Recalage préservant la topologie des vaisseaux: application à la cardiologie interventionnelle

In percutaneous coronary interventions, integrating into the live fluoroscopic image vessel calcifications and occlusion information that are revealed in the pre-operative Computed Tomography Angiography can greatly improve guidance of the clinician. Fusing pre- and intra-operative information into a single space aims at taking advantage of two complementary modalities and requires a step of registration that must provide good alignment and relevant correspondences between them. Most of the existing 3D/2D vessel registration algorithms do not take into account the particular topology of the vasculature to be matched, resulting into pairings that may be topologically inconsistent along the vasculature.A first contribution consisted in a registration framework dedicated to curve matching, denoted the Iterative Closest Curve (ICC). Its main feature is to preserve the topological consistency along curves by taking advantage of the Frechet distance that not only computes the distance between two curves but also builds ordered pairings along them. A second contribution is a pairing procedure designed for the matching of a vascular tree structure that endorses its particular topology and that can easily take advantage of the ICC-framework. Centerlines of the 3D tree are matched to curves extracted from the 2D vascular graph while preserving the connectivity at 3D bifurcations. The matching criterion used to build the pairings takes into account the geometric distance and the resemblance between curves both based on a global formulation using the Frechet distance.To evaluate our approach we run experiments on a database composed of 63 clinical cases, measuring accuracy on real conditions and robustness with respect to a simulated displacement. Quantitative results have been obtained using two complementary measures that aim at assessing the results both geometrically and topologically, and quantify the resulting alignment error as well as the pairing error. The proposed method exhibits good results both in terms of pairing and alignment and demonstrates to be low sensitive to the rotations to be compensated (up to 30 degrees).Cette thèse s’inscrit dans le cadre de la cardiologie interventionnelle. Intégrer des informations telles que la position des calcifications ainsi que la taille et forme d’une occlusion dans les images fluoroscopiques constituerait un bénéfice pour le praticien. Ces informations, invisibles dans les images rayons-X pendant la procédure, sont présentes au sein du scanner CT préopératoire. La fusion de cette modalité avec la fluoroscopie apporterait une aide précieuse au guidage temps réel des outils interventionnels en bénéficiant des informations fournies par le CT. Cette fusion requiert une étape de recalage qui vise à aligner au mieux les deux modalités et fournir des correspondances pertinentes entre elles. La plupart des algorithmes de recalage 3D/2D de vaisseaux rencontrent des difficultés à construire des appariements anatomiquement pertinents, essentiellement à cause du manque de cohérence topologique le long du réseau vasculaire.Afin de résoudre ce problème, nous proposons dans cette thèse un cadre générique pour le recalage de structures curvilinéaires. L’algorithme qui en découle préserve la structure des courbes appariées. Les artères coronaires pouvant être représentées par un ensemble de courbes arrangées en arbre, nous proposons aussi une procédure d’appariement qui respecte cette structure. Le recalage d’un arbre 3D sur un graphe 2D est ainsi réalisé en assurant la préservation des connectivités aux bifurcations. Le choix de l’appariement est basé sur un critère prenant en compte la distance géométrique ainsi que la ressemblance entre courbes. Ce critère est évalué grâce à une forme modifiée de la distance de Fréchet.Une base de données de 63 cas cliniques a été utilisée à travers différentes expériences afin de prouver la robustesse et la précision de notre approche. Nous avons proposé deux mesures complémentaires visant à quantifier la qualité de l’alignement d’une part et des appariements engendrés d’autre part. La méthode proposée se montre précise pour les alignements de la projection du modèle CT et des artères coronaires observées dans les images angiographiques. De plus, les appariements obtenus sont anatomiquement pertinents et lálgorithme a prouvé sa robustesse face aux perturbations de la position initiale. Nous attribuons cette robustesse à la qualité des appariements construits au fur et à mesure des itérations

A tree-topology preserving pairing for 3D/2D registration

Information Processing in Computer-Assisted Interventions (IPCAI) 2015 Special IssueInternational audiencePurpose: Fusing pre-operative and intra-operative information into a single space aims at taking advantage of two complementary modalities and necessitates a step of registration that must provide good alignment and relevant correspondences. This paper addresses both purposes in the case of 3D/2D vessel tree matching. Method: We propose a registration algorithm endorsing this vascular tree nature by providing a pairing procedure that preserves the tree topology and by integrating this pairing into an iterative algorithm maintaining pairing coherence. In addition, we define two complementary error measures quantifying the resulting alignment error and pairing error. Both are based on manual ground-truth that is independent of the type of transformation to retrieve. Results: Experiments were conducted on a database of 63 clinical cases, evaluating robustness and accuracy of our approach with respect to the iterative closest point algorithm. Conclusion: The proposed method exhibits good results both in term of pairing and alignment as well as low sensitivity to rotations to be compensated (up to 30 degrees)

Iterative Closest Curve: a Framework for Curvilinear Structure Registration Application to 2D/3D Coronary Arteries Registration

International audienceTreatment coronary arteries endovascular involves catheter navigation through patient vasculature. The projective angiography guidance is limited in the case of chronic total occlusion where occluded vessel can not be seen. Integrating standard preoperative CT angiography information with live fluoroscopic images addresses this limitation but requires alignment of both modalities. This article proposes a structure-based registration method that intrinsically preserves both the geometrical and topological coherencies of the vascular centrelines to be registered, by the means of a dedicated curve-to-curve distance pairs of closest curves are identified, while pairing their points. Preliminary experiments demonstrate that the proposed approach performs better than the standard Iterative Closest Point method giving a wider attraction basin and improved accuracy

Topology preserving vascular registration

En cardiologie interventionnelle, le clinicien pourrait bénéficier d'une fusion de deux informations complémentaires provenant d'un scanner CT préopératoire et du flux d'images radiographiques servant au guidage des outils manipulés dans les vaisseaux du patient. Une telle fusion nécessite d'aligner les deux modalités et de construire des correspondances pertinentes. Nous proposons une approche basée sur la préservation de la topologie des structures mises en correspondance par le biais d'un cadre général visant à recaler des courbes ainsi qu'une méthode d'appariement d'arbre.In interventional cardiology, the clinician can benefit from a fused visualization of a diagnostic pre-operative CT scan and the live X-ray projective images used for the guidance of dedicated tools inside the patient's vasculature. This necessitates to align both modalities and build relevant pairings between them. We have developed a general framework combining a method to register curves with a tree pairing procedure, which is able to preserve the topology of the structures

Recalage préservant la topologie des vaisseaux: application à la cardiologie interventionnelle

In percutaneous coronary interventions, integrating into the live fluoroscopic image vessel calcifications and occlusion information that are revealed in the pre-operative Computed Tomography Angiography can greatly improve guidance of the clinician. Fusing pre- and intra-operative information into a single space aims at taking advantage of two complementary modalities and requires a step of registration that must provide good alignment and relevant correspondences between them. Most of the existing 3D/2D vessel registration algorithms do not take into account the particular topology of the vasculature to be matched, resulting into pairings that may be topologically inconsistent along the vasculature.A first contribution consisted in a registration framework dedicated to curve matching, denoted the Iterative Closest Curve (ICC). Its main feature is to preserve the topological consistency along curves by taking advantage of the Frechet distance that not only computes the distance between two curves but also builds ordered pairings along them. A second contribution is a pairing procedure designed for the matching of a vascular tree structure that endorses its particular topology and that can easily take advantage of the ICC-framework. Centerlines of the 3D tree are matched to curves extracted from the 2D vascular graph while preserving the connectivity at 3D bifurcations. The matching criterion used to build the pairings takes into account the geometric distance and the resemblance between curves both based on a global formulation using the Frechet distance.To evaluate our approach we run experiments on a database composed of 63 clinical cases, measuring accuracy on real conditions and robustness with respect to a simulated displacement. Quantitative results have been obtained using two complementary measures that aim at assessing the results both geometrically and topologically, and quantify the resulting alignment error as well as the pairing error. The proposed method exhibits good results both in terms of pairing and alignment and demonstrates to be low sensitive to the rotations to be compensated (up to 30 degrees).Cette thèse s’inscrit dans le cadre de la cardiologie interventionnelle. Intégrer des informations telles que la position des calcifications ainsi que la taille et forme d’une occlusion dans les images fluoroscopiques constituerait un bénéfice pour le praticien. Ces informations, invisibles dans les images rayons-X pendant la procédure, sont présentes au sein du scanner CT préopératoire. La fusion de cette modalité avec la fluoroscopie apporterait une aide précieuse au guidage temps réel des outils interventionnels en bénéficiant des informations fournies par le CT. Cette fusion requiert une étape de recalage qui vise à aligner au mieux les deux modalités et fournir des correspondances pertinentes entre elles. La plupart des algorithmes de recalage 3D/2D de vaisseaux rencontrent des difficultés à construire des appariements anatomiquement pertinents, essentiellement à cause du manque de cohérence topologique le long du réseau vasculaire.Afin de résoudre ce problème, nous proposons dans cette thèse un cadre générique pour le recalage de structures curvilinéaires. L’algorithme qui en découle préserve la structure des courbes appariées. Les artères coronaires pouvant être représentées par un ensemble de courbes arrangées en arbre, nous proposons aussi une procédure d’appariement qui respecte cette structure. Le recalage d’un arbre 3D sur un graphe 2D est ainsi réalisé en assurant la préservation des connectivités aux bifurcations. Le choix de l’appariement est basé sur un critère prenant en compte la distance géométrique ainsi que la ressemblance entre courbes. Ce critère est évalué grâce à une forme modifiée de la distance de Fréchet.Une base de données de 63 cas cliniques a été utilisée à travers différentes expériences afin de prouver la robustesse et la précision de notre approche. Nous avons proposé deux mesures complémentaires visant à quantifier la qualité de l’alignement d’une part et des appariements engendrés d’autre part. La méthode proposée se montre précise pour les alignements de la projection du modèle CT et des artères coronaires observées dans les images angiographiques. De plus, les appariements obtenus sont anatomiquement pertinents et lálgorithme a prouvé sa robustesse face aux perturbations de la position initiale. Nous attribuons cette robustesse à la qualité des appariements construits au fur et à mesure des itérations

How to Register a Live onto a Liver ? Partial Matching in the Space of Varifolds

30 pages, 11 figures, Special Issue: Information Processing in Medical Imaging (IPMI) 2021, Accepted for publication at the Journal of Machine Learning for Biomedical Imaging (MELBA) https://www.melba-journal.orgPartial shapes correspondences is a problem that often occurs in computer vision (occlusion, evolution in time...). In medical imaging, data may come from different modalities and be acquired under different conditions which leads to variations in shapes and topologies. In this paper we use an asymmetric data dissimilarity term applicable to various geometric shapes like sets of curves or surfaces, assessing the embedding of a shape into another one without relying on correspondences. It is designed as a data attachment for the Large Deformation Diffeomorphic Metric Mapping (LDDMM) framework, allowing to compute a meaningful deformation of one shape onto a subset of the other. We refine it in order to control the resulting non-rigid deformations and provide consistent deformations of the shapes along with their ambient space. We show that partial matching can be used for robust multi-modal liver registration between a Computed Tomography (CT) volume and a Cone Beam Computed Tomography (CBCT) volume. The 3D imaging of the patient CBCT at point of care that we call live is truncated while the CT pre-intervention provides a full visualization of the liver. The proposed method allows the truncated surfaces from CBCT to be aligned non-rigidly, yet realistically, with surfaces from CT with an average distance of 2.6mm(+/- 2.2). The generated deformations extend consistently to the liver volume, and are evaluated on points of interest for the physicians, with an average distance of 5.8mm (+/- 2.7) for vessels bifurcations and 5.13mm (+/- 2.5) for tumors landmarks. Such multi-modality volumes registrations would help the physicians in the perspective of navigating their tools in the patient's anatomy to locate structures that are hardly visible in the CBCT used during their procedures. Our code is available at https://github.com/plantonsanti/PartialMatchingVarifolds

Thin Films of Fully Noble Metal-Free POM@MOF for Photocatalytic Water Oxidation

International audienceP2 W18Co 4@MOF-545 which contains the sandwich-type polyoxometalate (POM) [(PW 9 O 34) 2 Co 4 (H 2 O) 2 ] 10-(P 2 W 18 Co 4) immobilized in the porphyrinic MOF-545 framework, is a "three-in-one" (porosity + light capture + catalysis) heterogeneous photosystem for the oxygen evolution reaction (OER). Thin films of this composite were synthesized on transparent and conductive indium tin oxide (ITO) supports using electrophoretic (EP) or drop casting (DC) methods, thus providing easy-to-use devices. Their electro-and photocatalytic activities for OER were investigated. Remarkably, both types of films exhibit higher turnover numbers (TONs) than the original bulk material previously studied as suspension for the photocatalytic OER, with TONs after 2 hours equal to 1600 and 403 for DC and EP films respectively compared to 70 for the suspension. This difference of catalytic activities is related to the proportion of efficiently illuminated crystallites, whereby a DC thin film offers the largest proportion of POM@MOF crystallites exposed to light due to its lower thickness when compared to an EP film or crystals in suspension. Such devices can be easily recycled by simply removing them from the reaction medium and washing them before reuse. The films were fully characterized with EXAFS and XANES spectroscopies, Raman, Scanning Electron Microscopy and electrochemistry, before and after catalysis. The combination of all these techniques shows the stability of both the POM and the MOF within the composite upon water oxidation reaction

Co-immobilization of a Rh Catalyst and a Keggin Polyoxometalate in the UiO-67 Zr-Based Metal–Organic Framework: In Depth Structural Characterization and Photocatalytic Properties for CO2 Reduction

International audienceThe Keggin-type polyoxometalate (POM) PW12O403– and the catalytic complex Cp*Rh(bpydc)Cl2 (bpydc = 2,2′-bipyridine-5,5′-dicarboxylic acid) were coimmobilized in the Zr(IV) based metal organic framework UiO-67. The POM is encapsulated within the cavities of the MOF by in situ synthesis, and then, the Rh catalytic complex is introduced by postsynthetic linker exchange. Infrared and Raman spectroscopies, 31P and 13C MAS NMR, N2 adsorption isotherms, and X-ray diffraction indicate the structural integrity of all components (POM, Rh-complex and MOF) within the composite of interest (PW12,Cp*Rh)@UiO-67. DFT calculations identified two possible locations of the POM in the octahedral cavities of the MOF: one at the center of a UiO-67 pore with the Cp*Rh complex pointing toward an empty pore and one off-centered with the Cp*Rh pointing toward the POM. 31P–1H heteronuclear (HETCOR) experiments ascertained the two environments of the POM, equally distributed, with the POM in interaction either with the Cp* fragment or with the organic linker. In addition, Pair Distribution Function (PDF) data were collected on the POM@MOF composite and provided key evidence of the structural integrity of the POM once immobilized into the MOF. The photocatalytic activity of the (PW12,Cp*Rh)@UiO-67 composite for CO2 reduction into formate and hydrogen were evaluated. The formate production was doubled when compared with that observed with the POM-free Cp*Rh@UiO-67 catalyst and reached TONs as high as 175 when prepared as thin films, showing the beneficial influence of the POM. Finally, the stability of the composite was assessed by means of recyclability tests. The combination of XRD, IR, ICP, and PDF experiments was essential in confirming the integrity of the POM, the catalyst, and the MOF after catalysis