, Meryem Yücel, Wenjun Zhou

NPh, Vol. 9, Issue S2, S24001, (August 2022) https://doi.org/10.1117/12.10.1117/1.NPh.9.S2.S24001

KEYWORDS: Brain, Near infrared spectroscopy, Neuroimaging, Imaging spectroscopy, Sensors, Optical imaging, Optical spectroscopy imaging, Optical spectroscopy, Spectroscopy, Tissue optics

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SPIE Journal Paper | 11 July 2022 Open Access

Systemic physiology augmented functional near-infrared spectroscopy: a powerful approach to study the embodied human brain

Felix Scholkmann, Ilias Tachtsidis, Martin Wolf, Ursula Wolf

NPh, Vol. 9, Issue 03, 030801, (July 2022) https://doi.org/10.1117/12.10.1117/1.NPh.9.3.030801

KEYWORDS: Physiology, Brain, Hemodynamics, Near infrared spectroscopy, Neuroimaging, Functional magnetic resonance imaging, Neurophotonics, Head, Visualization, Signal processing

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SPIE Journal Paper | 15 June 2022 Open Access

Multi-laboratory performance assessment of diffuse optics instruments: the BitMap exercise

Pranav Lanka, Lin Yang, David Orive-Miguel, Joshua Deepak Veesa, Susanna Tagliabue, Aleh Sudakou, Saeed Samaei, Mario Forcione, Zuzana Kovacsova, Anurag Behera, Thomas Gladytz, Dirk Grosenick, Lionel Hervé, Turgut Durduran, Karolina Bejm, Magdalena Morawiec, Michał Kacprzak, Piotr Sawosz, Anna Gerega, Adam Liebert, Antonio Belli, Ilias Tachtsidis, Frédéric Lange, Gemma Bale, Luca Baratelli, Sylvain Gioux, Alexander Kalyanov, Martin Wolf, Sanathana Konugolu-Venkata-Sekar, Marta Zanoletti, Ileana Pirovano, Michele Lacerenza, Lina Qiu, Edoardo Ferocino, Giulia Maffeis, Caterina Amendola, Lorenzo Colombo, Lorenzo Frabasile, Pietro Levoni, Mauro Buttafava, Marco Renna, Laura Di Sieno, Rebecca Re, Andrea Farina, Lorenzo Spinelli, Alberto Dalla Mora, Davide Contini, Paola Taroni, Alberto Tosi, Alessandro Torricelli, Hamid Dehghani, Heidrun Wabnitz, Antonio Pifferi

JBO, Vol. 27, Issue 07, 074716, (June 2022) https://doi.org/10.1117/12.10.1117/1.JBO.27.7.074716

KEYWORDS: Raster graphics, Optical properties, Diffuse optical imaging, Scattering, Imaging spectroscopy, Absorption, Tissue optics, Spectroscopes, Sensors, Oximetry

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SPIE Journal Paper | 18 May 2022 Open Access

Investigation of functional near-infrared spectroscopy signal quality and development of the hemodynamic phase correlation signal

Uzair Hakim, Paola Pinti, J. Adam Noah, Xian Zhang, Paul Burgess, Antonia Hamilton, Joy Hirsch, Ilias Tachtsidis

NPh, Vol. 9, Issue 02, 025001, (May 2022) https://doi.org/10.1117/12.10.1117/1.NPh.9.2.025001

KEYWORDS: Signal to noise ratio, Hemodynamics, Near infrared spectroscopy, Brain, Neurophotonics, Data acquisition, Signal analyzers, Chromophores, Brain activation, Data modeling

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Significance: There is a longstanding recommendation within the field of fNIRS to use oxygenated (HbO2) and deoxygenated (HHb) hemoglobin when analyzing and interpreting results. Despite this, many fNIRS studies do focus on HbO2 only. Previous work has shown that HbO2 on its own is susceptible to systemic interference and results may mostly reflect that rather than functional activation. Studies using both HbO2 and HHb to draw their conclusions do so with varying methods and can lead to discrepancies between studies. The combination of HbO2 and HHb has been recommended as a method to utilize both signals in analysis. Aim: We present the development of the hemodynamic phase correlation (HPC) signal to combine HbO2 and HHb as recommended to utilize both signals in the analysis. We use synthetic and experimental data to evaluate how the HPC and current signals used for fNIRS analysis compare. Approach: About 18 synthetic datasets were formed using resting-state fNIRS data acquired from 16 channels over the frontal lobe. To simulate fNIRS data for a block-design task, we superimposed a synthetic task-related hemodynamic response to the resting state data. This data was used to develop an HPC-general linear model (GLM) framework. Experiments were conducted to investigate the performance of each signal at different SNR and to investigate the effect of false positives on the data. Performance was based on each signal’s mean T-value across channels. Experimental data recorded from 128 participants across 134 channels during a finger-tapping task were used to investigate the performance of multiple signals [HbO2, HHb, HbT, HbD, correlation-based signal improvement (CBSI), and HPC] on real data. Signal performance was evaluated on its ability to localize activation to a specific region of interest. Results: Results from varying the SNR show that the HPC signal has the highest performance for high SNRs. The CBSI performed the best for medium-low SNR. The next analysis evaluated how false positives affect the signals. The analyses evaluating the effect of false positives showed that the HPC and CBSI signals reflect the effect of false positives on HbO2 and HHb. The analysis of real experimental data revealed that the HPC and HHb signals provide localization to the primary motor cortex with the highest accuracy. Conclusions: We developed a new hemodynamic signal (HPC) with the potential to overcome the current limitations of using HbO2 and HHb separately. Our results suggest that the HPC signal provides comparable accuracy to HHb to localize functional activation while at the same time being more robust against false positives.

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Proceedings Article | 9 December 2021 Paper

Cerebral time domain near-infrared spectroscopy of people with multiple sclerosis: a feasibility study

Frédéric Lange, T. Williams, J. Chataway, K. Smith, I. Tachtsidis

Proceedings Volume 11920, 119200S (2021) https://doi.org/10.1117/12.2615251

KEYWORDS: Brain, Near infrared spectroscopy, Hemodynamics, Control systems, Tissue optics, Absorption, Tissues, Optical properties, Data processing, Clinical trials

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Proceedings Article | 9 December 2021 Paper

Does wearing a non-medical face mask cause changes in cerebral hemodynamics?

Jonas Fischer, Lisa Kobayashi Frisk, Ilias Tachtsidis, Raquel Delgado Mederos, Mercedes Mayos Pèrez, Felix Scholkmann, Turgut Durduran

Proceedings Volume 11920, 119200J (2021) https://doi.org/10.1117/12.2615227

KEYWORDS: Hemodynamics, Cognitive informatics, Transparent conductors, Physiology, Neuroimaging, Data acquisition, Time resolved spectroscopy, Spectroscopy, Neuroscience, Medical research

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Proceedings Article | 9 December 2021 Paper

An optical biomarker of hypoxic-ischaemic injury severity in the neonatal brain

Ilias Tachtsidis, Frédéric Lange, Paola Pinti, Gemma Bale, Magdalena Sokolska, Adnan Avdic-Belltheus, Christopher Meehan, Nicola Robertson, Shahrzad Parsa, Udo Weigel, Turgut Durduran, Subhrabrata Mitra

Proceedings Volume 11920, 119200I (2021) https://doi.org/10.1117/12.2615226

KEYWORDS: Brain, Injuries, Mode conditioning cables, Spectroscopy, Near infrared spectroscopy, Blood, Traumatic brain injury, Cerebral blood flow, Visualization, Therapeutics

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Proceedings Article | 5 March 2021 Presentation + Paper

A multi-laboratory comparison of photon migration instruments and their performances: the BitMap exercise

Sri Rama Pranav Kumar Lanka, Lin Yang, David Orive-Miguel, Joshua Deepak Veesa, Susanna Tagliabue, Aleh Sudakou, Saeed Samaei, Mario Forcione, Zuzana Kovacsova, Anurag Behera, Thomas Gladytz, Dirk Grosenick, Lionel Hervé, Giuseppe Lo Presti, Lorenzo Cortese, Turgut Durduran, Karolina Bejm, Magdalena Morawiec, Piotr Sawosz, Michal Kacprzak, Anna Gerega, Adam Liebert, Antonio Belli, Ilias Tachtsidis, Frédéric Lange, Gemma Bale, Luca Baratelli, Sylvain Gioux, Alexander Kalyanov, Martin Wolf, Sanathana Konugolu Venkata Sekar, Marta Zanoletti, Ileana Pirovano, Michele Lacerenza, Lina Qiu, Edoardo Ferocino, Giulia Maffeis, Caterina Amendola, Lorenzo Colombo, Mauro Buttafava, Marco Renna, Laura Di Sieno, Rebecca Re, Andrea Farina, Lorenzo Spinelli, Alberto Dalla Mora, Davide Contini, Alessandro Torricelli, Alberto Tosi, Paola Taroni, Hamid Dehghani, Heidrun Wabnitz, Antonio Pifferi

Proceedings Volume 11639, 116390F (2021) https://doi.org/10.1117/12.2578521

KEYWORDS: Raster graphics, Photonic devices, Tissue optics, Spectroscopes, Oximetry, Optical components, Mammography, Imaging spectroscopy, Functional imaging

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SPIE Journal Paper | 13 February 2021 Open Access

Comparison of short-channel separation and spatial domain filtering for removal of non-neural components in functional near-infrared spectroscopy signals

J. Adam Noah, Xian Zhang, Swethasri Dravida, Courtney DiCocco, Tatsuya Suzuki, Richard Aslin, Ilias Tachtsidis, Joy Hirsch

NPh, Vol. 8, Issue 01, 015004, (February 2021) https://doi.org/10.1117/12.10.1117/1.NPh.8.1.015004

KEYWORDS: Spatial filters, Hemodynamics, Electronic filtering, Visualization, Head, Neurophotonics, Sensors, Filtering (signal processing), Data modeling, Functional magnetic resonance imaging

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SPIE Journal Paper | 8 February 2021 Open Access

Errata: Best practices for fNIRS publications

Meryem Yücel, Alexander von Lühmann, Felix Scholkmann, Judit Gervain, Ippeita Dan, Hasan Ayaz, David Boas, Robert J. Cooper, Joseph Culver, Clare Elwell, Adam Eggebrecht, Maria Angela Franceschini, Christophe Grova, Fumitaka Homae, Frédéric Lesage, Hellmuth Obrig, Ilias Tachtsidis, Sungho Tak, Yunjie Tong, Alessandro Torricelli, Heidrun Wabnitz, Martin Wolf

NPh, Vol. 8, Issue 01, 019802, (February 2021) https://doi.org/10.1117/12.10.1117/1.NPh.8.1.019802

KEYWORDS: Biomedical engineering, Medical research, Neurophotonics, Analytical research, Radiology, Medicine, Biomedical optics, Psychology, Medical physics, Functional imaging

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SPIE Journal Paper | 7 January 2021 Open Access

Best practices for fNIRS publications

Meryem Yücel, Alexander Lühmann, Felix Scholkmann, Judit Gervain, Ippeita Dan, Hasan Ayaz, David Boas, Robert Cooper, Joseph Culver, Clare Elwell, Adam Eggebrecht, Maria Franceschini, Christophe Grova, Fumitaka Homae, Frédéric Lesage, Hellmuth Obrig, Ilias Tachtsidis, Sungho Tak, Yunjie Tong, Alessandro Torricelli, Heidrun Wabnitz, Martin Wolf

NPh, Vol. 8, Issue 01, 012101, (January 2021) https://doi.org/10.1117/12.10.1117/1.NPh.8.1.012101

KEYWORDS: Statistical analysis, Brain, Signal processing, Neurophotonics, Sensors, Hemodynamics, Tissues, Standards development, Head, Visualization

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SPIE Journal Paper | 27 November 2020 Open Access

Interpolated functional manifold for functional near-infrared spectroscopy analysis at group level

Shender-María Ávila-Sansores, Gustavo Rodríguez-Gómez, Ilias Tachtsidis, Felipe Orihuela-Espina

NPh, Vol. 7, Issue 04, 045009, (November 2020) https://doi.org/10.1117/12.10.1117/1.NPh.7.4.045009

KEYWORDS: Brain, Near infrared spectroscopy, Hemodynamics, Error analysis, Neurophotonics, Clouds, Statistical analysis, Analytical research, Visualization, Neuroimaging

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Proceedings Article | 4 October 2020 Presentation

Early bedside broadband near-infrared spectroscopy (bNIRS) markers of neonatal brain injury: quantifying oxygenation and in-vivo mitochondrial function

Ilias Tachtsidis

Proceedings Volume 11575, 1157508 (2020) https://doi.org/10.1117/12.2584758

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SPIE Journal Paper | 1 April 2020 Open Access

Investigation of the quantification of hemoglobin and cytochrome-c-oxidase in the exposed cortex with near-infrared hyperspectral imaging: a simulation study

Luca Giannoni, Frédéric Lange, Ilias Tachtsidis

JBO, Vol. 25, Issue 04, 046001, (April 2020) https://doi.org/10.1117/12.10.1117/1.JBO.25.4.046001

KEYWORDS: Hemodynamics, Monte Carlo methods, Near infrared, Brain, Hyperspectral simulation, Hypoxia, Photodetectors, Sensors, Computer simulations, Tissues

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Proceedings Article | 1 April 2020 Presentation

Neuromonitoring with broadband near-infrared spectroscopy brain oxygenation and metabolism: application in newborn brain injury (Conference Presentation)

Ilias Tachtsidis

Proceedings Volume 11362, 113620D (2020) https://doi.org/10.1117/12.2554713

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Near-Infrared Spectroscopy (NIRS) instruments most often measures the reflected NIR attenuation at a couple of wavelengths, to quantify the concentration of the oxygenated and deoxygenated hemoglobin ([HbO2], [HHb]) and provide information about the brain oxygen levels. Of particular interest are the changes in brain oxygenation due to neuronal activity as they can provide us with an indirect measurement of brain function. For several years now we have been developing technology that extend NIRS instrumentation by allowing measuring hundreds of NIR wavelengths. The technique is called broadband near-infrared spectroscopy (or bNIRS). The bNIRS system measures changes in light attenuation, reflected back from the head, over 308 near-infrared (NIR) wavelengths (610nm-918nm). This allow us to quantify the changes in brain tissue [HbO2], [HHb] and the concentration changes in the oxidation state of cerebral cytochrome-c-oxidase ([oxCCO]). CCO is an enzyme in the electron transport chain of the mitochondrial catalyzing more than 95% of oxygen to produce ATP. In my talk I will discuss how we have been using this technology both in our preclinical and clinical investigations in perinatal hypoxic-ischemia. In particular, I will introduce our clinical study in newborns with Hypoxic-Ischemic (HI) injury undergoing therapeutic hypothermia. In 24 neonates, 54 episodes of spontaneous decreases in peripheral oxygen saturation (desaturations) were recorded between 6h and 81h after birth. As determined by magnetic resonance spectroscopy derived lactate/N-acetyl-aspartate (MRS-measured Lac/NAA) 8 newborns had unfavorable and 16 newborns had favorable outcomes after HI. We demonstrated that a strong relationship between cerebral metabolism (bNIRS-measured oxCCO) and oxygenation was associated with unfavorable outcome; this is likely to be due to a lower cerebral metabolic rate and mitochondrial dysfunction in severe encephalopathy. In addition, uniquely we have obtained these results using a non-invasive bedside technique, bNIRS, in the first 4 days of life.

SPIE Journal Paper | 14 November 2019 Open Access

Quantification of the severity of hypoxic-ischemic brain injury in a neonatal preclinical model using measurements of cytochrome-c-oxidase from a miniature broadband-near-infrared spectroscopy system

Pardis Kaynezhad, Subhabrata Mitra, Gemma Bale, Cornelius Bauer, Ingran Lingam, Christopher Meehan, Adnan Avdic-Belltheus, Kathryn Martinello, Alan Bainbridge, Nicola Robertson, Ilias Tachtsidis

NPh, Vol. 6, Issue 04, 045009, (November 2019) https://doi.org/10.1117/12.10.1117/1.NPh.6.4.045009

KEYWORDS: Spectroscopy, Injuries, Brain, Traumatic brain injury, Signal attenuation, Tissue optics, Chromophores, Charge-coupled devices, Neurophotonics, Mode conditioning cables

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We describe the development of a miniaturized broadband near-infrared spectroscopy system (bNIRS), which measures changes in cerebral tissue oxyhemoglobin ( [ HbO₂ ] ) and deoxyhemoglobin ([HHb]) plus tissue metabolism via changes in the oxidation state of cytochrome-c-oxidase ([oxCCO]). The system is based on a small light source and a customized mini-spectrometer. We assessed the instrument in a preclinical study in 27 newborn piglets undergoing transient cerebral hypoxia-ischemia (HI). We aimed to quantify the recovery of the HI insult and estimate the severity of the injury. The recovery in brain oxygenation (Δ [ HbDiff ] = Δ [ HbO₂ ] − Δ [ HHb ] ), blood volume (Δ [ HbT ] = Δ [ HbO₂ ] + Δ [ HHb ] ), and metabolism (Δ [ oxCCO ] ) for up to 30 min after the end of HI were quantified in percentages using the recovery fraction (RF) algorithm, which quantifies the recovery of a signal with respect to baseline. The receiver operating characteristic analysis was performed on bNIRS-RF measurements compared to proton (H1) magnetic resonance spectroscopic (MRS)-derived thalamic lactate/N-acetylaspartate (Lac/NAA) measured at 24-h post HI insult; Lac/NAA peak area ratio is an accurate surrogate marker of neurodevelopmental outcome in babies with neonatal HI encephalopathy. The Δ [ oxCCO ] -RF cut-off threshold of 79% within 30 min of HI predicted injury severity based on Lac/NAA with high sensitivity (100%) and specificity (93%). A significant difference in thalamic Lac/NAA was noticed (p < 0.0001) between the two groups based on this cut-off threshold of 79% Δ [ oxCCO ] -RF. The severe injury group (n = 13) had ∼30 % smaller recovery in Δ [ HbDiff ] -RF (p = 0.0001) and no significant difference was observed in Δ [ HbT ] -RF between groups. At 48 h post HI, significantly higher P31-MRS-measured inorganic phosphate/exchangeable phosphate pool (epp) (p = 0.01) and reduced phosphocreatine/epp (p = 0.003) were observed in the severe injury group indicating persistent cerebral energy depletion. Based on these results, the bNIRS measurement of the oxCCO recovery fraction offers a noninvasive real-time biomarker of brain injury severity within 30 min following HI insult.

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