40 research outputs found
Enhancing retinal images by nonlinear registration
Being able to image the human retina in high resolution opens a new era in
many important fields, such as pharmacological research for retinal diseases,
researches in human cognition, nervous system, metabolism and blood stream, to
name a few. In this paper, we propose to share the knowledge acquired in the
fields of optics and imaging in solar astrophysics in order to improve the
retinal imaging at very high spatial resolution in the perspective to perform a
medical diagnosis. The main purpose would be to assist health care
practitioners by enhancing retinal images and detect abnormal features. We
apply a nonlinear registration method using local correlation tracking to
increase the field of view and follow structure evolutions using correlation
techniques borrowed from solar astronomy technique expertise. Another purpose
is to define the tracer of movements after analyzing local correlations to
follow the proper motions of an image from one moment to another, such as
changes in optical flows that would be of high interest in a medical diagnosis.Comment: 21 pages, 7 figures, submitted to Optics Communication
Restauration myope d'images 3D par diversité de phase
Nous présentons une méthode de déconvolution 3D myope pour l'imagerie rétinienne, développée dans un contexte bayésien. Plusieurs contrainte sont utilisées, en particulier une contrainte de support en Z (issu de la technique de diversité de phase), afin de mieux contraindre le problÚme
Variational semi-blind sparse deconvolution with orthogonal kernel bases and its application to MRFM
We present a variational Bayesian method of joint image reconstruction and point spread function (PSF) estimation when the PSF of the imaging device is only partially known. To solve this semi-blind deconvolution problem, prior distributions are specified for the PSF and the 3D image. Joint image reconstruction and PSF estimation is then performed within a Bayesian framework, using a variational algorithm to estimate the posterior distribution. The image prior distribution imposes an explicit atomic measure that corresponds to image sparsity. Importantly, the proposed Bayesian deconvolution algorithm does not require hand tuning. Simulation results clearly demonstrate that the semi-blind deconvolution algorithm compares favorably with previous Markov chain Monte Carlo (MCMC) version of myopic sparse reconstruction. It significantly outperforms mismatched non-blind algorithms that rely on the assumption of the perfect knowledge of the PSF. The algorithm is illustrated on real data from magnetic resonance force microscopy (MRFM)
Restauration d'images de la rétine corrigées par optique adaptative
High resolution retinal imaging is hampered by eye's aberrations. The measurement and correction of these aberrations is made possible with an adaptive optics (AO) system. A retinal imaging bench is developped by Observatoire de Paris and is currently used in HĂŽpital des XV-XX in Paris. In wide ïŹeld imaging, the object under examination (the retina) is three-dimensional and each recorded image contains information on the object's volume. Furthermore, the AO correction is always partial and a dedicated deconvolution method is necessary to increase the images resolution and to separate numericaly the different object plans. A deconvolution method need an accurate knowledge of the point spread function (PSF) of the instrument and the tuning of several parameters named hyper parameters. In this framework, we developped two 3D deconvolution methods. The ïŹrst one use the PSF, supposed well known. The second method, which is a 3D phase diversity extension, estimates the aberrations jointly with the object. Furthermore, we developped an unsuppervised hyper parameters estimation method which is compatible with an effectiveness use of our 3D deconvolution method by non expert people. The performance of all these methods are shown on simulated retinal images and experimental data. The experimental data become from a 3D images optical bench developped at ONERA during this phD thesis.L'imagerie de la rĂ©tine, in vivo et Ă haute rĂ©solution, est rendue difïŹcile Ă cause des aberrations de l'Ćil, qui limitent la rĂ©solution. La mesure et la correction de ces aberrations sont possibles grĂące Ă l'utilisation de l'optique adaptative (OA). Un banc d'imagerie rĂ©tinienne avec OA a Ă©tĂ© dĂ©veloppĂ© par l'Observatoire de Paris et est actuellement utilisĂ© sur un panel de patients Ă l'HĂŽpital des XV-XX Ă Paris. En imagerie plein champ, le caractĂšre tridimensionnel de l'objet d'intĂ©rĂȘt (la rĂ©tine) rend l'interprĂ©tation des images difïŹcile puisque tous les plans qui constituent l'objet contribuent Ă la formation de chaque plan image. De plus, la correction par OA est toujours partielle. Il est donc nĂ©cessaire de dĂ©convoluer les images enregistrĂ©es aïŹn d'une part de sĂ©parer numĂ©riquement les plans de l'objet et d'autre part, d'amĂ©liorer la rĂ©solution latĂ©rale. Une mĂ©thode de dĂ©convolution nĂ©cessite gĂ©nĂ©ralement, pour donner des rĂ©sultats satisfaisants, d'une part une bonne connaissance de la rĂ©ponse impulsionnelle (RI) du systĂšme complet, et d'autre part un ajustement de paramĂštres de rĂ©glage appelĂ©s hyper-paramĂštres. Nous avons dĂ©veloppĂ© deux mĂ©thodes de dĂ©convolution 3D. La premiĂšre mĂ©thode suppose la RI du systĂšme connu. La deuxiĂšme est une extension tridimensionnelle de la mĂ©thode de diversitĂ© de phase et permet d'estimer la RI du systĂšme conjointement Ă l'objet d'intĂ©rĂȘt. Par ailleurs, nous avons dĂ©veloppĂ© une technique d'estimation non supervisĂ©e (« automatique ») des hyper-paramĂštres, qui permet d'envisager une utilisation efïŹcace de la dĂ©convolution 3D mĂȘme par des utilisateurs peu familiers du traitement des images tels que mĂ©decins ou biologistes. Ces mĂ©thodes ont Ă©tĂ© validĂ©es d'abord sur des donnĂ©es simulĂ©es rĂ©alistes. Ensuite nous avons dĂ©ve- loppĂ© Ă l'ONERA un banc d'imagerie 3D pour effectuer une validation expĂ©rimentale. Nous prĂ©senterons les rĂ©sultats prĂ©liminaires obtenus sur des images acquises sur ce banc
Restauration d'images de la rétine corrigées par optique adaptative
PARIS7-BibliothĂšque centrale (751132105) / SudocSudocFranceF
3D phase diversity: a myopic deconvolution method for short-exposure images: application to retinal imaging
International audienc
Enhancing retinal images by extracting structural information
International audienc
3D phase diversity: a myopic deconvolution method for short-exposure images: application to retinal imaging
International audienc