21 research outputs found
Coronary Artery Segmentation and Motion Modelling
Conventional coronary artery bypass surgery requires invasive sternotomy and the
use of a cardiopulmonary bypass, which leads to long recovery period and has high
infectious potential. Totally endoscopic coronary artery bypass (TECAB) surgery
based on image guided robotic surgical approaches have been developed to allow the
clinicians to conduct the bypass surgery off-pump with only three pin holes incisions
in the chest cavity, through which two robotic arms and one stereo endoscopic camera
are inserted. However, the restricted field of view of the stereo endoscopic images leads
to possible vessel misidentification and coronary artery mis-localization. This results
in 20-30% conversion rates from TECAB surgery to the conventional approach.
We have constructed patient-specific 3D + time coronary artery and left ventricle
motion models from preoperative 4D Computed Tomography Angiography (CTA)
scans. Through temporally and spatially aligning this model with the intraoperative
endoscopic views of the patient's beating heart, this work assists the surgeon to identify
and locate the correct coronaries during the TECAB precedures. Thus this work has
the prospect of reducing the conversion rate from TECAB to conventional coronary
bypass procedures.
This thesis mainly focus on designing segmentation and motion tracking methods
of the coronary arteries in order to build pre-operative patient-specific motion models.
Various vessel centreline extraction and lumen segmentation algorithms are presented,
including intensity based approaches, geometric model matching method and
morphology-based method. A probabilistic atlas of the coronary arteries is formed
from a group of subjects to facilitate the vascular segmentation and registration procedures.
Non-rigid registration framework based on a free-form deformation model
and multi-level multi-channel large deformation diffeomorphic metric mapping are
proposed to track the coronary motion. The methods are applied to 4D CTA images
acquired from various groups of patients and quantitatively evaluated
Méthodes multi-organes rapides avec a priori de forme pour la localisation et la segmentation en imagerie médicale 3D
With the ubiquity of imaging in medical applications (diagnostic, treatment follow-up, surgery planning. . . ), image processing algorithms have become of primary importance. Algorithms help clinicians extract critical information more quickly and more reliably from increasingly large and complex acquisitions. In this context, anatomy localization and segmentation is a crucial component in modern clinical workflows. Due to particularly high requirements in terms of robustness, accuracy and speed, designing such tools remains a challengingtask.In this work, we propose a complete pipeline for the segmentation of multiple organs in medical images. The method is generic, it can be applied to varying numbers of organs, on different imaging modalities. Our approach consists of three components: (i) an automatic localization algorithm, (ii) an automatic segmentation algorithm, (iii) a framework for interactive corrections. We present these components as a coherent processing chain, although each block could easily be used independently of the others. To fulfill clinical requirements, we focus on robust and efficient solutions. Our anatomy localization method is based on a cascade of Random Regression Forests (Cuingnet et al., 2012). One key originality of our work is the use of shape priors for each organ (thanks to probabilistic atlases). Combined with the evaluation of the trained regression forests, they result in shape-consistent confidence maps for each organ instead of simple bounding boxes. Our segmentation method extends the implicit template deformation framework of Mory et al. (2012) to multiple organs. The proposed formulation builds on the versatility of the original approach and introduces new non-overlapping constraintsand contrast-invariant forces. This makes our approach a fully automatic, robust and efficient method for the coherent segmentation of multiple structures. In the case of imperfect segmentation results, it is crucial to enable clinicians to correct them easily. We show that our automatic segmentation framework can be extended with simple user-driven constraints to allow for intuitive interactive corrections. We believe that this final component is key towards the applicability of our pipeline in actual clinical routine.Each of our algorithmic components has been evaluated on large clinical databases. We illustrate their use on CT, MRI and US data and present a user study gathering the feedback of medical imaging experts. The results demonstrate the interest in our method and its potential for clinical use.Avec lâutilisation de plus en plus rĂ©pandue de lâimagerie dans la pratique mĂ©dicale (diagnostic, suivi, planification dâintervention, etc.), le dĂ©veloppement dâalgorithmes dâanalyse dâimages est devenu primordial. Ces algorithmes permettent aux cliniciens dâanalyser et dâinterprĂ©ter plus facilement et plus rapidement des donnĂ©es de plus en plus complexes. Dans ce contexte, la localisation et la segmentation de structures anatomiques sont devenues des composants critiques dans les processus cliniques modernes. La conception de tels outils pour rĂ©pondre aux exigences de robustesse, prĂ©cision et rapiditĂ© demeure cependant un rĂ©el dĂ©fi technique.Ce travail propose une mĂ©thode complĂšte pour la segmentation de plusieurs organes dans des images mĂ©dicales. Cette mĂ©thode, gĂ©nĂ©rique et pouvant ĂȘtre appliquĂ©e Ă un nombre variĂ© de structures et dans diffĂ©rentes modalitĂ©s dâimagerie, est constituĂ©e de trois composants : (i) un algorithme de localisation automatique, (ii) un algorithme de segmentation, (iii) un outil de correction interactive. Ces diffĂ©rentes parties peuvent sâenchaĂźner aisĂ©ment pour former un outil complet et cohĂ©rent, mais peuvent aussi bien ĂȘtre utilisĂ©es indĂ©pendemment. Lâaccent a Ă©tĂ© mis sur des mĂ©thodes robustes et efficaces afin de rĂ©pondre aux exigences cliniques. Notre mĂ©thode de localisation sâappuie sur une cascade de rĂ©gression par forĂȘts alĂ©atoires (Cuingnet et al., 2012). Elle introduit lâutilisation dâinformations a priori de forme, spĂ©cifiques Ă chaque organe (grĂące Ă des atlas probabilistes) pour des rĂ©sultats plus cohĂ©rents avec la rĂ©alitĂ© anatomique. Notre mĂ©thode de segmentation Ă©tend la mĂ©thode de segmentation par modĂšle implicite (Mory et al., 2012) Ă plusieurs modĂšles. La formulation proposĂ©e permet dâobtenir des dĂ©formations cohĂ©rentes, notamment en introduisant des contraintes de non recouvrement entre les modĂšles dĂ©formĂ©s. En sâappuyant sur des forces images polyvalentes, lâapproche proposĂ©e se montre robuste et performante pour la segmentation de multiples structures. Toute mĂ©thode automatique nâest cependant jamais parfaite. Afin que le clinicien garde la main sur le rĂ©sultat final, nous proposons dâenrichir la formulation prĂ©cĂ©dente avec des contraintes fournies par lâutilisateur. Une optimisation localisĂ©e permet dâobtenir un outil facile Ă utiliser et au comportement intuitif. Ce dernier composant est crucial pour que notre outil soit rĂ©ellement utilisable en pratique. Chacun de ces trois composants a Ă©tĂ© Ă©valuĂ© sur plusieurs grandes bases de donnĂ©es cliniques (en tomodensitomĂ©trie, imagerie par rĂ©sonance magnĂ©tique et ultrasons). Une Ă©tude avec des utilisateurs nous a aussi permis de recueillir des retours positifs de plusieurs experts en imagerie mĂ©dicale. Les diffĂ©rents rĂ©sultats prĂ©sentĂ©s dans ce manuscrit montrent lâintĂ©rĂȘt de notre mĂ©thode et son potentiel pour une utilisation clinique
Mechanics of biopolymer networks, stimuli responsive particle suspensions, and their combinations
The key aim of this thesis is to demonstrate new paradigms in designing stiffness changing soft materials. The systems developed and studied in this work have salient and unprecedented features such as (1) the ability to controllably stiffen up to 100 times (10,000 %) when exposed to an external stimulus of temperature or magnetic field, (2) the ability to uncontrollably assemble into a ultra-soft hydrogel by undergoing 10,000 fold volume expansion within 0.4 s, and (3) transformation from a repulsive colloidal glassy state to a particulate gel thus undergoing change in the dynamics and mechanical properties. With a combination of rigorous experiments and mathematical models, this thesis offers novel ways to achieve functionality in soft materials and may have numerous applications in the fields of soft robotics, defense, and direct-write additive manufacturing.
In part one of this thesis, a naturally produced biomaterial, hagfish slime is studied to understand its design principles. Hagfish slime is a unique predator defense material containing a network of long fibrous threads each 10 -15 cm in length. Hagfish releases the threads in a condensed coiled state known as skeins (⌠100 ”m), which must unravel within a fraction of a second and form a soft hydrogel to thwart a predator attack. The mechanisms of how the hagfish controls the unraveling rates, and the properties of the resulting gel are not well understood. The combined experimental and theoretical approach adopted in this thesis address these questions. First, the hypothesis that the viscous hydrodynamics may be responsible for the rapid unravelling rates is considered, and the scenario of a single skein unspooling as the fiber peels away due to viscous drag is discussed. As a result, its is shown that under reasonable physiological conditions viscous-drag-induced unravelling can occur within a few hundred milliseconds, comparable with the physiological time scales. Subsequently, through the rheological study on slime networks it is shown that key rheological and structural features of hagfish slime are insensitive to its concentration, in spite of the uncontrolled gelation process, and this peculiar characteristic may be vital for its physiological use.
In part two, the linear and nonlinear rheology of a model system of soft microgel suspensions is investigated. The interaction pair-potential between the microgel is temperature-dependent. By increasing concentration of the suspension, a transition from a viscous liquid to an entropic glass to a soft jammed state at low temperatures where the microgels interact via a repulsive potential. Increasing the temperature of the suspension beyond the Lower Critical Solution Temperature [LCST], introduces additional attractive interactions, and results in the formation of particulate gels. The competition between repulsive and attractive interactions gives a rich temperature-dependent rheological response that is also concentration-dependent. An integrated experimental and quantitative theoretical approach is presented to understand the key linear and nonlinear of the suspensions in various regimes.
In part three, two novel soft composite systems capable of unprecedented change in their mechanical properties in response to magnetic and thermal excitation are developed. The composites were formed by integrating stimuli-responsive particles (thermoresponsive microgels and magnetic particles) into the strain stiffening network of biopolymer fibrin. The interactions between the stimuli-responsive particles and biopolymer mesh is hypothesized to induces local stresses in the mesh, which inherently stiffens under the stress owing to its semiflexible nature. This helps achieve a higher sensitivity to the external field in the fabricated composites compared to the traditional flexible-polymer matrix of composite systems. Phenomenological models are developed that quantify this hypothesis, and the derived predictions are qualitatively consistent with the experimental data. This approach of using composites based on semiflexible polymers with strong inherent nonlinearity offers a promising method for developing functional materials with actively tunable mechanical propertie
Magnetic Hybrid-Materials
Externally tunable properties allow for new applications of suspensions of micro- and nanoparticles in sensors and actuators in technical and medical applications. By means of easy to generate and control magnetic fields, fluids inside of matrices are studied. This monnograph delivers the latest insigths into multi-scale modelling, manufacturing and application of those magnetic hybrid materials
Magnetic Hybrid-Materials
Externally tunable properties allow for new applications of suspensions of micro- and nanoparticles in sensors and actuators in technical and medical applications. By means of easy to generate and control magnetic fields, fluids inside of matrices are studied. This monnograph delivers the latest insigths into multi-scale modelling, manufacturing and application of those magnetic hybrid materials
Critical Thinking Skills Profile of High School Students In Learning Science-Physics
This study aims to describe Critical Thinking Skills high school students in the city of Makassar. To achieve this goal, the researchers conducted an analysis of student test results of 200 people scattered in six schools in the city of Makassar. The results of the quantitative descriptive analysis of the data found that the average value of students doing the interpretation, analysis, and inference in a row by 1.53, 1.15, and 1.52. This value is still very low when compared with the maximum value that may be obtained by students, that is equal to 10.00. This shows that the critical thinking skills of high school students are still very low. One fact Competency Standards science subjects-Physics is demonstrating the ability to think logically, critically, and creatively with the guidance of teachers and demonstrate the ability to solve simple problems in daily life. In fact, according to Michael Scriven stated that the main task of education is to train students and or students to think critically because of the demands of work in the global economy, the survival of a democratic and personal decisions and decisions in an increasingly complex society needs people who can think well and make judgments good. Therefore, the need for teachers in the learning device scenario such as: driving question or problem, authentic Investigation: Science Processes
Advanced Applications of Rapid Prototyping Technology in Modern Engineering
Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems
Strategies for teaching engineering mathematics
This thesis is an account of experiments into the teaching of mathematics
to engineering undergraduates which have been conducted over twenty
years against a background of changing intake ability, varying output
requirements and increasing restrictions on the formal contact time
available.
The aim has been to improve the efficiency of the teaching-learning
process.
The main areas of experimentation have been the integration in the
syllabus of numerical and analytical methods, the incorporation of case
studies into the curriculum and the use of micro-based software to enhance
the teaching process.
Special attention is paid to courses in Mathematical Engineering and their
position in the spectrum of engineering disciplines.
A core curriculum in mathematics for undergraduate engineers is
proposed and details are provided of its implementation. The roles of case
studies and micro-based software are highlighted. The provision of a
mathematics learning resource centre is considered a necessary feature of
the implementation of the proposed course. Finally, suggestions for
further research are made