Trinocular System for 3D motion and Dense Stucture Estimation

The relief of the seafloor is an important source of data for many scientists. In this paper we present an optical system to deal with underwater 3D reconstruction. This system is formed by three cameras that take images synchronously in a constant frame rate scheme. We use the images taken by these cameras to compute dense 3D reconstructions. We use Bundle Adjustment to estimate the motion ofthe trinocular rig. Given the path followed by the system, we get a dense map of the observed scene by registering the different dense local reconstructions in a unique and bigger one

The use of 3D planning in facial surgery: Preliminary observations.

Three-dimensional (3D) planning is becoming a more commonly used tool in maxillofacial surgery. At first used only virtually, 3D planning now also enables the creation of useful intraoperative aids such as cutting guides, which decrease the operative difficulty. In our center, we have used 3D planning in various domains of facial surgery and have investigated the advantages of this technique. We have also addressed the difficulties associated with its use. 3D planning increases the accuracy of reconstructive surgery, decreases operating time, whilst maintaining excellent esthetic results. However, its use is restricted to osseous reconstruction at this stage and once planning has been undertaken, it cannot be reversed or altered intraoperatively. Despite the attractive nature of this new tool, its uses and practicalities must be further evaluated. In particular, cost-effectiveness, hospital stay, and patient perceived benefits must be assessed.

3D virtual rendering before laparoscopic partial splenectomy in children.

INTRODUCTION: Partial splenectomy in children is a good surgical option for hematological diseases and focal splenic tumors because it allows the preservation of the spleen's immunological function. Furthermore, it can be performed by laparoscopy in children as it is a safe procedure, offering the benefits of a minimally invasive approach. MATERIALS AND METHODS: The software VR-render LE version 0.81 is a system that enables the visualization of bidimentional 3D images with magnification of anatomical details. We have applied this system to five cases of non-parasitic splenic cysts before laparoscopic partial splenectomy. RESULTS: The images obtained with VR rendering software permitted the preoperative reconstruction of the vascularization of the splenic hilum, allowing the surgeon safe vessel control during laparoscopic procedures. All five partial splenectomies were carried out with no complications or major blood loss. CONCLUSIONS: Laparoscopic partial splenectomy should be a first choice procedure because it is feasible, reproducible, and safe for children; furthermore, it preserves enough splenic tissue thereby preventing post-splenectomy infections. Volume rendering provides high anatomical resolution and can be useful in guiding the surgical procedure.

Bi-planar 2D-to-3D registration in Fourier domain for stereoscopic X-ray motion tracking

In this paper we present a new method to track bonemovements in stereoscopic X-ray image series of the kneejoint. The method is based on two different X-ray imagesets: a rotational series of acquisitions of the stillsubject knee that will allow the tomographicreconstruction of the three-dimensional volume (model),and a stereoscopic image series of orthogonal projectionsas the subject performs movements. Tracking the movementsof bones throughout the stereoscopic image series meansto determine, for each frame, the best pose of everymoving element (bone) previously identified in the 3Dreconstructed model. The quality of a pose is reflectedin the similarity between its simulated projections andthe actual radiographs. We use direct Fourierreconstruction to approximate the three-dimensionalvolume of the knee joint. Then, to avoid the expensivecomputation of digitally rendered radiographs (DRR) forpose recovery, we reformulate the tracking problem in theFourier domain. Under the hypothesis of parallel X-raybeams, we use the central-slice-projection theorem toreplace the heavy 2D-to-3D registration of projections inthe signal domain by efficient slice-to-volumeregistration in the Fourier domain. Focusing onrotational movements, the translation-relevant phaseinformation can be discarded and we only consider scalarFourier amplitudes. The core of our motion trackingalgorithm can be implemented as a classical frame-wiseslice-to-volume registration task. Preliminary results onboth synthetic and real images confirm the validity ofour approach.

A history of the renewal of the corneal epithelium : a 3D animation

Background: To compare the different schemes that have been proposed during the last thirteen years to explain the renewal of the corneal epithelium. Material and Methods:We analyzed all the data present in the literature to explain the renewal of the corneal epithelium in mammals. According to the schemes proposed in the literature we developed a 3D animation to facilitate the understanding of the different concepts. Results:Three different schemes have been proposed to explain the renewal of the corneal epithelium in mammals during the last thirteen years. 1950-1981: the corneal epithelium was thought being renewed by mitosis of cells located in the basal layer. At this time scientist were not talking about stem cells. 1981-1986 was the period of the "XYZ hypothesis" or the transdifferentiation paradigm. At this time the conjunctival epithelium renewed the corneal epithelium in a centripetal migration. 1986-2008: the limbal stem cell paradigm, there were no stem cells in the corneal epithelium, all the corneal stem cells were located in the limbus and renewed the central cornea after a migration of 6 to 7 mm of transient amplifying cells toward the centre of the cornea. 2008, epithelial stem cells were found in the central cornea in mammals (Nature, Majo et al. November 2008). Discussion:We thought that the renewal of the corneal epithelium was completely defined. According to the last results we published in Nature, the current paradigm will be revisited. The experiments we made were on animals and the final demonstration on human has still to be done. If we find the same results in human, a new paradigm will be define and will change the way we consider ocular surface therapy and reconstruction.

Free-breathing 3D coronary MRA: the impact of "isotropic" image resolution.

During conventional x-ray coronary angiography, multiple projections of the coronary arteries are acquired to define coronary anatomy precisely. Due to time constraints, coronary magnetic resonance angiography (MRA) usually provides only one or two views of the major coronary vessels. A coronary MRA approach that allowed for reconstruction of arbitrary isotropic orientations might therefore be desirable. The purpose of the study was to develop a three-dimensional (3D) coronary MRA technique with isotropic image resolution in a relatively short scanning time that allows for reconstruction of arbitrary views of the coronary arteries without constraints given by anisotropic voxel size. Eight healthy adult subjects were examined using a real-time navigator-gated and corrected free-breathing interleaved echoplanar (TFE-EPI) 3D-MRA sequence. Two 3D datasets were acquired for the left and right coronary systems in each subject, one with anisotropic (1.0 x 1.5 x 3.0 mm, 10 slices) and one with "near" isotropic (1.0 x 1.5 x 1.0 mm, 30 slices) image resolution. All other imaging parameters were maintained. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and the right coronary artery (RCA) were visualized. Objective assessment of coronary vessel sharpness was similar (41% +/- 5% vs. 42% +/- 5%; P = NS) between in-plane and through-plane views with "isotropic" voxel size but differed (32% +/- 7% vs. 23% +/- 4%; P < 0.001) with nonisotropic voxel size. In reconstructed views oriented in the through-plane direction, the vessel border was 86% more defined (P < 0.01) for isotropic compared with anisotropic images. A smaller (30%; P < 0.001) improvement was seen for in-plane reconstructions. Vessel diameter measurements were view independent (2.81 +/- 0.45 mm vs. 2.66 +/- 0.52 mm; P = NS) for isotropic, but differed (2.71 +/- 0.51 mm vs. 3.30 +/- 0.38 mm; P < 0.001) between anisotropic views. Average scanning time was 2:31 +/- 0:57 minutes for anisotropic and 7:11 +/- 3:02 minutes for isotropic image resolution (P < 0.001). We present a new approach for "near" isotropic 3D coronary artery imaging, which allows for reconstruction of arbitrary views of the coronary arteries. The good delineation of the coronary arteries in all views suggests that isotropic 3D coronary MRA might be a preferred technique for the assessment of coronary disease, although at the expense of prolonged scan times. Comparative studies with conventional x-ray angiography are needed to investigate the clinical utility of the isotropic strategy.

Model-based Segmentation and Image Fusion of 3D Computed Tomography and 3D Ultrasound of the Eye for Radiotherapy Planning

For radiotherapy treatment planning of retinoblastoma inchildhood, Computed Tomography (CT) represents thestandard method for tumor volume delineation, despitesome inherent limitations. CT scan is very useful inproviding information on physical density for dosecalculation and morphological volumetric information butpresents a low sensitivity in assessing the tumorviability. On the other hand, 3D ultrasound (US) allows ahigh accurate definition of the tumor volume thanks toits high spatial resolution but it is not currentlyintegrated in the treatment planning but used only fordiagnosis and follow-up. Our ultimate goal is anautomatic segmentation of gross tumor volume (GTV) in the3D US, the segmentation of the organs at risk (OAR) inthe CT and the registration of both. In this paper, wepresent some preliminary results in this direction. Wepresent 3D active contour-based segmentation of the eyeball and the lens in CT images; the presented approachincorporates the prior knowledge of the anatomy by usinga 3D geometrical eye model. The automated segmentationresults are validated by comparing with manualsegmentations. Then, for the fusion of 3D CT and USimages, we present two approaches: (i) landmark-basedtransformation, and (ii) object-based transformation thatmakes use of eye ball contour information on CT and USimages.

3D solutions in transmission electron (Cryo) -microscopy in biology

One of the main problems in transmission electron microscopy in thebiological field is the tri-dimensionality. This article explains the technicalprocedures and requirements to prepare biological specimens preserving themclosest to their native state to perform 3D reconstruction of the macromolecularcomplexes and cellular structures in their natural environment.

Comparisons of Preoperative Three-Dimensional Planning and Surgical Reconstruction in Primary Cementless Total Hip Arthroplasty

La planification scanographique (3D) a démontré son utilité pour une reconstruction anatomique plus précise de la hanche (longueur du fémur, centre de rotation, offset, antéversion et rétroversion). Des études ont montré que lors de la planification 2D 50% seulement correspondaient à l'implant définitif du fémur alors que dans une autre étude ce taux s'élevait à 94% pour une planification 3D. Les erreurs étaient liées à l'agrandissement des radiographies. L'erreur sur la taille de la tige est liée à l'estimation inadéquate de la morphologie osseuse ainsi qu'à la densité osseuse. L'erreur de l'antéversion, augmentée par l'inclinaison du bassin, a pu être éliminée par la planification 3D et l'offset restauré dans 98%. Cette étude est basée sur une nouvelle technique de planification scanographique en trois dimensions pour une meilleure précision de la reconstruction de la hanche. Le but de cette étude est de comparer l'anatomie post-opératoire à celle préopératoire en comparant les tailles d'implant prévu lors de la planification 3D à celle réellement utilisée lors de l'opération afin de déterminer l'exactitude de la restauration anatomique avec étude des différents paramètres (centre de rotation, densité osseuse, L'offset fémoral, rotations des implants, longueur du membre) à l'aide du Logiciel HIP-PLAN (Symbios) avec évaluation de la reproductibilité de notre planification 3D dans une série prospective de 50 patients subissant une prothèse totale de hanche non cimentée primaire par voie antérieure. La planification pré-opératoire a été comparée à un CTscan postopératoire par fusion d'images. CONCLUSION ET PRESPECTIVE Les résultats obtenus sont les suivants : La taille de l'implant a été prédit correctement dans 100% des tiges, 94% des cupules et 88% des têtes (longueur). La différence entre le prévu et la longueur de la jambe postopératoire était de 0,3+2,3 mm. Les valeurs de décalage global, antéversion fémorale, inclinaison et antéversion de la cupule étaient 1,4 mm ± 3,1, 0,6 ± 3,3 0 -0,4 0 ± 5 et 6,9 ° ± 11,4, respectivement. Cette planification permet de prévoir la taille de l'implant précis. Position de la tige et de l'inclinaison de la cupule sont exactement reproductible. La planification scanographique préopératoire 3D permet une évaluation précise de l'anatomie individuelle des patients subissant une prothèse totale de hanche. La prédiction de la taille de l'implant est fiable et la précision du positionnement de la tige est excellente. Toutefois, aucun avantage n'est observée en termes d'orientation de la cupule par rapport aux études impliquant une planification 2D ou la navigation. De plus amples recherches comparant les différentes techniques de planification pré-opératoire à la navigation sont nécessaire.

Apport du CT-3D dans le diagnostic et le traitement des fractures des plateaux tibiaux [Value of 3D CT in diagnosis and treatment of fractures of the tibial plateau]

A precise classification and an optimal understanding of tibial plateau fractures are the basis of a conservative treatment or adequate surgery. The aim of this prospective study is to determine the contribution of 3D CT to the classification of fractures (comparison with standard X-rays) and as an aid to the surgeon in preoperative planning and surgical reconstruction. Between November 1994 and July 1996, 20 patients presenting 22 tibial plateau fractures were considered in this study. They all underwent surgical treatment. The fractures were classified according to the Müller AO classification. They were all investigated by means of standard X-rays (AP, profile, oblique) and the 3D CT. Analysis of the results has shown the superiority of 3D CT in the planning (easier and more acute), in the classification (more precise), and in the exact assessment of the lesions (quantity of fragments); thereby proving to be of undeniable value of the surgeon.

Surface reconstruction from microscopic images in optical lithography.

This paper presents a method to reconstruct 3D surfaces of silicon wafers from 2D images of printed circuits taken with a scanning electron microscope. Our reconstruction method combines the physical model of the optical acquisition system with prior knowledge about the shapes of the patterns in the circuit; the result is a shape-from-shading technique with a shape prior. The reconstruction of the surface is formulated as an optimization problem with an objective functional that combines a data-fidelity term on the microscopic image with two prior terms on the surface. The data term models the acquisition system through the irradiance equation characteristic of the microscope; the first prior is a smoothness penalty on the reconstructed surface, and the second prior constrains the shape of the surface to agree with the expected shape of the pattern in the circuit. In order to account for the variability of the manufacturing process, this second prior includes a deformation field that allows a nonlinear elastic deformation between the expected pattern and the reconstructed surface. As a result, the minimization problem has two unknowns, and the reconstruction method provides two outputs: 1) a reconstructed surface and 2) a deformation field. The reconstructed surface is derived from the shading observed in the image and the prior knowledge about the pattern in the circuit, while the deformation field produces a mapping between the expected shape and the reconstructed surface that provides a measure of deviation between the circuit design models and the real manufacturing process.

Pin guidance of reconstruction plate contour: an expanded role of external fixation

This article presents a modification of intraoperative external fixation for mandibular reconstruction with free tissue flaps. This technique is indicated when preregistration of the reconstruction plate is not possible due to transmandibular tumor extension. Once standard external fixation has been carried out and prior to segmental mandibulectomy, additional pins are fixed to the connecting rod that delineate the mandibular contour in three-dimensional (3D) space. Following mandibulectomy, these pins allow accurate contouring of the reconstruction plate and improved restoration of mandibular contour, projection, and dental occlusion. A step-by-step description of the technique using models and intraoperative photos is presented. This method of mandibular reconstruction is a simple and time-effective alternative to intraoperative computer navigation and 3D modeling in select cases of oral carcinoma where tumor infiltration of the outer mandibular cortex precludes prebending of the reconstruction plates.

Software for interpolation of vegetative growth of yerba mate plants in 3D

The objective of this work was to build mock-ups of complete yerba mate plants in several stages of development, using the InterpolMate software, and to compute photosynthesis on the interpolated structure. The mock-ups of yerba-mate were first built in the VPlants software for three growth stages. Male and female plants grown in two contrasting environments (monoculture and forest understory) were considered. To model the dynamic 3D architecture of yerba-mate plants during the biennial growth interval between two subsequent prunings, data sets of branch development collected in 38 dates were used. The estimated values obtained from the mock-ups, including leaf photosynthesis and sexual dimorphism, are very close to those observed in the field. However, this similarity was limited to reconstructions that included growth units from original data sets. The modeling of growth dynamics enables the estimation of photosynthesis for the entire yerba mate plant, which is not easily measurable in the field. The InterpolMate software is efficient for building yerba mate mock-ups.

Restitución 3D de la topografía de la antigua ciudad de Tarraco en un entorno SIG: propuestas metodológicas y primeros resultados

Durante los últimos años el Institut Català d’Arquelogia Clàssica, el Museu d’Història de Tarragona, contando con la colaboración de la Generalitat de Catalunya, han desarrallado el proyecto Planimetría Arqueológica de Tárraco, destinado a la elaboración de una planta arqueológica global en la cual se recogieran intervenciones y noticias referentes a los hallazgos arqueológicos existentes. Este trabajo fue publicado utilizando como plataforma de trabajo un SIG construido para tal fin (Macias et al. 2007). Sin embargo, un problema de difícil solución arqueológica venía dado por las transformaciones urbanísticas de la ciudad, sufridas en su mayor parte a lo largo de los siglos XIX y XX. Éstas habían provocado la pérdida irremediable de gran parte de la elevación que acogiera la ciudad romana, cambiando substancialmente su aspecto original. Ante esta situación y como proyecto paralelo a la realización de la Planimetría Arqueológica de Tarragona se plantearon formas de cubrir este vacío. Se presenta en esta comunicación una propuesta metodológica para la reconstrucción de los grandes «vacíos topográficos » originados por la evolución urbanística de Tarragona mediante la obtención e integración en un SIG de diversos tipos de información documental. En estas zonas rebajadas no resulta posible la obtención de información estratigráfica y arqueológica, por lo que es imprescindible la definición de vías metodológicas alternativas basadas en la extrapolación de datos extraídos de la cartografía histórica, panorámicas del XVI o fotografías tomadas en los siglos XIX y XX. Esta técnica permite aplicar los resultados obtenidos en los nuevos análisis interpretativos, complementando así la interpretación arqueológica de la topografía urbana de la ciudad romana. A partir de esta información, y aplicando funciones y técnicas de interpolación propias de un GIS, se propone aquí un modelo de relieve de la ciudad de Tarraco.

Three-Dimensional (3D) Microarchitecture Correlations with 2D Projection Image Gray-Level Variations Assessed by Trabecular Bone Score Using High-Resolution Computed Tomographic Acquisitions: Effects of Resolution and Noise.

The aim of the present study is to determine the level of correlation between the 3-dimensional (3D) characteristics of trabecular bone microarchitecture, as evaluated using microcomputed tomography (μCT) reconstruction, and trabecular bone score (TBS), as evaluated using 2D projection images directly derived from 3D μCT reconstruction (TBSμCT). Moreover, we have evaluated the effects of image degradation (resolution and noise) and X-ray energy of projection on these correlations. Thirty human cadaveric vertebrae were acquired on a microscanner at an isotropic resolution of 93μm. The 3D microarchitecture parameters were obtained using MicroView (GE Healthcare, Wauwatosa, MI). The 2D projections of these 3D models were generated using the Beer-Lambert law at different X-ray energies. Degradation of image resolution was simulated (from 93 to 1488μm). Relationships between 3D microarchitecture parameters and TBSμCT at different resolutions were evaluated using linear regression analysis. Significant correlations were observed between TBSμCT and 3D microarchitecture parameters, regardless of the resolution. Correlations were detected that were strongly to intermediately positive for connectivity density (0.711≤r(2)≤0.752) and trabecular number (0.584≤r(2)≤0.648) and negative for trabecular space (-0.407 ≤r(2)≤-0.491), up to a pixel size of 1023μm. In addition, TBSμCT values were strongly correlated between each other (0.77≤r(2)≤0.96). Study results show that the correlations between TBSμCT at 93μm and 3D microarchitecture parameters are weakly impacted by the degradation of image resolution and the presence of noise.