Prof. Ekkehard Hewer Profile

Prof. Ekkehard Hewer

at Ctr Hospitalier Univ Vaudois

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Author

Publications (12)

Proceedings Article | 19 June 2024 Presentation

Estimation of light penetration depth in human brain tissue using Mueller polarimetric imaging: ex vivo study in formalin-fixed human cerebral white and gray matter

Omar Rodríguez-Núñez, Romane Gros, Stefano Moriconi, Leonard Felger, Ekkehard Hewer, Theoni Maragkou, Richard McKinley, Angelo Pierangelo, Tatiana Novikova, Philippe Schucht

Proceedings Volume PC13010, PC1301009 (2024) https://doi.org/10.1117/12.3014418

KEYWORDS: Polarimetry, Brain tissue, Brain, Brain mapping, White matter, Visualization, Reflection, Neuroimaging, Imaging systems, Computing systems

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Proceedings Article | 18 June 2024 Presentation + Paper

Impact of histological processing on the polarimetric properties of healthy and neoplastic brain tissue

Romane Gros, Omar Rodríguez-Núñez, Leonard Felger, Stefano Moriconi, Richard McKinley, Angelo Pierangelo, Tatiana Novikova, Erik Vassella, Philippe Schucht, Ekkehard Hewer, Theoni Maragkou

Proceedings Volume 13010, 130100F (2024) https://doi.org/10.1117/12.3012928

KEYWORDS: Polarimetry, Brain tissue, Biological samples, Brain, Tumors, Depolarization, Tissues, Neuroimaging, White matter

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Proceedings Article | 3 October 2023 Presentation + Paper

Complete Mueller polarimetry: do we need it for biological tissues diagnosis?

Tatiana Novikova, Jessica Ramella-Roman, Leonard Felger, Romain Gros, Ekkehard Hewer, Theoni Maragkou, Richard McKinley, Stefano Moriconi, Michael Murek, Angelo Pierangelo, Omar Rodríguez-Núñez, Irena Zubak, Philippe Schucht

Proceedings Volume 12690, 1269006 (2023) https://doi.org/10.1117/12.2689662

KEYWORDS: Mueller matrices, Polarimetry, Depolarization, Brain, Tissues, Neuroimaging, Diagnostics, Reflection, Nervous system

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Proceedings Article | 11 August 2023 Paper

Partial Mueller polarimetry for the complete optical diagnosis of biological tissue

Proceedings Volume 12629, 1262902 (2023) https://doi.org/10.1117/12.2670094

KEYWORDS: Polarimetry, Tissues, Tissue optics, Mueller matrices, Biomedical optics, Polarization, Depolarization, Optical components, Imaging systems, Video

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SPIE Journal Paper | 24 May 2023 Open Access

Effects of formalin fixation on polarimetric properties of brain tissue: fresh or fixed?

Romain Gros, Omar Rodríguez-Núñez, Leonard Felger, Stefano Moriconi, Richard McKinley, Angelo Pierangelo, Tatiana Novikova, Erik Vassella, Philippe Schucht, Ekkehard Hewer, Theoni Maragkou

NPh, Vol. 10, Issue 02, 025009, (May 2023) https://doi.org/10.1117/12.10.1117/1.NPh.10.2.025009

KEYWORDS: Brain tissue, Polarimetry, White matter, Depolarization, Brain, Tissues, Shrinkage, Reflection, Image segmentation, Machine learning

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Proceedings Article | 15 March 2023 Presentation

Denoising diffusion networks applied to Mueller polarimetric images of brain tissue (Conference Presentation)

Stefano Moriconi, Leonard Felger, Romain Gros, Ekkehard Hewer, Theoni Maragkou, Michael Murek, Tatiana Novikova, Omar Rodríguez-Núñez, Angelo Pierangelo, Philippe Schucht, Richard McKinley

Proceedings Volume PC12382, PC123820H (2023) https://doi.org/10.1117/12.2649820

KEYWORDS: Polarimetry, Denoising, Signal to noise ratio, Neuroimaging, Diffusion, Brain, Tissues, Polarization, Visualization, Signal attenuation

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Proceedings Article | 15 March 2023 Presentation

Multi-domain cotraining for tissue segmentation in fixed and fresh brain tissue using Mueller polarimetry (Conference Presentation)

Richard McKinley, Leonard Felger, Romain Gros, Ekkehard Hewer, Theoni Maragkou, Stefano Moriconi, Michael Murek, Tatiana Novikova, Omar Rodrıguez-Nunez, Angelo Pierangelo, Philippe Schucht

Proceedings Volume PC12382, PC1238208 (2023) https://doi.org/10.1117/12.2649787

KEYWORDS: Tissues, Brain, Tissue optics, Polarimetry, Image segmentation, Neuroimaging, Visualization, Tumors, Surgery, Real time imaging

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Proceedings Article | 20 May 2022 Presentation + Paper

Machine learning for white matter fibre tract visualization in the human brain via Mueller matrix polarimetric data

Richard McKinley, Leonard Felger, Ekkehard Hewer, Theoni Maragkou, Michael Murek, Tatiana Novikova, Omar Rodríguez-Núñez, Angelo Pierangelo, Philippe Schucht

Proceedings Volume 12136, 121360G (2022) https://doi.org/10.1117/12.2624465

KEYWORDS: Brain, Polarimetry, Neuroimaging, Tissues, Tumors, Image segmentation, Visualization, Machine learning, Data modeling, Surgery

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A clear identification of the border between a brain tumor and surrounding healthy tissue during neurosurgery is essential in order to maximize tumor resection while preserving neurological function. However, tumor tissue is often difficult to differentiate from infiltrated brain during surgery. Most existing techniques have drawbacks in terms of cost, measurement time and accuracy. The fibre tracts of healthy brain white matter are composed of densely packed bundles of myelinated axons that form uniaxial linear birefringent medium with the optical axis oriented along the direction of the fibre bundle. Brain tumors, whose cells grow in a largely chaotic way, lack this anisotropy of refractive index. Therefore tumor tissue can be distinguished from of healthy white matter using polarized light. A wide-field visible wavelength imaging Mueller polarimetric system was used for the study of formalin-fixed human brain sections measured in reflection geometry. The non-linear decomposition of the Mueller matrices provided the maps of depolarization, scalar retardance and azimuth of the optical axis. A compelling correlation between the azimuth of the optical axis and the orientation of the brain fibre tracts was proven with the gold standard histology analysis. We present the results of post-processing of Mueller polarimetric images of fixed human brain sections using a combination of classical computer vision and machine learning algorithms, for the automated brain fibre tracking in the white matter tracts. Manually labelled polarimetric data was used to train a convolutional neural network to identify white matter. Within the identified white matter, surface fibre tracts could be visualized. We expect that Mueller polarimetric imaging modality combined with our ML algorithms for fibre tracking will visualize the directions of fibre tracts in imaging plane during tumor surgery, thus, allowing a neurosurgeon to orient himself, to spare essential fibre tracts and to make surgery more complete and safe.

Proceedings Article | 7 March 2022 Presentation

Brain fiber tracts imaging with polarized light: a potential navigation tool for tumor neurosurgery

Omar Rodriguez-Nunez, Philippe Schucht, Ekkehard Hewer, Tatiana Novikova, Angelo Pierangelo

Proceedings Volume PC11963, PC1196303 (2022) https://doi.org/10.1117/12.2610129

KEYWORDS: Brain, Tumors, Neuroimaging, Visualization, Tissues, Anisotropy, Refractive index, Reflection, Polarimetry, Nerve

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Proceedings Article | 7 December 2021 Paper

Retardance map of brain white matter: a potential game changer for the intra-operative navigation during brain tumor surgery

Omar Roriguez-Núñez, Philippe Schucht, Hee Ryung Lee, Mohammed Hachem Mezouar, Ekkehard Hewer, Andreas Raabe, Michael Murek, Irena Zubak, Johannes Goldberg, Enikö Kövari, Angelo Pierangelo, Tatiana Novikova

Proceedings Volume 11919, 119190Y (2021) https://doi.org/10.1117/12.2614598

KEYWORDS: Brain, Tumors, Tissue optics, Polarimetry, Neuroimaging, Brain mapping, Tissues, Surgery, Polarization, Visualization

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Proceedings Article | 5 March 2021 Presentation

Wide-field imaging of brain white matter fiber tracts with Mueller polarimetry in backscattering configuration

Philippe Schucht, Hee Ryung Lee, Mohammed Hachem Mezouar, Ekkehard Hewer, Andreas Raabe, Michael Murek, Irena Zubak, Johannes Goldberg, Enikö Kövari, Angelo Pierangelo, Tatiana Novikova

Proceedings Volume 11646, 1164605 (2021) https://doi.org/10.1117/12.2577872

KEYWORDS: Brain, Neuroimaging, Tumors, Tissue optics, Polarimetry, Backscatter, Visualization, Anisotropy, Surgery, Imaging systems

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Proceedings Article | 5 March 2021 Presentation

Wide-field imaging of brain white matter fiber tracts with Mueller polarimetry in backscattering configuration

Tatiana Novikova, Philippe Schucht, Hee Ryung Lee, Mohammed Hachem Mezouar, Ekkehard Hewer, Andreas Raabe, Michael Murek, Irena Zubak, Johannes Goldberg, Enikö Kövari, Angelo Pierangelo

Proceedings Volume 11641, 1164105 (2021) https://doi.org/10.1117/12.2588957

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Showing 5 of 12 publications

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