Archive for the 'tomography' Category

GIN plateforme Grenoble « imagerie par optique non-linéaire », microscopie intravitale

http://www-lsp.ujf-grenoble.fr/Collaborations-et-contrats

Contrat Plan état-Région 2007-2014  » Imageries biomédicales », volet « imagerie par optique non-linéaire ».

En construction : Une plateforme « Femto » en Spectro

I) Pourquoi une plateforme ? Le Laboratoire dispose actuellement de 2 chaînes laser femtoseconde Sa :Ti. (laser femtoseconde et sa pompe) L’une (n°1, sous la responsabilité de J.C. Vial, DR CNRS) est immobilisée sur la plateforme « microscopie intravitale ». Elle est utilisée à de manière intensive pour des expériences sur le petit animal en collaboration avec des biologistes, dans le cadre du nouvel Institut des Neurosciences de Grenoble. L’autre (n°2, sous la responsabilité de P. Baldeck, DR CNRS) est utilisée pour des études de caractérisation spectroscopique de molécules aux propriétés photochimiques remarquables (collaboration avec plusieurs groupes de chimistes) en liaison avec la mise au point de nouveaux marqueurs fluorescents, et plus récemment de fabrication de nanostructures métalliques et polymériques.

En parallèle avec leur utilisation principale, ces installations ont permis régulièrement ces dernières années la réalisation d’expériences de faisabilité de plusieurs projets de recherche de différentes équipes du Laboratoire et de leurs collaborateurs extérieurs (ce qui d’ailleurs a conduit certains d’entre eux à l’acquisition ultérieure de leur propre système).

De fait il est banal de dire que les propriétés des lasers à impulsions courtes en font un outil devenu un outil incontournable pour de nombreuses applications. Ces installations sont désormais (déjà !) vieillissantes et le système n°2 n’est pas compatible avec l’adaptation d’un système de « cavity dumping ».

Une troisième chaîne est en cours d’assemblage : un oscillateur laser Sa:Ti a été acheté en 2006 sur fonds propres. Le modèle choisi (Coherent Mira 900) est susceptible d’accueillir le « cavity dumping » indispensable pour les applications nécessitant les fortes puissances crêtes (effet Kerr et génération du continuum par exemple). Elle ne dispose pas pour l’instant de laser de pompe, nous en proposons l’achat dans la présente demande de financement mi-lourd.

Nous pensons en effet qu’il est essentiel de disposer d’une nouvelle plateforme complète, mise en place autour d’un club d’utilisateurs bénéficiant d’un parc d’outils et assurant un partage de compétences techniques pour
- développer de nouveaux projets de recherche dont certains sont brièvement décrits ci-dessous
- préparer la jouvence de nos installations plus anciennes, disposer d’équipements complémentaires (« cavity dumping », système de compression d’impulsion, système d’allongement de durée d’impulsion).
- pouvoir continuer à mettre à disposition de l’ensemble des chercheurs du Laboratoire ou de leurs collaborateurs une installation modernisée afin de réaliser avec un délai d’attente réduit des expériences de faisabilité, et pouvoir continuer à développer leur programme de recherche.

Cette plateforme sera couplée à plusieurs microscopes, tant pour le développement de méthodes d’imagerie non conventionnelle, que pour les applications en nanosciences ou nanobiologie. II) Projets scientifiques en cours ou futurs qui bénéficieront de la plateforme a) Microscopie optique non-linéaire pour l’investigation du vivant Intervenants : J.C. Vial et J. Douady, collaboration avec la ligne médicale de l’ESRF, le Grenoble institut des Neurosciences. A la suite de la démonstration de l’efficacité des méthodes non-linéaire classiques (2-photon et SHG) pour la microscopie intravitale [1] au sein du laboratoire, la plateforme servira à la mise en oeuvre de nouvelles méthodes d’optique non linéaire pour la microscopie du vivant, particulièrement l’effet Kerr, la génération de 3ieme harmonique et l’émission Raman cohérente.

b) Changements de phase du quartz dans la région d’opalescence par génération de second harmonique Responsable Gérard Dolino. La grande stabilité des impulsions femtosecondes issues du laser TiSa, en mode bloqué, est parfaitement adaptée à la génération de second harmonique, au sein du Quartz [2] pour sonder les changements de phase. c) Détection d’états transitoires dans les cristaux moléculaires Responsable Dominique Block. Le laser TiSa dans son mode à extraction de cavité (cavity dumping) peut conduire à la génération d’un continuum spectral utilisable dans la détection des états transitoires des cristaux moléculaires [3]. d) Spectroscopie des gaz dans les cavités à haute fréquence Responsable : Daniele Romanini. Les nombreux modes spectraux bloqués au sein des lasers TiSa femtosecondes peuvent être injectés simultanément dans des cavités à haute finesse, être doublés en fréquence et conduire à une spectroscopie de haute sensibilité [4]. e) Femtotechnologie des matériaux Intervenants : Patrice Baldeck et Olivier Stephan. Les impulsions laser femtoseconde peuvent créer de la photochimie et photopolymérisation par transition à 2 photons produisant des structures nanométriques à 3 dimensions [5] au sein de matériaux inorganiques, organiques et biologiques. f) Spectroscopie par corrélation de Fluorescence (FCS)[6] Responsable : Antoine Delon. Les transitions à 2 photons, par excitation femtoseconde, définissent efficacement des zones tri dimensionnelles favorable à la FCS . III) Description du matériel rassemblé sur la plateforme La plate-forme « Femto » possède déjà un laser femtoseconde (Achat en 2006) de type TiSa mais doit s’équiper d’un laser de pompe efficace et s’associer un environnement qui le rend utilisable sur des expériences complexes . Elle accueillera le matériel suivant, pour lequel un nécessaire multifinancement est espéré.

1) Un laser de pompe Type Millénia ou Verdi, Puissance 10W afin de pouvoir pomper 2 TiSa 60 k€ HT Objet de la présente demande 2) Laser Sa:Ti Coherent Mira 900 49k€ HT (déjà acheté sur fonds propres Labo) 2) Le doubleur et tripleur de fréquence 14 k€ HT 3) Le passage en mode picoseconde 18 k€ HT 4) Un microscope à balayage pour la mise en oeuvre de l’imagerie Kerr 35 k€ HT 5 ) Un cavity dumping 43 k€ HT 6) Un microscope à balayage pour le développement des nouvelles microscopies non-linéaire (biphoton, second harmonique, troisième harmonique, CARS) 214 k€ HT (En commun avec le CPER « imagerie biomédicale »)

IV) Plan de financement de la plateforme

60 Keuros Mi-lourd CNRS Demandé 35 Keuros Id-Nano Obtenu 49 Keuros Financement interne Obtenu 75 Keuros Financement interne + BQR Demandé 214 Keuros CPER Imagerie bio-médicale Demandé.

—-

FACILITY for Neuroimaging by Non-linear Optics

Co-Directors:

– Jean-Claude Vial, physicist, DR CNRS (Laboratory of Physical Spectrometry: “SPECTRO”, UMR UJF-CNRS 5588)

Jonathan A. Coles, physiologiste, DR CNRS (Inserm-UJF, GIN: Funtional Neuroimaging)

Boudewijn Van der Sanden, biologist for applications in neuro-oncology, CR1, (Inserm –UJF, GIN: Medical applications of synchrotron radiation)

1) Associated Staff:

Within the GIN: UJF Engineer (“Ingénieur d’études”) on transfer

Within SPECTRO: Julien Douady, Maître de Conférences, Joseph Fourier University (recruited in 2006)

A “club biphoton” has been created, it groups researchers from the various teams of the GIN. It will help in the scientific direction of the facility for neuroimaging by non-linear optics.

2) Context of the FACILITY

Why a non-linear optics facility in the GIN?

The major themes of research in the GIN concern the investigation on the nervous system in conditions such as Parkinson’s disease, epilepsies and pain, the microvasculature, particularly in brain tumors and stroke and pathological re-organization of neurons and astrocytes. These projects are mainly carried out on animal models, and involve imaging brain structures at micron scales.

The GIN has strong competences in many in vivo nuclear magnetic resonance imaging (MRI) techniques. These techniques have the advantage of being non-invasive but do not have the micron (or less) spatial resolution that is needed to image blood microvessels, cells and synapses. There are fewer functional contrast agents and markers for MRI than the increasing number of available fluorescent indicators. Therefore, in experiments on animal models, MRI is routinely complemented by histological and quantitative micromorphometric studies on fixed tissues. The GIN Teams can also image changes in intracellular free calcium concentration in the superficial layers of brain slices. Further identified needs within the GIN include: in vivo imaging of the state of cerebral vasculature in brain pathologies such as tumours or after radiation damage; rapid, high-resolution imaging of electrical activity in brain slices characteristic of pathologies such as Parkinson’s disease or epilepsy; and rapid techniques for quantitative micromorphometry. The non-linear optical techniques we have acquired, developed or are currently exploring, can meet these needs.

Non-linear optical phenomena occur when the incident light has a very high intensity. In practice, the only commercially available light source suitable for non-linear optics in neuroscience is the titanium-sapphire infrared femtosecond laser. The femtosecond laser delivers a very high peak power with an acceptable average power by producing very short pulses (< 10-13 sec). The wavelength is usually adjusted within a 700 – 1000 nm range. In neuroscience, the laser is usually the source for a two-photon microscope, in which fluorophores are excited by the simultaneous absorption of two photons. This microscope allows the imaging of fluorophores with lateral resolution of about 500 nm and an axial resolution of about 3 micron down to depths of about 600 micron in turbid materials such as brain tissue. Two-photon microscopy has been used for in vivo studies of the cortex of mice and rats through a cranial window and has allowed, for example imaging of the cortical vasculature, intracellular calcium dynamics and long-term changes in the morphology of dendritic spines.

In 2001, we set up a two-photon microscope in the Laboratoire de Spectrométrie Physique (SPECTRO) on the campus of the Université Joseph Fourier (UJF). It is routinely used for imaging the microvasculature in the cortex of the anaesthetized mouse after intravenous infusion of fluorescent molecules. A 3D image can be acquired in under less than one minute and has typically an area of 512 x 512 pixels in the horizontal plane (a pixel being 0.5 x 0.5 micron) and a depth of 200 pixels of between 1 and 3 microns.

We have developed new quantitative methods for measuring brain hemodynamics. The simultaneous use of two fluorescent probes, a large one that remains intravascular and a small one that escapes from leaky microvessels, has led to the development of a novel method of quantifying extravasation (Vérant et al 2007). These techniques have been used to characterize the damage to normal brain tissue by experimental X-ray tumour treatments being tested at the Medical Beam Line of the European Synchrotron Research Facility in Grenoble (Serduc et al 2006, Vérant et al 2007).

Non-linear phenomena can also be used for Second Harmonic Generation (SHG). Incident light on arrays of orientated molecules gives rise to emission at half the wavelength of the incident light. This second harmonic light is produced from ordered endogenous molecules such as collagen. Of more interest to neuroscience, exogenous lipophilic fluorescent molecules that insert themselves in neuronal membranes give rise to SHG that is sensitive to the membrane potential. Two laboratories have reported that, with a suitably engineered probe molecule, the SHG is considerably more sensitive to changes in membrane potential than the traditional one photon fluorescent signal (Pons et al. 2003; Millard et al. 2004) and SHG has been used to record potentials in proximal dendrites (Dombeck et al. 2005 ) and dendritic spines (Nuriya et al., 2006). Within the “Interface Physique-Science du Vivant” program of the 12th Contrat de Plan Etat-Région (CPER) a grant was obtained in 2003 for developing SHG for measurement of membrane potential with a view to imaging functional neuronal networks. A group within the Chemistry Laboratory of the Ecole Supérieure de Lyon (Chantal Andraud) is collaborating in this project in the development of new probe molecules. A dedicated SHG set-up is now available at SPECTRO (which shares the existing beam from the Ti-sapphire femtosecond laser), a PhD student (Davy Cottet) is now engaged on this subject and a grant from the “RTRA-nanosciences” has been obtained (coordinator : Julien Douady).

The experience of non-linear optical techniques applied to neuroscience that has been acquired at the SPECTRO site will make it possible to provide a facility in the new building of the Grenoble Institute of Neuroscience that will be readily useable by neuroscientists. At the same time, following the model of the successful NMR imaging platform, new techniques and applications will continue to de developed.

References

Dombeck DA, Sacconi L, Blanchard-Desce M, Webb WW (2005) Optical recording of fast neuronal membrane potential transients in acute mammalian brain slices by second-harmonic generation microscopy. J Neurophysiol 94:3628-3636

Millard AC, Jin L, Wei MD, Wuskell JP, Lewis A, Loew LM (2004) Sensitivity of second harmonic generation from styryl dyes to transmembrane potential. Biophys J 86:1169-1176.

Nuriya, M., Jiang, J., Nemet, B., Eisenthal, K. B. and Yuste, R. (2006). Imaging membrane potential in dendritic spines. Proc Natl Acad Sci U S A 103, 786-790.

Pons T, Moreaux L, Mongin O, Blanchard-Desce M, Mertz J (2003) Mechanisms of membrane potential sensing with second-harmonic generation microscopy. J Biomed Opt 8:428-431.

R. Serduc, P. Vérant, J. C. Vial, R. Farion, L. Rocas, C. Rémy, T. Fadlallah, E. Brauer, A. Bravin, J. Laissue, H. Blattmann and B. van-der-Sanden, « In vivo two-photon microscopy study of short-term effects of microbeam irradiation on normal mouse brain microvasculature, » International Journal of Radiation Oncology Biology Physics 64, 1519-1527 (2006).

3) Description of the current FACILITY

Premises: A large room with air-conditioning

Two-photon microscope adapted for in vivo imaging of mouse cortex

Infrared Ti-sapphire femtosecond laser (Spectra Physics) with pump laser and associated diagnostic measurement instruments

Confocal microscope scanning head (Bio-Rad)

Upright microscope with epi-illumination, video camera and motorized objective

Non-descanned port with two photomultipliers

Imaging software

Large motorized microscope stage

Stereotaxic frames for mice and rats

Set-up for microdissection under volatile anaesthetics

Large range of optical filters, microscope objectives and other optical elements.

Set-up for imaging by Second Harmonic Generation (SHG)

Upright microscope

Photomultipliers,

Scanning mirrors with drivers

Equipment for patch-clamping cells: micromanipulator, amplifier, software.

Experimental control and image analysis

4 PCs

Home made software for interfacing and image processing

Labview 7

Platform activities

To provide state-of-the-art two-photon microscopy for the Neuroscience, and to explore and develop new optical imaging techniques relevant to research topics of the GIN.

Scientific report

Techniques developed and used

– Measurement of blood volume and of the permeability of the blood-brain barrier to dyes in the cortex of anaesthetized mice (thesis Pascale Vérant).

– Use of multiple intravascular dyes to characterise damage to the blood-brain barrier and to cells in the parenchyma caused by synchrotron X-rays (Serduc et al, 2006) along protocols in experimental radiotherapy: micro-beams radiotherapy (cf. Serduc thesis) and photoactivation (cf. Clément Ricard thesis)

– Imaging of unfixed tissue to a depth greater than that accessible with a conventional confocal mono-photon microscope.

– Combined imaging of tissue using SHG and two-photon excited fluorescence (Clément et al., 2007)

4) ActivitY Report

Publications

Articles in peer-reviewed journals:

J. Coste, J. C. Vial, G. Faury, A. Deronzier, Y. Usson, M. Robert Nicoud and J. Verdetti, « NO synthesis, unlike respiration, influences intracellular oxygen tension, » Biochem Biophys Res Commun 290, 97-104 (2002).

R. Serduc, P. Vérant, J. C. Vial, R. Farion, L. Rocas, C. Rémy, T. Fadlallah, E. Brauer, A. Bravin, J. Laissue, H. Blattmann and B. van-der-Sanden, « In vivo two-photon microscopy study of short-term effects of microbeam irradiation on normal mouse brain microvasculature, » International Journal of Radiation Oncology Biology Physics 64, 1519-1527 (2006).

P. Vérant, R. Serduc, B. van-der-Sanden, C. Remy and J. C. Vial, « A direct method for measuring mouse capillary cortical blood volume using multiphoton laser scanning microscopy, » Journal of Cerebral Blood Flow&Metabolism 27, 1072-1081 (2007).

A. Hayek, A. Grichine, T. Huault, C. Ricard, F. Bolze, B. van der Sanden, J. C. Vial, Y. Mély, A. Duperray, P. Lilian, P. Baldeck and J. F. Nicoud, « Cell-permeant cytoplasmic blue fluorophores optimized for in vivo two-photon microscopy with low-power excitation., » Microscopy Research and Technique 70, 880-885 (2007).

P. Vérant, R. Serduc, B. van-der-Sanden, C. Remy, C. Ricard, J. A. Coles and J. C. Vial, « A subtraction method for intravital two-photon microscopy: intraparenchymal imaging and quantification of extravasation in mouse brain cortex., » Journal Of Biomedical Optics In press (2007).

C. Ricard, J. C. Vial, J. Douady and B. van-der-Sanden, « In Vivo Imaging of Elastic Fibers using Sulforhodamine B, » Journal Of Biomedical Optics In press (2007).

Book chapter:

C. Ricard, J. A. Coles, R. Serduc, B. van der Sanden, P. Vérant and J. C. Vial, in New Encyclpedia of Neurosciences, Third edition., edited by G. Adelman and B. Smith (Elsevier, 2007).

Theses:

P. Vérant, Thesis in Physical sciences, University Joseph Fourier, Grenoble, France, 2006.
Imagerie intravitale par microscopie biphotonique : application à l’étude des effets de la radiothérapie synchrotron par microfaisceaux sur la microvascularisation corticale de la souris.

R. Serduc, Thesis in Biological science, University Joseph Fourier, Grenoble, France, 2006. Effets de la radiothérapie par microfaisceaux synchrotron sur la microvascularisation cérébrale saine et tumorale chez la souris.

Congress Proceedings:

Vérant P, Serduc R, Coles JA, Farion R, Rémy C, Van der Sanden B, Vial JC (2004) A method for measuring cerebral blood volume of mouse using multiphoton laser scanning microscopy. Proc SPIE 5463:1-12.

Vérant P, Serduc R, Coles JA, Farion R, Rémy C, Van der Sanden B, Vial JC. (2005) An intravital two photon microscopy method for imaging mouse brain tissues. In: Proceedings of Imaging for Medical and Life Sciences (IMVIE2), Ilkirch, France, March 1-3, 2005.

P. Vérant, J. C. Vial, R. Serduc, C. Ricard, C. J., C. Rémy, B. van-der-Sanden, E. Brauer and A. Bravin, presented at the Biomedical Topical Meeting (BIO) Fort Lauderdale, Florida March 19, 2006 Poster Session II (ME), 2006 published in “applied-optics OSA series”.

Oral communications to international meetings:

Vérant P, Serduc R, Coles JA, Farion R, Rémy C, Van der Sanden B, Vial JC (2004) A method for measuring cerebral blood volume of mouse using multiphoton laser scanning microscopy. Photonics Europe, Strasbourg, 26 –30 avril.

Vérant P, Serduc R, Coles JA, Farion R, Rémy, C,Van der Sanden B, Vial JC. (2005), In vivo two-photon microscopy study of short-term effects of microbeam irradiation on normal mouse brain microvasculature In : Progress in biomedical Optics in Imaging, Confocal, Multiphoton, Nonlinear Microscopy Imaging II. Munich 12-16 juin 2005.

Vérant P, Serduc R, Coles JA, Farion R, Rémy C, Van der Sanden B, Vial JC. (2005) An intravital two photon microscopy method for imaging mouse brain tissues. In: IMVIE2, Ilkirch, France, March 1-3, 2005.

Vial JC, Vérant P, Serduc R, Coles JA, Farion R, Rémy C, Van der Sanden B (2007) A subtraction method for intravitaltwo-photon microscopy : intraparenchymal imaging and quantification of extravasation in mouse brain cortex. 10th International conference : « Signal transduction in the blood-brain barriers » Potsdam September 13-16 2007.

Rémy C, Serduc R,Vérant P, Vial JC, Farion R, Brauer E, Bravin A, Laissue J, Segebarth C, van der Sanden B, 2005. Effect of microbeam radiation exposure to the microvasculature of healthy mouse brain, European Association For NeuroOncology (EANO), 5-8 May, Edinburgh.

Serduc R, Farion R, Rémy C, Vérant P, Vial JC, Brauer E, Laissue J , Blattmann H, Bravin A, van der Sanden B, 2005, In vivo two photon microscopic study of short term effects of microbeam radiation therapy on the microvasculature in healthy mouse brain, European Conferences on Biomedical Optics (ECBO), (OSA meetings), 12-16 June, Munich.

Pascale Vérant, Jean Claude Vial, Raphaël Serduc, Clement Ricard, Jonathan Coles, Chantal Rémy, Elke Brauer, Alberto Bravin, Boudewijn van der Sanden. A differential in vivo 2 photon microscopy method for quantitative imaging of dye extravasation in mouse cortex, Biomedical Optical Topics meeting, OSA, Fort Lauderdale, Floride, march 2006.

Clément Ricard, Pascale Verant, Raphaël Serduc, Jean-Claude Vial, Régine Farion, Chantal Remy, Christoph Segebarth & Boudewijn van der Sanden. Multiphoton Microscopy as a Powefull Tool to Investigate the Healthy and Diseased Brain. European Bioalpine Covention, Grenoble, October 2006.

Olivier HUGON, Eric LACOT, Irina Alexandra PAUN, Boudewijn VAN DER SANDEN. Laser optical feedback microscopy, European Bioalpine Covention, Grenoble, October 2006.

Clement Ricard, Jean-Claude Vial, Sonia Teypaz, Jerome Gastaldo, Manuel Fernandez, François Estève, Christoph Segebarth & Boudewijn van der Sanden. Short-Term Effects of a 15Gy – 79keV Synchrotron Tomographic Irradiation on Healthy Mice Brain Microvasculature. ICRR San Francisco, July 2007

Boudewijn van der Sanden, Clément Ricard, Raphaël Serduc, Jean-Claude Vial, Julien Douady,Pascale Vérant, Elke Brauer-Krisch, Alberto Bravin, Jerôme Gastaldo, Manuel Fernandez, Hélène Elleaume, Herwig Requardt, Hans Blattmann, Jean Laissue, François Estève. In Vivo Two-Photon Microscopy of Cerebral Vascular Damage after Synchrotron Irradiation Protocols. Medical applications of Synchrotron Radiation MASR 2007, 25 – 29 august 2007, Saskatoon, Canada.

Mathieu Maurin, Patrice L. Baldeck, Ali Hayek, Frederic Bolze, Jean-François Nicoud, Jean-Claude Vial, Boudewijn P. J.van der Sanden, Multifunctional dye for two-photon microscopy, MRI and photon activation therapy using synchrotron irradiation, BIOS 2008, SPIE Photonic West, communication orale, paper 6867-4.

Clement Ricard, Jean-Claude Vial, Julien Douady, Boudewijn P. J.van der Sanden, Imaging elastic and collagen fibers with sulforhodamine B and second-harmonic generation, BIOS 2008, SPIE Photonic West, communication, paper 6867-23.

Oral communications to national meetings:

Coles JA, Van der Sanden B, Vial JC, Gadelle A, Leprêtre JC. (2003) Synthèse et utilisation de nouveaux marqueuers bifonctionnels détectables en microscopie biphotonique et en IRM pour l’étude des pathologies de la perfusion sanguine dans le cerveau. In: Réunion bilan du programme interdiscipolinaire CNRS-CEA- Inserm « Imagerie du petit animal », Marseille, décembre 2003.

Serduc R, Vérant P, Farion R, Vial JC, Rémy C, Brauer E, Bravin A, Van der Sanden B (2004) Microscopie à 2 photons du cerveau de souris en cours de traitement radiothérapeutique par mirco-faisceaux X. 5ème Colloque National de Diagnostic et Imagerie Optique en Médecine/Biologie, Paris (France)

Vial, Jean-Claude; Vérant, Pascale; Serduc, Raphaël; Rémy, Chantal; van der Sanden, Boudewijn P J, 2003, Imagerie par microscopie à 2 photons du cerveau de la souris. Mise au point de la méthode, des marqueurs et des applications médicales, Atelier Imagerie Optique in vivo du Petit Animal, La Tronche (France)

Vérant, Pascale; Serduc, Raphaël; Coles, Jonathan A; Farion, Régine; Rémy, Chantal; van der Sanden, Boudewijn P J; Vial, Jean-Claude, 2004, Détermination du volume capillaire cérébral des souris par microscopie à 2 photons, 5ème Colloque National de Diagnostic et Imagerie Optique en Médecine/Biologie, Paris (France)

Serduc, Raphaël; Vérant, Pascale; Vial, Jean-Claude; Farion, Régine; Rémy, Chantal; Brauer, Elke; Bravin, Alberto; Laissue, Jean A; Blattmann, Hans; Segebarth, Christoph; van der Sanden, Boudewijn P J, 2004, Anatomical and physiological changes of the microvasculature in healthy mouse brain tissue after microbeam radiation exposure, Réunion d’automne de la Société Circulation et Métabolisme Cérébral, Paris

Posters:

Coles JA, Fernandes LAL, Foucher A, Martiel JL, Vial JC (2005) Using fluorescence recovery after photobleaching (FRAP) to study glucose uptake by rat vagus nerve. Society for Neuroscience. Washington, DC 12-16 November.

Clément Ricard, Jean-Claude Vial, Julien Douady, Christoph Segebarth & Boudewijn van der Sanden. MICROSCOPIE NON LINEAIRE : DE L’HISTOLOGIE CLASSIQUE À L’HISTOLOGIE INTRAVITALE, Application au marquage des fibres élastiques in vivo. OPT-DIAG, Paris, 15/16 mai 2007.

Julien Douady, Davy Cottet, Clément Ricard, Boudewijn van der Sanden & Jean-Claude Vial. IMAGERIE DE SECOND HARMONIQUE : EN AVANT TOUTE ! OPT-DIAG, Paris, 15/16 mai 2007

Clément Ricard, Pascale Verant, Raphaël Serduc, Jean-Claude Vial, Christoph Segebarth & Boudewijn van der Sanden. Microscopie Biphotonique Intravitale et Neurosciences, Applications à l’Etude des Effets de la Photoactivation Therapy par Irradiation Synchrotron, journéé SFO, Paris, 30 Novembre 2006.

Publications for the general public

– Le journal du CNRS Juillet-Août 2005, rubrique « La vie des labos » article « Zoom dans la tête des souris ». P. Vérant et al. http://www2.cnrs.fr/presse/journal/2330.htm/

web site  : http://www-lsp.ujf-grenoble.fr/-Microscopies-intravitales-

– Le journal PAPYRUS de l’université J. Fourier : « Microscopie Intravitale »

Training

Thesis in physics: Pascale Vérant, 2006 (Dir. Jean Claude Vial and B. van der Sanden).

Two theses in biology: 1) Raphaël Serduc 2006 (Dir. Chantal Rémy and B. van der Sanden),

2) Clément Ricard 2008 (Dir. B. van der Sanden et Christoph Segebarth)

Placements: Chemistry – characterisation of new fluorescent probe molecules

Electronics – new microscope/computer interface

Optics – new scanning method for microscopy

Material sciences – New chromophors for intravital staining

Biology – Optical microscopy by Second Harmonic Generation of biological tissues

Biology – Electrical excitation of neurons

Practical labs for physics students: 3 sessions.

INSERM formation on non linear optics for microscopy.

Research Grants

Coles JA, Vial JC Mise en place d’un microscope biphotonique pour l’imagerie du cerveau de la souris. Contrat de Plan Etat-Région « Nouvelles Approches physques des Sciences du Vivant » 2000-2001 : 173 k€.

Vial JC, Coles JA Programme interdisciplinaire CNRS- Inserm -CEA » Imagerie du Petit Animal » – « Synthèse et utilisation de nouveaux marqueurs bi fonctionnels détectables en microscopie biphotonoqiue et en IRM pour l’étude des pathologies de la perfusion sanguine dans le cerveau » Nov 2002 : 36 k€

Coles JA, Vial JC. Extension d’un microscope biphotonique : la détection simultanée de fluorescence et du second harmonique. Application à l’imagerie de l’activité neuronale électrique dans le cortex cérébral de l’embryon de la souris. – CPER 2003 : 32 k€

Vial JC, van der Sanden B. – Imagerie de l’angiogénèse tumorale : de la microscopie à deux photons à l’imagerie par résonance magnétique.- CPER. 2003-2004 : 25 k€

Vial JC Soutien SPM-CNRS, équipement mi-lourd  2003 : 30 k€

Vial JC Programme « Nanobio pour la physique 2004» : 31 k€

Vial JC Développement de l’imagerie par effet Kerr, Programme de l’institut des nanosciences de Grenoble- IDNANO 2005 : 35 k€

Vial JC Elaboration de nanocristaux moléculaires fluorescents pour l’imagerie du cortex cérébral de souris par luminescence excitée à deux photons, Programme de la région Rhône Alpes CIBLE 2007 (coordinateur A. Ibanez) : 10 k€

Douady J Imagerie par génération de seconde harmonique des potentiels dendritiques. RTRA 2007 (financement pas encore communiqué).

Collaborations (Outside  GIN).

European Synchrotron Research Facility (ESRF), medical line ID17, Alberto Bravin and Elke Brauer

Laboratoire de Chimie, ENS Lyon (Chantal Andraud).

Laboratoire de Cristallographie (CNRS Grenoble, A.Ibanez).

Laboratoire de Chimie LEOPR (Organic electrochemistry and redox photochemistry laboratory (CNRS-UJF, Grenoble, A.Deronzier).

Institut de Physique et Chimie de Strasbourg (IPCMS) de STRASBOURG (UMR 7504, J.F. Nicoud)

Institut Néel, Grenoble (Catherine Villard)

CEA Grenoble, Jacques Baudier))


5) PERSPECTIVES

The facility needs to spread its activities in register with the needs of other Teams in the GIN (besides Teams 5 and 6, which are already involved in the current activities), whose scientific projects may benefit from analyses via non linear optics.

In collaboration with physicists and clinicians, the ten research teams of the GIN will investigate brain pathologies such as cerebral tumors, epilepsies and neurodegenerative diseases using both animal models and in vitro preparations. To this end, the optical techniques based on non linear optics open new prospects of addressing biological questions otherwise inaccessible. These techniques now allow analyses from the cellular level up to in vivo investigations on intact animals (intravital microscopy).

Some promising projects are listed in the following:

-a) Neuronal networks responsible for movement (Mireille Albrieux, team #10). High frequency electrical stimulation of the subthalamic nucleus is a very effective functional treatment of Parkinson’s disease. This project will identify the neural circuits that, within the basal ganglia, are involved in the pathological neuronal activity. Two-photon and intravital microscopy will help to investigate neuronal and glial cell networks involved in disturbances of basal ganglia.

-b) X synchrotron radiotherapy.(Boudewijn van der Sanden, team #6) Two protocols of experimental X-synchrotron radiotherapy: microbeam radiotherapy (MRT) and radiotherapy by photo-activation of heavy ions, such as platinum (pat-plat) will be studied in nude mouse glioma models and in healthy brain by intravital two-photon microscopy.

-c) The role of late endosomes in synaptic plasticity (Yves Goldberg, team #2). The aim is to study the impact of a mutation of Alix or CHMP2B on the morphological in situ development of dendrite spines in the cortex of KO mice. The outline of the spines will be made visible by the expression of a fluorescent protein. The use of a two-photon microscope is mandatory for such investigations.

-d) Measurement of neuronal electrical activity by second harmonic generation(SHG)(Jonathan Coles, team #5). Analysis of electrical activity in neural networks by fluorescent probes responding to membrane potential will be useful to projects (a) and (e). We will develop use of SHG, the technique that is currently the most promising, and requires a powerful femtosecond laser.

-e) Cortical generator of absence epilepsy seizures (Antoine Depaulis, team #9) .The project concerns the characterization of the cortical circuits responsible for absence seizures in a genetic rat model and their development during brain maturation. Two-photon microscopy will help in understanding the role of astrocytes during cortical maturation and the involvement of glia-neuron relationships in adults.

-f) The role of cancer stem cells in the genesis of cerebral tumors and their radiosensitivity (Jacques Baudier, CEA). Recent investigations have shown the existence of cancer stem cells endowed with the capacity to initiate and maintain cerebral tumors. The goal of the research is to: i) characterize the interactions between these cancer stem cells and the vasculature via two-photon microscopy during the genesis of glioblastomas, and ii) analyze the sensitivity of these cancer stem cells to the pat-plat protocol (see project b).

Hence, besides the prototypic installations designed and finalized in the SPECTRO laboratory, with the help of its human and financial support, in addition to its scientific expertise in physics, it looks necessary to supplement the actual installations with another machine, commercially available as a ready-to-use device, located in the GIN building, so as to be manipulated by neurobiologists with the help of expert physicists from the SPECTRO or from Teams 5 or 6, and devoted to biological applications related to questions addressed by other Teams in the GIN..

FUNDING

The facility will not contribute directly to the general overhead costs of the GIN. The platform will receive basic services (electricity, heating, cleaning, etc) but will not be further subsidized by the GIN. The platform will be financed by (1) grants (2) contributions from Teams using the platform.

Installation in the GIN and technological development

At the GIN

A two-photon microscope will be set-up with the following equipment:

Ti-sapphire femtosecond laser 150 k€

Anti-vibration table, various optical components 35 k€

Ready to use confocal microscope adapted for two photon and SHG microscopy 450 k€

Microsurgical equipment 100 k€

Total 735 k€

Technological developments

They will be done at SPECTRO where the environment is favorable.

– New non linear phenomena, promising for intravital microscopy, such as the third harmonic generation and the Kerr effect will be investigated. They need a large spectral range based on a powerful TiSa laser associated with a parametric oscillator and a cavity dumping.

450 k€

– A fast scanning unit 65 k€

Total 515 k€

Running costs

The principle running costs are incurred during collaborative biological projects, notably the purchase of animals and fluorescent probes. These costs will be covered by the collaborating biological Teams. In addition, there is the cost of maintaining the lasers and optical systems (20 k€), and the purchase of dyes for development purposes (10 k€). These costs will be covered by the program grants of the teams involved.

Publicités

GIN grenoble microscopie intravitale

http://www-lsp.ujf-grenoble.fr/-Microscopies-intravitales

Microscopies intravitales

par optique non linéaire

Nous cherchons à surpasser les inconvénients de la vidéomicroscopie classique. en utilisant l’optique non linéaire en microscopie à balayage : la microscopie biphotonique et la microscopie par génération de second harmonique.

Présentation générale : un diaporama de l’activité

Offre de stages 2008/2009

Stage M2 : Microscopie biphotonique sur ganglion sentinelle comme alternative à l’histopathologie classique

Mieux voir dans la tête des souris

A la différence de l’imagerie par résonance magnétique (IRM) et de la Tomographie par émission de positron (PET), les techniques optiques sont plus rarement applicables directement chez l’homme.

Lire la suite

Intervenants

Permanents, post-doc, doctorants et visiteurs

Lire la suite

Les dispositifs expérimentaux

La plateforme de développement de microscopie intravitale, En SPECTRO
Bientôt en SPECTRO La plateforme FEMTO en SPECTRO
Bientôt au GIN, une plateforme ouverte de microscopie intravitale

Lire la suite

Les Actualités

Une info sur les manifestations en relation avec la microscopie intravitale

Les Conférences, cours, séminaires en relation avec la microscopie intravitale. Les propositions de stage…etc

Lire la suite

Animations

La microscopie à balayage de la luminescence excitée à 2 photons de colorant injecté dans le circuit sanguin (de la souris) autorise une tomographie optique à grande profondeur (jusqu’a 0.6 mm).

Lire la suite

Présentations

Posters, Exposés…

Posters ; Exposés récents ;

Lire la suite

Collaborations et contrats

Programmes interdisciplinaires

Lire la suite

Liens et documents intéressants

en relation avec la microscopie intravitale

Lire la suite

Sous-rubriques :

GIN, Neuro-imagerie Fonctionnelle et Métabolique (Animal, Humain)

http://neurosciences.ujf-grenoble.fr/equipes/equipe5/

Responsable d’équipe :
Christoph SEGEBARTH
Adresse postale :
  • Grenoble Institut de Neurosciences
  • BP 170
  • 38042 Grenoble Cedex 9
Adresse géographique :
  • Grenoble Institut de Neurosciences
  • Bâtiment Edmond J. Safra
  • Chemin Fortuné Ferrini
  • 38700 La Tronche
  • Tél : 04.56.52.06.00
  • Tél : 04.56.52.05.99 (secrétariat)
  • mailto : christoph.segebarth@ujf-grenoble.fr

Composition de l’équipe (2008) :

Les personnels rattachés à la Plate-forme IRM sont répertoriés sous le lien Plate-forme IRM de Grenoble.
Les chercheurs « associés » à l’équipe 5 – c’est à dire accueillis dans les locaux de l’équipe pour une fraction importante de leur temps de recherche – ont leur nom précédé d’un astérisque.

Asfour Aktham, Maître de Conférence Grand Sylvie, Maïtre de Conférence – Praticien Hospitalier Pannetier Nicolas, Doctorant
Barbier Emmanuel, Chargé de Recherche INSERM Grouiller Frédéric, Doctorant Payen Jean-François, Professeur-Praticien Hospitalier
Chipon Emilie, Doctorante Jessberger Philipp, Diplomarbeit – Praticien Hospitalier Polosan Mircea, Praticien Hospitalier-Doctorant
Christen Thomas, Doctorant Kabir Yacine, Doctorant Provent Peggy, Ingénieur de Recherche CDD
Coles Jonathan, Directeur de Recherche CNRS Krainik Alexandre, Praticien Hospitalo-Universitaire Rémy Chantal, Directeur de Recherche INSERM
David Olivier, Chargé de Recherche INSERM *Lafaye de Michaux Pierre, Maître de Conférence Reyt Sébastien, Doctorant
Delon-Martin Chantal, Chargée de Recherche INSERM Lahrech Hana, Chargée de Recherche INSERM Ricard Clément, Doctorant
Detante Olivier, Doctorant Lemasson Benjamin, Doctorant Scherrer Benoît, Doctorant
Dojat Michel, Ingénieur de Recherche INSERM Leviel Jean-Louis, Professeur Segebarth Christoph, Directeur de Recheche INSERM
Doyle Senan, Post-doctorant Mauconduit Franck, Etudiant Master 2 Stupar Vasilee, Ingénieur de Recherche INSERM
Fondraz Nadège, étudiante BTSA Mayan Virginie, Etudiante Master 2 Tachrount Mohamed, Doctorant
Francony Gilles, Doctorant Naegele Bernadette, Neuropsychologue Vasseur Flor, Doctorante
Girard Pascal, Ingénieur de Recherche CDD Noack Christoph, Diplomarbeit – Université de Würzburg Warnking Jan, Chargé de Recherche INSERM
Gottschalk Michael, Post-doctorant Pachot-Clouard Mathilde, Maître de Conférence Zanoni Marie Claude, Secrétaire – gestionnaire INSERM

equipe

Axes de Recherche :

recherche

Applications biomédicales in vivo de la Résonnace Magnétique Nucléaire (RMN). Travaux effectués tant chez l’Homme que chez le petit animal (rat, souris). Ils visent au développement, à l’évaluation et à l’exploitation du potentiel de l’ensemble des méthodes de neuroimagerie RMN en neurosciences cliniques, biologiques et cognitives. En savoir plus…

Techniques usuelles :

techniques

Publications récentes :

  • Vérant P, Serduc R, Van der Sanden B, Rémy C, Ricard C, Coles JA, Vial JC. A subtraction method for intravital two-photon microscopy: intraparenchymal imaging and quantificationof extravasation in mouse brain cortex. Journal of Biomedical Optics 2008;In Press.
  • Lahrech H, Perles-Barbacaru AT, Aous S, Farion R, Le Bas J-F, Debouzy JC, Gadelle A, Fries PH. Potential of a New Contrast Agent: Gadolinium Per (3,6) Anhydro Alpha Cyclodextrin for Magnetic Resonance Neuroimaging. Journal of Cerebral Blood Flow & Metabolism 2008;In Press.
  • Feddersen B, Vercueil L, S. N, David O, Depaulis A, Deransart C. Controling seizures is not controling epilepsy : a parametric study of deep brain stimulation for epilepsy. Neurobiology of Disease 2008;In Press.
  • Grouiller F, Vercueil L, Krainik A, Segebarth C, Kahane P. A comparative study of different artefact removal algorithms for EEG signals acquired during functional MRI. Neuroimage 2008;In Press.
  • Grillon E, Provent P, Montigon O, Segebarth C, Rémy C, Barbier EL. Blood-brain barrier permeability to manganese and to Gd-DOTA in a rat model of transient cerebral ischaemia. NMR Biomed 2008;In Press.
  • Kickler N, Krack P, Fraix V, Le Bas J-F, Lamalle L, Durif F, Krainik A, Remy C, Segebarth C, Pollak P. Glutamate measurement in Parkinson’s disease using magnetic resonance spectroscopy at 3 T field strength. NMR Biomed 2008;In Press.
  • Valable S, Barbier EL, Bernaudin M, Roussel S, Segebarth C, Petit E, Remy C. In vivo MRI tracking of exogenous monocytes/macrophages targeting brain tumours in a rat model of glioma. NeuroImage 2008;In Press.
  • van der Graaf M, Julia-Sape M, Howe FA, Ziegler A, Majos C, Moreno A, Rijpkema M, Acosta DM, Opstad K, van der Meulen YM, Arus C, Heerschap A. MRS quality assessment in a multicentre study on MRS-Based classification of brain tumours. NMR Biomed 2008;21:148-158.
  • Payen J-F, Chanques G, Mantz J, Hercule C, Auriant I, Lequillou JL, Binhas M, Genty C, Rolland C, Bosson J-L. Current practices in sedation and analgesia for mechanically ventilated critically ill patients: a prospective multicenter patient-based study. Anesthesiology 2007;106(4):687-695.
  • Provent P, Benito M, Hiba B, Farion R, Lopez-Larrubia P, Ballesteros P, Rémy C, Segebarth C, Cerdan S, Coles J, Garcia-Martin ML. Serial in vivo spectroscopic nuclear magnetic resonance imaging of lactate and extracellular pH in rat gliomas shows redistribution of protons away from sites of glycolysis. Cancer Res 2007;67(16):7638-7645.
  • Stephan K, Harrison L, Kiebel SJ, David O, Penny W, Friston KJ. Dynamic causal models of neural system dynamics: current state and future extensions. J Biosci 2007;32(1):129-144.
  • Perles-Barbacaru AT, Lahrech H. A new MRI method for mapping the cerebral blood volume fraction: the rapid steady-state T(1) method. J Cereb Blood Flow Metab 2007;27(3):318-631.
  • Provent P, Kickler N, Barbier EL, Bergerot A, Farion R, Goury S, Marcaggi P, Segebarth C, Coles JA. The ammonium-induced increase in rat brain lactate concentration is rapid and reversible and suggests a physiological role of ammonium in regulating energy metabolism. J Cereb Blood Flow Metab 2007;27:1830-1840.
  • Vérant P, Serduc R, Van der Sanden B, Rémy C, Vial JC. A direct method for measuring mouse capillary cortical blood volume using multiphoton laser scanning microscopy. J Cereb Blood Flow Metab 2007;27(5):1072-1081.
  • Verdonck O, Lahrech H, Francony G, Carle O, Farion R, van de Looij Y, Rémy C, Segebarth C, Payen J-F. Erythropoietin protects from posttraumatic edema in the rat brain. J Cereb Blood Flow Metab 2007;27(7):1369-1376.
  • Guyet T, Dojat M, Garbay C. Knowledge construction from time series data using a collaborative exploration system. Journal of Biomedical Informatics 2007;40:672-687.
  • Beaumont M, Lamalle L, Segebarth C, Barbier EL. Improved K-Space Trajectory Measurement with signal Shifting. Magnetic Resonance in Medicine 2007;58(1):200-205.
  • Barrillot C, Benali H, Dojat M, Gaignard A, Gibaud B, Kinkingnéhun S, Matsumoto JP, Pelegrini-Issac M, Simon E, Temal L. Federating Distributed and Heterogeneous Information Sources in Neuroimaging: The NeuroBase Project. Stud Health Technol Inform 2007;120:3-13.
  • Testylier G, Lahrech H, Montigon O, Foquin A, Delacour C, Bernabé D, Segebarth C, Dorandeu F, Carpentier P. Cerebral edema induced in mice by a convulsive dose of soman. Evaluation through diffusion-weighted magnetic resonance imaging and histology. Toxicology and Applied Pharmacology 2007;220(2):125-137.

IOP publish. highlights of 2008

http://www.iop.org/EJ/journal/-page=extra.highlights2008/0031-9155

SPM version 8b statistical parametric mapping MATLAB

les 2 liens les plus « usefull »:

http://www.fil.ion.ucl.ac.uk/spm/software/spm8b/#Introduction

http://www.fil.ion.ucl.ac.uk/spm/doc/intro/

http://www.fil.ion.ucl.ac.uk/spm/ext/

The SPM approach in brief

The Statistical Parametric Mapping approach is voxel based:

  • Images are realigned, spatially normalised into a standard space, and smoothed.
  • Parametric statistical models are assumed at each voxel, using the General Linear Model GLM to describe the data in terms of experimental and confounding effects, and residual variability.
  • For fMRI the GLM is used in combination with a temporal convolution model.
  • Classical statistical inference is used to test hypotheses that are expressed in terms of GLM parameters. This uses an image whose voxel values are statistics, a Statistic Image, or Statistical Parametric Map (SPM{t}, SPM{Z}, SPM{F})
  • For such classical inferences, the multiple comparisons problem is addressed using continuous random field theory RFT, assuming the statistic image to be a good lattice representation of an underlying continuous stationary random field. This results in inference based on corrected p-values.
  • Bayesian inference can be used in place of classical inference resulting in Posterior Probability Maps PPMs .
  • For fMRI, analyses of effective connectivity can be implemented using Dynamic Causal Modelling DCM.

DOT-NIRS-University College London-Delpy 1999-1988

Use of mitochondrial inhibitors to demonstrate that cytochrome oxidase near-infrared spectroscopy can measure mitochondrial dysfunction noninvasively in the brain.

Cooper CE, Cope M, Springett R, Amess PN, Penrice J, Tyszczuk L, Punwani S, Ordidge R, Wyatt J, Delpy DT.

Department of Biological Sciences, University of Essex, Colchester, UK.

The use of near-infrared spectroscopy to measure noninvasively changes in the redox state of cerebral cytochrome oxidase in vivo is controversial. We therefore tested these measurements using a multiwavelength detector in the neonatal pig brain. Exchange transfusion with perfluorocarbons revealed that the spectrum of cytochrome oxidase in the near-infrared was identical in the neonatal pig, the adult rat, and in the purified enzyme. Under normoxic conditions, the neonatal pig brain contained 15 micromol/L deoxyhemoglobin, 29 micromol/L oxyhemoglobin, and 1.2 micromol/L oxidized cytochrome oxidase. The mitochondrial inhibitor cyanide was used to determine whether redox changes in cytochrome oxidase could be detected in the presence of the larger cerebral hemoglobin concentration. Addition of cyanide induced full reduction of cytochrome oxidase in both blooded and bloodless animals. In the blooded animals, subsequent anoxia caused large changes in hemoglobin oxygenation and concentration but did not affect the cytochrome oxidase near-infrared signal. Simultaneous blood oxygenation level-dependent magnetic resonance imaging measurements showed a good correlation with near-infrared measurements of deoxyhemoglobin concentration. Possible interference in the near-infrared measurements from light scattering changes was discounted by simultaneous measurements of the optical pathlength using the cerebral water absorbance as a standard chromophore. We conclude that, under these conditions, near-infrared spectroscopy can accurately measure changes in the cerebral cytochrome oxidase redox state.

Publication Types:

PMID: 9886352 [PubMed – indexed for MEDLINE]


Experimental and theoretical comparison of NIR spectroscopy measurements of cerebral hemoglobin changes.

Firbank M, Elwell CE, Cooper CE, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, London WC1E 6JA, United Kingdom CO4 3SQ.

Two near-infrared spectroscopy (NIRS) methods are available for measuring changes (Delta) in total cerebral hemoglobin concentration (CHC): 1) a continuous measurement of the changes in total hemoglobin concentration (Delta[Hb]tot) and 2) the difference between two absolute measurements of CHC, each derived from a small, controlled change in inspired O2 fraction. This paper investigates the internal consistency of these two methods by using an experimental and theoretical comparison. NIRS was used to measure [Hb]tot in five newborn piglets before and after a change in arterial PCO2. Delta[Hb]tot demonstrated a low coefficient of variation of 2.8 +/- 2.8 (SD) % which allowed changes in CO2-cerebral blood volume reactivity to be clearly discriminated. However, a high coefficient of variation of 22.8 +/- 3.5% on the DeltaCHC measurements obscured any CO2 reactivity changes. A theoretical analysis demonstrates the effects of optical pathlength, background absorption, scatter, and blood vessel diameter on both methods. For more accurate monitoring of CHC, individual measurements of optical pathlength and more accurate pulse oximetry are required.

Publication Types:

PMID: 9804599 [PubMed – indexed for MEDLINE]


A theoretical study of the signal contribution of regions of the adult head to near-infrared spectroscopy studies of visual evoked responses.

Firbank M, Okada E, Delpy DT.

University Department of Radiology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.

Near-infrared (NIR) spectroscopy has been used in studies of the cerebral hemodynamic response to visual processing. In this paper, we present theoretical results from finite element and Monte Carlo modeling in order to help understand the contribution to the NIR signal from different parts of the head. The results from the models show that at the typical optode spacings used in these studies, an infrared spectroscopy measurement of intensity is sensitive to the outer 1-2 mm of the cortical gray matter and the partial optical path length in the gray matter is approximately 10 mm, compared with a total optical path length of 400 mm. When the NIR measurement is of change in mean photon arrival time (or phase shift), the signal comes from the upper 2-4 mm of the cortical surface and there is an increased lateral spread of the contributing tissue. We predict that for a 4-cm separation of input and detection optodes at 800 nm, a 1 microM change in hemoglobin concentration in the cortex corresponds to an attenuation change of approximately 0.001 OD (optical density) or 1 ps mean time change. Movement of the brain caused by this increase in volume will cause an absorption change of approximately half this magnitude, but does not affect the photon arrival time at 4-cm spacing. A discrepancy between the predicted and the experimentally measured intensities may support the supposition that the NIR signal is actually very sensitive to changes occurring in the pial cerebral vessels lying on the brain surface.

Publication Types:

PMID: 9698577 [PubMed – indexed for MEDLINE]


The relationship of oxygen delivery to absolute haemoglobin oxygenation and mitochondrial cytochrome oxidase redox state in the adult brain: a near-infrared spectroscopy study.

Cooper CE, Delpy DT, Nemoto EM.

Department of Biological Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK. ccooper@essex.ac.uk

Near-infrared spectroscopy was used to determine the effect of changes in the rate of oxygen delivery to the adult rat brain on the absolute concentrations of oxyhaemoglobin, deoxyhaemoglobin and the redox state of the CuA centre in mitochondrial cytochrome oxidase. The cytochrome oxidase detection algorithm was determined to be robust to large changes in haemoglobin oxygenation and concentration. By assuming complete haemoglobin deoxygenation and CuA reduction following mechanical ventilation on 100% N2O, the absolute concentration of oxyhaemoglobin (35 microM), deoxyhaemoglobin (27 microM) and the redox state of CuA (82% oxidized) were calculated in the normal adult brain. The mean arterial blood pressure was decreased by exsanguination. When the pressure reached 100 mmHg, haemoglobin oxygenation started to fall, but the total haemoglobin concentration and oxidized CuA levels only fell when cerebral blood volume autoregulation mechanisms failed at 50 mmHg. Haemoglobin oxygenation fell linearly with decreases in the rate of oxygen delivery to the brain, but the oxidized CuA concentration did not start to fall until this rate was 50% of normal. The results suggest that the brain maintains more than adequate oxygen delivery to mitochondria and that near-infrared spectroscopy may be a good measure of oxygen insufficiency in vivo.

Publication Types:

PMID: 9620863 [PubMed – indexed for MEDLINE]

PMCID: PMC1219521


In vivo measurements of the wavelength dependence of tissue-scattering coefficients between 760 and 900 nm measured with time-resolved spectroscopy.

Matcher SJ, Cope M, Delpy DT.

We present in vivo values for the optical transport coefficients (mu(a), mu(s)?) of the adult human forearm, calf, and head from 760 to 900 nm measured with time-resolved spectroscopy. The accuracy of the method is tested with tissue-simulating phantoms. We obtain mu(s)?(lambda) approximately 1.1 – (5.1 x 10(-4) lambda) mm(-1) (forearm), 1.6 – (8.9 x 10(-4) lambda) mm(-1) (calf), and 1.45 – (6.5 x 10(-4) lambda) mm(-1) (head), where lambda is measured in nanometers. At 800 nm we obtain mu(a) = 0.023 +/- 0.004 mm(-1) (forearm), 0.017 +/- 0.005 mm(-1) (calf), and 0.016 +/- 0.001 mm(-1) (head). Our values differ substantially from published in vitro data. In particular, our transport coefficients for the adult head are substantially lower than previously reported values for adult human cerebral matter and pig skull cortical bone measured in vitro.

PMID: 18250686 [PubMed – in process]


Theoretical and experimental investigation of near-infrared light propagation in a model of the adult head.

Okada E, Firbank M, Schweiger M, Arridge SR, Cope M, Delpy DT.

Near-infrared light propagation in various models of the adult head is analyzed by both time-of-flight measurements and mathematical prediction. The models consist of three- or four-layered slabs, the latter incorporating a clear cerebrospinal fluid (CSF) layer. The most sophisticated model also incorporates slots that imitate sulci on the brain surface. For each model, the experimentally measured mean optical path length as a function of source-detector spacing agrees well with predictions from either a Monte Carlo model or a finite-element method based on diffusion theory or a hybrid radiosity-diffusion theory. Light propagation in the adult head is shown to be highly affected by the presence of the clear CSF layer, and both the optical path length and the spatial sensitivity profile of the models with a CSF layer are quite different from those without the CSF layer. However, the geometry of the sulci and the boundary between the gray and the white matter have little effect on the detected light distribution.

PMID: 18250644 [PubMed – in process]


The effect of scalp ischaemia on measurement of cerebral blood volume by near-infrared spectroscopy.

Owen-Reece H, Elwell CE, Wyatt JS, Delpy DT.

Department of Anaesthesia, National Hospital for Neurology and Neurosurgery, London, UK.

Near-infrared spectroscopy (NIRS) is a noninvasive method of quantifying changes in cerebral haemodynamics from changes in the absorption of near-infrared light by oxyhaemoglobin and deoxyhaemoglobin. Measurement of neonatal cerebral blood volume (CBV) by NIRS was described in 1990 but it has been suggested that, in adults, scalp and skull blood content contribute a significant amount to the cerebral haemodynamic variables quantifiable by NIRS. To investigate this, CBV was measured in nine adult subjects, in the frontal region of the head, before and after inflating a pneumatic tourniquet proximal to the measurement site. Because a change in scalp blood content could potentially alter the pathlength of light passing through the head and hence affect the measured CBV, the optical pathlength factor was therefore also measured before and after tourniquet inflation. Blood flow occlusion was confirmed by laser Doppler velocimetry. The results showed that tourniquet inflation had no effect on the estimated value of CBV or the differential pathlength factor. We conclude that, provided the distance between light entry and exit on the surface of the scalp is sufficiently large, changes in scalp blood flow have no effect on NIRS measurement of cerebral haemodynamics.

Publication Types:

PMID: 8953626 [PubMed – indexed for MEDLINE]


Comment on:

Near-infrared spectroscopy and cerebral hemodynamics.

Owen-Reece H, Smith M, Elwell CE, Goldstone JC, Delpy DT.

Publication Types:

PMID: 8706504 [PubMed – indexed for MEDLINE]


Near-infrared spectroscopy: theory and applications.

Wahr JA, Tremper KK, Samra S, Delpy DT.

Department of Anesthesiology, University of Michigan, Ann Arbor, USA.

In conclusion, NIRS appears to offer both a new monitoring modality and new information about cerebral oxygenation. Technical problems in the application of this technology persist, most notably determination of pathlength and the volume of tissue interrogated. Those familiar with the history of pulse oximetry will recall that although Millikan developed an ear oximeter in 1947, it was not until Aoyagi combined recognition of the pulse signal with spectroscopy in the 1970s that oximetry was transformed into a clinically applicable monitor. In much the same way, NIRS may find the same tremendous usefulness as a noninvasive monitor of cerebral oxygen utilization, pending resolution of the remaining technical problems.

Publication Types:

PMID: 8725427 [PubMed – indexed for MEDLINE]


The finite element method for the propagation of light in scattering media: boundary and source conditions.

Schweiger M, Arridge SR, Hiraoka M, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, England.

This paper extends our work on applying the Finite Element Method (FEM) to the propagation of light in tissue. We address herein the topics of boundary conditions and source specification for this method. We demonstrate that a variety of boundary conditions stipulated on the Radiative Transfer Equation can be implemented in a FEM approach, as well as the specification of a light source by a Neumann condition rather than an isotropic point source. We compare results for a number of different combinations of boundary and source conditions under FEM, as well as the corresponding cases in a Monte Carlo model.

Publication Types:

PMID: 8587533 [PubMed – indexed for MEDLINE]


Performance comparison of several published tissue near-infrared spectroscopy algorithms.

Matcher SJ, Elwell CE, Cooper CE, Cope M, Delpy DT.

University College London Department of Medical Physics and Bioengineering, United Kingdom.

We have collected multiwavelength near-infrared (NIR) attenuation spectra on human forearm muscle, the adult rat head, and newborn piglet head to compare the changes in chromophore concentration derived from these data using published algorithms from four groups. We find differences between the results from the algorithms on each data set, particularly in their estimation of cytochrome oxidase (cyt-aa3) redox changes. We also find some differences when applying the same algorithm to the three data sets, suggesting possible difficulties in transferring algorithms between different physiological systems (e.g., Kurth, C. D., Steven, J. M., Benaron, D., and Chance, B. (1993) J. Clin. Monit. 9, 163-170). We have also compared the algorithms using simulated data generated using measured hemoglobin absorption spectra and a diffusion model for light transport in tissue. We find that while the algorithms from three groups are in broad agreement, that published by Piantadosi (Piantadosi, C. A. (1993) Methods Toxicol. 2, 107-126) produces significantly different results for cyt-aa3 and HbO2. Either the hemoglobin spectra used to produce the simulated data are inaccurate or the modeling is incorrect, or this algorithm is erroneous.

Publication Types:

PMID: 7668392 [PubMed – indexed for MEDLINE]


The spatial resolution performance of a time-resolved optical imaging system using temporal extrapolation.

Hebden JC, Hall DJ, Delpy DT.

Department of Medical Physics, University College London, England.

Optical imaging methods are being explored as a potential means of screening for breast cancer. Previous investigations of time-resolved imaging techniques have suggested that due to the lack of photons with sufficiently small pathlengths, the spatial resolution achievable through a human breast would be unlikely to be better than a centimeter. Experimental results presented here indicate, however, that higher resolution may be achieved by extrapolating the measured temporal distribution of transmitted photons. This is performed using a least-squares fit between data and an analytic model of photon transport. The spatial resolution of a time-resolved imaging system was evaluated by measuring the edge response produced by an opaque mask embedded in the center of a 51-mm-thick, very highly scattering medium. The limiting spatial resolution was improved from about 13 mm to about 5 mm.

Publication Types:

PMID: 7565351 [PubMed – indexed for MEDLINE]


Measurement of the optical properties of the skull in the wavelength range 650-950 nm.

Firbank M, Hiraoka M, Essenpreis M, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, UK.

The optical properties of samples of bone from pig skull have been measured over the wavelength range 650-950 nm. The scattering phase function was measured on thin samples of the bone using a goniometer, and a value for the mean cosine g, of the scattering angle, was calculated. The scattering and absorption coefficients, mu s and mu a were then determined from measurements of diffuse reflectance and transmittance made with a pair of integrating spheres, by a step-wise search through a table of diffuse reflectance and transmittance versus mu a and mu s generated by a Monte Carlo model incorporating the measured scattering phase function. Values for g measured on six samples varied from 0.925 +/- 0.014 at 650 nm to 0.945 +/- 0.013 at 950 nm. Corresponding values for mu a and mu s measured on 18 samples were mu a = 0.04 +/- 0.002 mm-1, mu s = 35 +/- 0.7 mm-1 at 650 nm to mu a = 0.05 +/- 0.002 mm-1, mu s = 24 +/- 0.6 mm-1 at 950 nm.

Publication Types:

PMID: 8488176 [PubMed – indexed for MEDLINE]


Wavelength dependence of the differential pathlength factor and the log slope in time-resolved tissue spectroscopy.

Essenpreis M, Cope M, Elwell CE, Arridge SR, van der Zee P, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, UK.

Publication Types:

PMID: 8362674 [PubMed – indexed for MEDLINE]

————–

Estimation of optical pathlength through tissue from direct time of flight measurement.

Delpy DT, Cope M, van der Zee P, Arridge S, Wray S, Wyatt J.

Department of Medical Physics, University College London, UK.

Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3 +/- 0.3 times the head diameter.

Publication Types:

DOT-NIRS-University College London Delpy 2004-2000

Mapping human skeletal muscle perforator vessels using a quantum well infrared photodetector (QWIP) might explain the variability of NIRS and LDF measurements.

Binzoni T, Leung T, Delpy DT, Fauci MA, Rüfenacht D.

Department of Radiology, Faculty of Medicine, University of Geneva, Switzerland. Tiziano.Binzoni@medecine.unige.ch

Near-infrared spectroscopy (NIRS) and laser Doppler flowmetry (LDF) have become the techniques of choice allowing the non-invasive study of local human skeletal muscle metabolism and blood perfusion on a small tissue volume (a few cm3). However, it has been shown that both NIRS and LDF measurements may show a large spatial variability depending on the position of the optodes over the investigated muscle. This variability may be due to local morphologic and/or metabolic characteristics of the muscle and makes the data interpretation and comparison difficult. In the present work, we use a third method to investigate this problem which permits fast, non-invasive mapping of the intramuscular vessel distribution in the human vastus latelralis muscle. This method uses an advanced, passive, infrared imaging sensor called a QWIP (quantum well infrared photodetector). We demonstrate, using a recovery-enhanced infrared imaging technique, that there is a significant presence of perforator vessels in the region of interest of approximately 30 x 18 cm (the number of vessels being: 14, 9, 8, 33, 17 and 18 for each subject, respectively). The presence of these vessels makes the skeletal muscle highly inhomogeneous, and may explain the observed NIRS and LDF spatial variability. We conclude that accurate comparison of the metabolic activity of two different muscle regions is not possible without reliable maps of vascular ‘singularities’ such as the perforator vessels, and that the QWIP-based imaging system is one method to obtain this information.

Publication Types:

PMID: 15272688 [PubMed – indexed for MEDLINE]


Spectral characteristics of spontaneous oscillations in cerebral haemodynamics are posture dependent.

Tachtsidis I, Elwell CE, Lee CW, Leung TS, Smith M, Delpy DT.

Department of Medical Physics & Bioengineering, University College London, London WC1E 6JA, UK. iliastac@medphys.ucl.ac.uk

Publication Types:

PMID: 15174599 [PubMed – indexed for MEDLINE]


Measurement of the optical properties of the adult human head with spatially resolved spectroscopy and changes of posture.

Leung TS, Elwell CE, Tachtsidis I, Henty JR, Delpy DT.

Department of Medical Physics & Bioengineering, University College London, London WC1E 6JA, UK. tsl@medphys.ucl.ac.uk

Publication Types:

PMID: 15174596 [PubMed – indexed for MEDLINE]


Investigation of cerebral haemodynamics by near-infrared spectroscopy in young healthy volunteers reveals posture-dependent spontaneous oscillations.

Tachtsidis I, Elwell CE, Leung TS, Lee CW, Smith M, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, London WC1E 6JA, UK. iliastac@medphys.ucl.ac.uk

Autonomic reflexes enable the cardiovascular system to respond to gravitational displacement of blood during changes in posture. Spontaneous oscillations present in the cerebral and systemic circulation of healthy subjects have demonstrated a regulatory role. This study assessed the dynamic responses of the cerebral and systemic circulation upon standing up and the posture dependence of spontaneous oscillations. In ten young healthy volunteers, blood pressure and cerebral haemodynamics were continuously monitored non-invasively using the Portapres and near-infrared spectroscopy (NIRS), respectively. Oscillatory changes in the cerebral NIRS signals and the diastolic blood pressure (DBP) signal have been identified by the fast Fourier analysis. Blood pressure increased during standing and returned to basal level when volunteers sat on a chair. The mean value of cerebral tissue oxygen index (TOI) as measured by NIRS did not demonstrate any significant changes. Oscillatory changes in DBP, oxyhaemoglobin concentration [O2Hb] and TOI showed a significant increase when subjects were standing. Investigation of the low frequency component (approximately 0.1 Hz) of these fluctuations revealed posture dependence associated with activation of autonomic reflexes. Systemic and cerebral changes appeared to preserve adequate blood flow and cerebral perfusion during standing in healthy volunteers. Oscillatory changes in [O2Hb] and TOI, which may be related to the degree of cerebral sympathetic stimulation, are posture dependent in healthy subjects.

Publication Types:

PMID: 15132309 [PubMed – indexed for MEDLINE]


Monitoring cytochrome redox changes in the mitochondria of intact cells using multi-wavelength visible light spectroscopy.

Hollis VS, Palacios-Callender M, Springett RJ, Delpy DT, Moncada S.

Wolfson Institute for Biomedical Research, University College London, Cruciform Building, Gower Street, London, WC1E 6AE, UK.

We have developed an optical system based on visible light spectroscopy for the continuous study of changes in the redox states of mitochondrial cytochromes in intact mammalian cells. Cells are suspended in a closed incubation chamber in which oxygen and nitric oxide (NO) concentrations can be monitored during respiration. Simultaneously the cells are illuminated with a broad-band tungsten-halogen light source. Emergent light in the visible region (from 490-650 nm) is detected using a spectrophotometer and charge-coupled device camera system. Intensity spectra are then converted into changes in optical attenuation from a ‘steady-state’ baseline. The oxidised-minus-reduced absorption spectra of the mitochondrial cytochromes are fitted to the attenuation spectra using a multi-wavelength least-squares algorithm. Thus, the system can measure changes in the redox states of the cytochromes during cellular respiration. Here we describe this novel methodology and demonstrate its validity by monitoring the action of known respiratory chain inhibitors, including the endogenous signalling molecule NO, on cytochrome redox states in human leukocytes.

Publication Types:

PMID: 14670609 [PubMed – indexed for MEDLINE]


The oxygen dependency of cerebral oxidative metabolism in the newborn piglet studied with 31P NMRS and NIRS.

Springett RJ, Wylezinska M, Cady EB, Hollis V, Cope M, Delpy DT.

Department of Radiology, Dartmouth College, Hanover, New Hampshire, USA.

Mean cerebral saturation and changes in the oxidation state of the CuA centre of cytochrome oxidase were measured by near infra-red spectroscopy simultaneously with phosphorous metabolites and intracellular pH measured using 31P NMR spectroscopy during transient anoxia (inspired oxygen fraction = 0.0 for 105 seconds) in the newborn piglet brain. By collecting high quality 31P spectra every 10 seconds, it was possible to resolve the delay between the onset of anoxia and the fall in PCr and to show that the CuA centre of cytochrome oxidase reduced simultaneously with the fall in PCr. From these observations it is concluded that, at normoxia, oxygen tension at the mitochondrial level is substantially above a critical value at which oxidative metabolism becomes oxygen dependent.

Publication Types:

PMID: 14562751 [PubMed – indexed for MEDLINE]


Near-infrared light propagation in an adult head model. II. Effect of superficial tissue thickness on the sensitivity of the near-infrared spectroscopy signal.

Okada E, Delpy DT.

Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan. okada@elec.keio.ac.jp

It is important for near-infrared spectroscopy (NIRS) and imaging to estimate the sensitivity of the detected signal to the change in hemoglobin that results from brain activation and the volume of tissue interrogated for a specific source-detector fiber spacing. In this study light propagation in adult head models is predicted by Monte Carlo simulation to investigate the effect of the superficial tissue thickness on the partial optical path length in the brain and on the spatial sensitivity profile. In the case of source-detector spacing of 30 mm, the partial optical path length depends mainly on the depth of the inner skull surface whereas the spatial sensitivity profile is significantly affected by the thickness of the cerebrospinal fluid layer. The mean optical path length that can be measured by time-resolved experiments increases when the skull thickness increases whereas the partial mean optical path length in the brain decreases when the skull thickness increases. These results indicate that it is not appropriate to use the mean optical path length as an alternative to the partial optical path length to compensate the NIRS signal for the difference in sensitivity caused by variation of the superficial tissue thickness.

Publication Types:

PMID: 12790440 [PubMed – indexed for MEDLINE]


Near-infrared light propagation in an adult head model. I. Modeling of low-level scattering in the cerebrospinal fluid layer.

Okada E, Delpy DT.

Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan. okada@elec.keio.ac.jp

Adequate modeling of light propagation in a human head is important for quantitative near-infrared spectroscopy and optical imaging. The presence of a nonscattering cerebrospinal fluid (CSF) that surrounds the brain has been previously shown to have a strong effect on light propagation in the head. However, in reality, a small amount of scattering is caused by the arachnoid trabeculae in the CSF layer. In this study, light propagation in an adult head model with discrete scatterers distributed within the CSF layer has been predicted by Monte Carlo simulation to investigate the effect of the small amount of scattering caused by the arachnoid trabeculae in the CSF layer. This low scattering in the CSF layer is found to have little effect on the mean optical path length, a parameter that can be directly measured by a time-resolved experiment. However, the partial optical path length in brain tissue that relates the sensitivity of the detected signal to absorption changes in the brain is strongly affected by the presence of scattering within the CSF layer. The sensitivity of the near-infrared signal to hemoglobin changes induced by brain activation is improved by the effect of a low-scattering CSF layer.

Publication Types:

PMID: 12790439 [PubMed – indexed for MEDLINE]


A method for generating patient-specific finite element meshes for head modelling.

Gibson AP, Riley J, Schweiger M, Hebden JC, Arridge SR, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, UK.

Finite element modelling of fields within the body, whether electrical or optical, requires knowledge of the geometry of the object being examined. It can be clinically impractical to obtain accurate surface information for individual patients, although a limited set of measurements such as the locations of sensors attached to the body, can be acquired more readily. In this paper, we describe how a generic surface taken from an adult head is warped to fit points measured on a neonatal head surface to provide a new, individual surface from which a finite element mesh was generated. Simulations show that data generated from this mesh and from the original neonatal head surface are similar to within experimental errors. However, data generated from a mesh of the best fit sphere were significantly different from data generated from the original neonatal head surface.

Publication Types:

PMID: 12630743 [PubMed – indexed for MEDLINE]


Simultaneous measurement of cerebral tissue oxygenation over the adult frontal and motor cortex during rest and functional activation.

Leung TS, Elwell CE, Henty JR, Delpy DT.

Department of Medical Physics & Bioengineering, University College London, London, WC1E 6JA, UK.

Publication Types:

PMID: 12580459 [PubMed – indexed for MEDLINE]


Three-dimensional optical tomography of the premature infant brain.

Hebden JC, Gibson A, Yusof RM, Everdell N, Hillman EM, Delpy DT, Arridge SR, Austin T, Meek JH, Wyatt JS.

Department of Medical Physics & Bioengineering, University College London, 11-20 Capper Street, London WC1E 6JA, UK.

For the first time, three-dimensional images of the newborn infant brain have been generated using measurements of transmitted light. A 32-channel time-resolved imaging system was employed, and data were acquired using custom-made helmets which couple source fibres and detector bundles to the infant head. Images have been reconstructed using measurements of mean flight time relative to those acquired on a homogeneous reference phantom, and using a head-shaped 3D finite-element-based forward model with an external boundary constrained to match the measured positions of the sources and detectors. Results are presented for a premature infant with a cerebral haemorrhage predominantly located within the left ventricle. Images representing the distribution of absorption at 780 nm and 815 nm reveal an asymmetry consistent with the haemorrhage, and corresponding maps of blood volume and fractional oxygen saturation are generally within expected physiological values.

Publication Types:

PMID: 12502040 [PubMed – indexed for MEDLINE]


Quantitative near infrared spectroscopy measurement of cerebral hemodynamics in newborn piglets.

Brown DW, Picot PA, Naeini JG, Springett R, Delpy DT, Lee TY.

Imaging Division, Lawson Health Research Institute, London, Ontario, Canada, N6A 4V2.

Severely premature infants are often at increased risk of cerebral hemorrhage and/or ischemic injury caused by immature autoregulatory control of blood flow to the brain. If blood flow is too high, the infant is at risk of hemorrhage, whereas too little blood flow can result in ischemic injury. The development of a noninvasive, bedside means of measuring cerebral hemodynamics would greatly facilitate both diagnosis and monitoring of afflicted individuals. It is to this end that we have developed a near infrared spectroscopy (NIRS) system that allows for quantitative, bedside measurement of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique requires an i.v. injection of the near infrared chromophore indocyanine green. Six newborn piglets, median age of 18 h (range 6-54 h), median weight of 1.75 kg (range 1.5-2.1 kg), were studied. Measurements of CBF, CBV, and MTT were made at normocapnia, hypocapnia, and hypercapnia to test the technique over a range of hemodynamic conditions. The accuracy of our new approach has been determined by direct comparison with measurements made using a previously validated computed tomography technique. Paired t tests showed no significant difference between computed tomography and NIRS measurements of CBF, CBV, and MTT, and mean biases between the two methods were -2.05 mL x min(-1) x 100 g(-1), -0.18 mL x 100 g(-1), and 0.43 s, respectively. The precision of NIRS CBF, CBV, and MTT measurements, as determined by repeated-measures ANOVA, was 9.71%, 13.05%, and 7.57%, respectively.

Publication Types:

PMID: 11978878 [PubMed – indexed for MEDLINE]


Nitric oxide does not inhibit cerebral cytochrome oxidase in vivo or in the reactive hyperemic phase after brief anoxia in the adult rat.

De Visscher G, Springett R, Delpy DT, Van Reempts J, Borgers M, van Rossem K.

Department of Neuropathology, Discovery Research, Janssen Research Foundation, Turnhoutseweg 30, B-2340 Beerse, Belgium. gdvissch@janbe.jnj.com

In this study, near-infrared spectroscopy was applied to examine whether cytochrome oxidase in the rat brain is inhibited by nitric oxide in vivo. During normoxia, intravenous N(G)-nitro-L-arginine methyl ester (L-NAME) administration significantly decreased the cerebral saturation of hemoglobin with oxygen but did not alter the cytochrome oxidase redox state. Anoxia significantly reduced the cytochrome oxidase. The time course of the recovery of the redox state during reoxygenation was not altered by L-NAME. The results suggest that in adult rats, cytochrome oxidase is not inhibited by nitric oxide, either in physiologic conditions or during reoxygenation after a brief anoxic period.

PMID: 11973423 [PubMed – indexed for MEDLINE]


Local temperature changes and human skeletal muscle metabolism.

Binzoni T, Delpy D.

Departments of Radiology and Physiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.

The aim of this review is to describe the effects induced by local temperature changes on human skeletal muscle metabolism. More specifically, we will consider the influence of temperature on the mechanical properties of muscle contraction, on aerobic metabolism, anaerobic metabolism and on the Lohmann reaction. The text has been voluntarily organized on the basis of a simple bioenergetic model describing the different energy fluxes appearing in the muscle system. This approach should better highlight some of the points that still need to be investigated. Although it was not always possible to restrict the discussion to human muscle, the references report mainly data obtained directly on humans or on isolated human fibres. A short comment on skeletal muscle temperature measurement techniques, on humans, is also included.

Publication Types:

PMID: 11499164 [PubMed – indexed for MEDLINE]


Time resolved optical tomography of the human forearm.

Hillman EM, Hebden JC, Schweiger M, Dehghani H, Schmidt FE, Delpy DT, Arridge SR.

Department of Medical Physics and Bioengineering, University College London, UK.

A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise.

Publication Types:

PMID: 11324955 [PubMed – indexed for MEDLINE]


Oxygen dependency and precision of cytochrome oxidase signal from full spectral NIRS of the piglet brain.

Springett R, Newman J, Cope M, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, London WC1E 6JA, United Kingdom. rspringett@medphys.ucl.ac.uk

Oxidation changes of the copper A (Cu(A)) center of cytochrome oxidase in the brain were measured during brief anoxic swings at both normocapnia and hypercapnia (arterial PCO(2) approximately 55 mmHg). Hypercapnia increased total hemoglobin from 37.5 +/- 9.1 to 50.8 +/- 12.9 micromol/l (means +/- SD; n = 7), increased mean cerebral saturation (Smc(O(2))) from 65 +/- 4 to 77 +/- 3%, and oxidized Cu(A) by 0.43 +/- 0.23 micromol/l. During the onset of anoxia, there were no significant changes in the Cu(A) oxidation state until Smc(O(2)) had fallen to 43 +/- 5 and 21 +/- 6% at normocapnia and hypercapnia, respectively, and the maximum reduction during anoxia was not significantly different at hypercapnia (1.49 +/- 0.40 micromol/l) compared with normocapnia (1.53 +/- 0.44 micromol/l). Residuals of the least squares fitting algorithm used to convert near-infrared spectra to concentrations are presented and shown to be small compared with the component of attenuation attributed to the Cu(A) signal. From these observations, we conclude that there is minimal interference between the hemoglobin and Cu(A) signals in this model, the Cu(A) oxidation state is independent of cerebral oxygenation at normoxia, and the oxidation after hypercapnia is not the result of increased cerebral oxygenation.

Publication Types:

PMID: 11045954 [PubMed – indexed for MEDLINE]


Optical tomography in the presence of void regions

Dehghani H, Arridge SR, Schweiger M, Delpy DT.

Department of Medical Physics and Bioengineering, University College London, United Kingdom.

There is a growing interest in the use of near-infrared spectroscopy for the noninvasive determination of the oxygenation level within biological tissue. Stemming from this application, there has been further research in the use of this technique for obtaining tomographic images of the neonatal head, with the view of determining the levels of oxygenated and deoxygenated blood within the brain. Owing to computational complexity, methods used for numerical modeling of photon transfer within tissue have usually been limited to the diffusion approximation of the Boltzmann transport equation. The diffusion approximation, however, is not valid in regions of low scatter, such as the cerebrospinal fluid. Methods have been proposed for dealing with nonscattering regions within diffusing materials through the use of a radiosity-diffusion model. Currently, this new model assumes prior knowledge of the void region location; therefore it is instructive to examine the errors introduced in applying a simple diffusion-based reconstruction scheme in cases in which there exists a nonscattering region. We present reconstructed images of objects that contain a nonscattering region within a diffusive material. Here the forward data is calculated with the radiosity-diffusion model, and the inverse problem is solved with either the radiosity-diffusion model or the diffusion-only model. The reconstructed images show that even in the presence of only a thin nonscattering layer, a diffusion-only reconstruction will fail. When a radiosity-diffusion model is used for image reconstruction, together with a priori information about the position of the nonscattering region, the quality of the reconstructed image is considerably improved. The accuracy of the reconstructed images depends largely on the position of the anomaly with respect to the nonscattering region as well as the thickness of the nonscattering region.

PMID: 10975376 [PubMed – as supplied by publisher]


I MOVED THIS BLOG FROM WORDPRESS TO BLOGGER. Ce blog est à
ex-ample.blogspot.com

Blog Stats

  • 218 129 hits

localization

Flickr Photos

septembre 2018
L M M J V S D
« Oct    
 12
3456789
10111213141516
17181920212223
24252627282930
Publicités