110 research outputs found
Evaluation of the results of orthodontic treatment by non-rigid image registration and deformation-based morphometry
The goal of this research was to find out, whether the non-rigid registration of dental casts can be used in the evaluation of orthodontic treatment and to develop a program, which would at least partially automatize the evaluation process of images. The aim was also to experiment the evaluation of three-dimensional models of the casts. This research was delimited to cover only the evaluation of malocclusions within the dental arch. The relationships between the dental arches were not considered. This thesis was done in the University of Vaasa at the Department of Electrical Engineering and Energy Technology as a part of the HammasSkanneri research project, whose aim is to automatize the digitization and archiving of dental casts.
This research used two-dimensional images of dental casts which were taken of orthodontically treated patients before and after orthodontic treatment. Non-rigid registration was performed by using a registration tool of Fiji software. The evaluation of the accuracy of the registration was performed by measuring distances between manually inserted landmarks, and by comparing the linear and angular parameters of the registered images and the original target images. The displacements of the teeth were approximated with the help of deformation-based morphometry.
The accuracy of registration is within reasonable error limits, if the image is taken straight from above of the cast and the registration is performed with the help of landmarks inserted by a human. Estimation of the changes showed that the movement of teeth can be coarsely measured by using deformation-based morphometry based on change estimates that resemble the Jacobian estimates. A set of programs, which partially automatize the evaluation of the accuracy and the changes, were developed. Three-dimensional imaging of the casts was unsuccessful, and thus the development of 3D evaluation system was left as a future research topic.fi=OpinnÀytetyö kokotekstinÀ PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=LÀrdomsprov tillgÀngligt som fulltext i PDF-format
Shape classification: towards a mathematical description of the face
Recent advances in biostereometric techniques have led to the quick and easy
acquisition of 3D data for facial and other biological surfaces. This has led facial
surgeons to express dissatisfaction with landmark-based methods for analysing the
shape of the face which use only a small part of the data available, and to seek a method
for analysing the face which maximizes the use of this extensive data set. Scientists
working in the field of computer vision have developed a variety of methods for the
analysis and description of 2D and 3D shape. These methods are reviewed and an
approach, based on differential geometry, is selected for the description of facial shape.
For each data point, the Gaussian and mean curvatures of the surface are calculated.
The performance of three algorithms for computing these curvatures are evaluated for
mathematically generated standard 3D objects and for 3D data obtained from an optical
surface scanner. Using the signs of these curvatures, the face is classified into eight
'fundamental surface types' - each of which has an intuitive perceptual meaning. The
robustness of the resulting surface type description to errors in the data is determined
together with its repeatability.
Three methods for comparing two surface type descriptions are presented and illustrated
for average male and average female faces. Thus a quantitative description of facial
change, or differences between individual's faces, is achieved. The possible application
of artificial intelligence techniques to automate this comparison is discussed. The
sensitivity of the description to global and local changes to the data, made by
mathematical functions, is investigated.
Examples are given of the application of this method for describing facial changes
made by facial reconstructive surgery and implications for defining a basis for facial
aesthetics using shape are discussed. It is also applied to investigate the role played by
the shape of the surface in facial recognition
Distributed Learning for Multiple Source Data
Distributed learning is the problem of inferring a function when data to be analyzed is distributed across a network of agents. Separate domains of application may largely impose different constraints on the solution, including low computational power at every location, limited underlying connectivity (e.g. no broadcasting capability) or transferability constraints related to the enormous bandwidth requirement. Thus, it is no longer possible to send data in a central node where traditionally learning algorithms are used, while new
techniques able to model and exploit locally the information on big data are necessary. Motivated by these observations, this thesis proposes new techniques able to efficiently overcome a fully centralized implementation, without requiring the presence of a coordinating node, while using only in-network communication. The focus is given on both supervised and unsupervised distributed learning procedures that, so far, have been addressed only in very specific settings only.
For instance, some of them are not actually distributed because they just split the calculation between different subsystems, others call for the presence of a fusion center collecting at each iteration data from all the agents; some others are implementable only on specific network topologies such as fully connected graphs. In the first part of this thesis, these limits have been overcome by using spectral clustering, ensemble clustering or density-based approaches for realizing a pure distributed architecture where there is no hierarchy and all agents are peer. Each agent learns only from its own dataset, while the information about the others is unknown and obtained in a decentralized way through a process of communication and collaboration among the agents. Experimental results, and theoretical properties of convergence, prove the effectiveness of these proposals. In the successive part of the thesis, the proposed contributions have been tested in several real-word distributed applications. Telemedicine and e-health applications are found to be one of the most prolific area to this end. Moreover, also the mapping of learning algorithms onto low-power hardware resources is found as an interesting area of applications in the distributed wireless networks context. Finally, a study on the generation and control of renewable energy sources is also analyzed. Overall, the algorithms presented throughout the thesis cover a wide range of possible practical applications, and trace the path to many future extensions, either as scientific research or technological transfer results
Training of Crisis Mappers and Map Production from Multi-sensor Data: Vernazza Case Study (Cinque Terre National Park, Italy)
This aim of paper is to presents the development of a multidisciplinary project carried out by the cooperation between Politecnico di Torino and ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action). The goal of the project was the training in geospatial data acquiring and processing for students attending Architecture and Engineering Courses, in order to start up a team of "volunteer mappers". Indeed, the project is aimed to document the environmental and built heritage subject to disaster; the purpose is to improve the capabilities of the actors involved in the activities connected in geospatial data collection, integration and sharing. The proposed area for testing the training activities is the Cinque Terre National Park, registered in the World Heritage List since 1997. The area was affected by flood on the 25th of October 2011. According to other international experiences, the group is expected to be active after emergencies in order to upgrade maps, using data acquired by typical geomatic methods and techniques such as terrestrial and aerial Lidar, close-range and aerial photogrammetry, topographic and GNSS instruments etc.; or by non conventional systems and instruments such us UAV, mobile mapping etc. The ultimate goal is to implement a WebGIS platform to share all the data collected with local authorities and the Civil Protectio
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A virtual environment for the modelling, simulation and manufacturing of orthopaedic devices
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The objective of this work is to investigate whether the game physics based
modelling is accurate enough to be used in modelling the motion of the human body,
in particular musculoskeletal motion. Hitherto, the implementation of game physics
in the medical field focused only on anatomical representation for education and
training purposes. Introducing gaming platforms and physics engines into
orthopaedics applications will help to overcome several difficulties encountered in
the modelling of articular joints. Implementing a physics engine (PhysX), which is mainly designed for video games, handles intensive computations in optimized ways
at an interactive speed. In this study, the capabilities of the physics engine (PhysX)
and gaming platform for modelling and simulating articular joints are evaluated.
First, a preliminary validation is carried out for mechanical systems with analytical
solutions, before constructing the musculoskeletal model to evaluate the consistency of gaming platforms. The developed musculoskeletal model deals with the human joint as an unconstrained system with 6 DOF which is not available with other joint modeller. The model articulation is driven by contact surfaces and the stiffness of surrounding tissues. A number of contributions, such as contact modelling and
muscle wrapping, have been made in this research to overcome some existing
challenges in joint modelling. Using muscle segmentation, the proposed technique
effectively handles the problem of muscle wrapping, a major concern for many; thus
the shortest path and line of action are no longer problematic. Collision behaviour
has also shown a stable response for colliding as well as resting objects, provided that it is based on the principles of surface properties and the conservation of linear and angular momentums. The precision of collision detection and response are within an acceptable tolerance controllable by varying the mesh density. An image based analysis system is developed in this thesis, mainly in order to validate the
proposed physics based modelling solution. This minimally invasive method is based
on the analysis of marker positions located at bony positions with minimal skin
movement. The image based system overcomes several challenges associated with
the currently existing methods, such as inaccuracy, complication, impracticability
and cost. The analysis part of this research has considered the elbow joint as a case
study to investigate and validate the proposed physics based model. Beside the
interactive 3D simulation, the obtained results are validated by comparing them with
the image based system developed within the current research to investigate joint
kinematics and laxity and also with published material, MJM and results from
experiments performed at the Brunel Orthopaedic Research and Learning Centre.
The proposed modelling shows the advantageous speed, reliability and flexibility of the proposed model. It is shown that the gaming platform and physics engine provide a viable solution to human musculoskeletal modelling. Finally, this thesis considers an extended implementation of the proposed platform for testing and assessing the design of custom-made implants, to enhance joint performance. The developed simulation software is expected to give indicative results as well as testing different types of prosthetic implant. Design parameterization and sensitivity analysis for geometrical features are discussed. Thus, an integrated environment is proposed to link the real-time simulation software with a manufacturing environment so as to assist the production of patient specific implants by rapid manufacturing
From standing posture to vertical jump - Experimental and model analysis of human movement
Dalla postura eretta al salto verticale - Analisi sperimentale e modellistica del movimento uman
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