Ivan Amat‐Roldan

Consorci Institut D'Investigacions Biomediques August Pi I Sunyer

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Pablo Loza‐Álvarez

Institute of Photonic Sciences

David Artigas

Universitat Politècnica de Catalunya

E. Gratacós

Consorci Institut D'Investigacions Biomediques August Pi I Sunyer

Sotiris Psilodimitrakopoulos

Foundation for Research and Technology Hellas

I.G. Cormack

Institute of Photonic Sciences

F. Figueras

Hospital Sant Joan de Déu Barcelona

Iratxe Torre

Imperial College London

Elisenda Bonet‐Carne

Universitat de Barcelona

F. Crispi

Hospital Sant Joan de Déu Barcelona

Manoj Mathew

California University of Pennsylvania

Cooperative Institutions

Leiden University Medical Center

458

University College London

404

Medical University of Graz

383

Charles University

226

Institute of Cardiology

223

Sanjay Gandhi Post Graduate Institute of Medical Sciences

210

Czech Academy of Sciences, Institute of Physiology

185

Czech Academy of Sciences

150

Medical University of Warsaw

147

University of Lucknow

146

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Effect of molecular organization on the image histograms of polarization SHG microscopy

Biomedical Optics Express (2012)

Sotiris Psilodimitrakopoulos Ivan Amat‐Roldan Pablo Loza‐Álvarez David Artigas

Based on its polarization dependency, second harmonic generation (PSHG) microscopy has been proven capable to structurally characterize molecular architectures in different biological samples. By exploiting this polarization dependency of the SHG signal in every pixel of the image, average quantitative structural information can be retrieved in the form of PSHG image histograms. In the present study we experimentally show how the PSHG image histograms can be affected by the organization of the SHG active molecules. Our experimental scenario grounds on two inherent properties of starch granules. Firstly, we take advantage of the radial organization of amylopectin molecules (the SHG source in starch) to attribute shifts of the image histograms to the existence of tilted off the plane molecules. Secondly, we use the property of starch to organize upon hydration to demonstrate that the degree of structural order at the molecular level affects the width of the PSHG image histograms. The shorter the width is the more organized the molecules in the sample are, resulting in a reliable method to measure order. The implication of this finding is crucial to the interpretation of PSHG images used for example in tissue diagnostics.

10.1364/boe.3.002681

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Citations (51)

Measurement of electric field by interferometric spectral trace observation

Optics Letters (2005)

Ivan Amat‐Roldan I.G. Cormack Pablo Loza‐Álvarez David Artigas

We present a new methodology that obtains, in an analytical way, the complex electric field of ultrashort pulses. This methodology is based only on Fourier analysis of the frequency components of spectrally resolved interferometric collinear autocorrelations. We present an experimental demonstration of this technique and the results are compared with the conventional second-harmonic generation frequency-resolved optical gating technique.

Frequency-resolved optical gating

Harmonic

TRACE (psycholinguistics)

10.1364/ol.30.001063

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Citations (38)

Ultra-short pulses to signal neuronal growth cone machinery

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2007)

Manoj Mathew Ivan Amat‐Roldan Rosa Andrés I.G. Cormack David Artigas

Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

SIGNAL (programming language)

Laser light

Growth cone

10.1117/12.699988

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Citations (0)

Front & Back Matter

Fetal Diagnosis and Therapy (2013)

Lianne Verbeek Jaap M. Middeldorp Christian V. Hulzebos D. Oepkes Frans J. Walther

10.1159/000350298

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Imaging amylopectin's order in starch using 3-dimensional polarization SHG

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2011)

Sotiris Psilodimitrakopoulos Ivan Amat‐Roldan David Artigas Pablo Loza‐Álvarez

In minimally destructive SHG biomedical imaging (high resolution optical slicing) is greatly desirable to extract the maximum of information from the light matter interaction. Here we develop a 3-D biophysical model and a methodology, which extracts molecular information below the experimental resolution limit. Firstly, it provides the pitch angle (SHG effective orientation) of the SHG source helix of the sample. This information is used to characterize and categorize the SHG sources among them. And secondly, it provides the degree of organization of the SHG source molecules. This can be used as a quantitative imaging biomarker able to characterize the degree of organization (homeostasis) of the sample. Here we applied the model in dried and hydrated wheat starch granules. Our results show that the SHG source molecule in starch is amylopectin. We also conclude that under hydration, the amylopectin molecules are further organized but they do not change structure. This organization is reflected to the width of the pitch angles pixels' histograms' distributions. The shorter the width is, the more organized the amylopectin molecules in starch are.

10.1117/12.889562

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Non-invasive measurement of HVPG using graph analysis of dynamic contrast-enhanced ultrasound: the CLEVER study

Journal of Hepatology (2018)

Annalisa Berzigotti Fabio Piscaglia Ivan Amat‐Roldan Rosa Gilabert Bogdan Procopeț

Contrast-enhanced ultrasound

Dynamic contrast

10.1016/s0168-8278(18)30372-6

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Citations (7)

25: Performance of an automatic quantitative ultrasound analysis (AQUA) texture extractor to predict fetal lung maturity assessed by TDx-FLM in amniotic fluid

American Journal of Obstetrics and Gynecology (2011)

Montse Palacio Teresa Cobo Mònica Martínez-Terrón G.A. Rattá N. Elías

Amniocentesis

10.1016/j.ajog.2011.10.051

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Citations (0)

595 Correlation Between Ultrasound Texture Analysis of the Cerebellum and Standard Diagnosis of White Matter Damage in Preterm Neonates

Pediatric Research (2010)

Elisenda Bonet‐Carne V Tenorio Ángela Arranz Ivan Amat‐Roldan E. Gratacós

Anterior fontanelle

10.1203/00006450-201011001-00595

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Citations (1)

Optical extraction of the helical pitch angle of amylopectin in starch

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2010)

Sotiris Psilodimitrakopoulos Ivan Amat‐Roldan Pablo Loza‐Álvarez David Artigas

Starch is one of the major constituents of our everyday diet and it forms granules. Starch granules are basically consisting of amylose and amylopectin molecules and they are among the brightest nature-made second harmonic generation (SHG) converters. In this study, we take advantage of that and we perform polarization sensitive SHG (PSHG) imaging of starch granules. We fit the SHG signal variation of each pixel of the PSHG images into a biophysical model and we extract molecular information below the experimental resolution limit. Specifically, by assuming that the SHG source molecule is a helix with cylindrical symmetry along its long axis, the model extracts the helical pitch angle of the SHG source and the orientation of its supporting filament for every pixel of the image. Pixel by pixel fitting consequently creates new images which their contrast is based on the values of the fitting to the theoretical model. Then we chose a region of interest in the image and we create pixels' values histograms. We applied the above in wheat starch granules and we found a highly peaked pixels' histogram of helical pitch angles at θe = 36.2°. This pitch angle corresponds to the strand of the parallel double helical structure, called amylopectin (as measured by small angle X-ray scattering). Thus, using an optical technique we extracted the helical pitch angle of amylopectin in starch. This angle value can be used as a quantitative biomarker capable of characterizing the quality of starch based structures and products.

10.1117/12.854629

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Starch-based second-harmonic-generated collinear frequency-resolved optical gating pulse characterization at the focal plane of a high-numerical-aperture lens

Optics Letters (2004)

Ivan Amat‐Roldan I.G. Cormack Pablo Loza‐Álvarez David Artigas

We report the use of starch as an ideal nonlinear medium with which to perform collinear frequency-resolved optical gating measurements of ultrashort pulses at the focal plane of a high-numerical-aperture (NA) lens. We achieved these measurements by simply sandwiching starch granules (suspended in water) between two coverslips and placing them within the focal plane of a high-NA lens. The natural nonlinear characteristics of starch allow the correct phase matching of pulses at the focal plane of a high-NA lens at different wavelengths. This elegant arrangement overcomes all the complexity and problems that were previously associated with pulse characterization within a multiphoton microscope.

Frequency-resolved optical gating

Numerical aperture

Harmonic

Aperture (computer memory)

10.1364/ol.29.002282

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Citations (33)