- Visual Planning and Verification of Deep Brain Stimulation Interventions
Student: Elhassan M. Abdou
Supervisor: Timo Ropinski, Dept. of Science and Technology, Linköping University
Reviewer: Robin Strand
Publisher: CBA Master Thesis No. 125 / IT nr 11 090
Abstract: Deep Brain Stimulation (DBS) has resulted in a
renaissance as an alternative way for treatment of Parkinson's
disease and essential tremor. Deep brain stimulation employ the use
of high electric field to stimulate some brain centers. The electric
field in the brain is generated from chronic implanted electrodes in
the brain. The final position of the electrodes in the brain is
specified by the aid of CT and MR scans for the patient's head
before and after the operation. A study of electric field
distribution in the brain is required to interpret and improve the
action of DBS. In this master thesis project, Voreen was extended to
visualize a multimodal volume of the CT and MR images. The MR volume
was segmented to extract the brain from the skull in T1 weighted
images. Some image processing techniques were developed to enhance
the contrast of CT and MR images. In order to stimulate electric
field in the brain, the neurologists are allowed to design and
position the electrodes in the reconstructed volume. The electrodes
and some pre-modeled electric fields can be visualized in the
reconstructed volume and the slice views. A mesh generator was
developed using delaunay tetrahedralization. The generated mesh can
be sent to PDE solver to solve Laplace equation describing the
distribution of electric field.
- Digital Distance Functions Defined by Sequence of Weights
Student: Alexander Denev
Supervisor: Robin Strand
Reviewer: Gunilla Borgefors
Publisher: CBA Master Thesis No. 126 / IT nr 11 082
Abstract: In this paper, digital distance functions using
sequences of weights are studied and used to approximate the
Euclidian distance. Sequences of weights that guarantee a low
maximum absolute error for path lengths of up to 10000 are
calculated. A necessary condition and a sufficient condition for
metricity of this kind of distance function are established.
- Efficient Implementation of Polyline Simplification for Large Datasets and Usability Evaluation
Student: Sadan Ekdemir
Supervisor: Jörn Letnes
Reviewer: Stefan Seipel
Publisher: CBA Master Thesis No. 127 / IT nr 11 069
Abstract: An in-depth analysis and survey of polyline
simplification routines is performed within the project. The
research is conducted using different simplification routines and
performing evaluative tests on the outputs of each simplification
routine. The project lies in between two major fields, namely
Computer Graphics and Cartography, combining the needs of both sides
and uses the algorithms that are developed for each field. After the
implementation of the algorithms, a scientific survey is performed
by comparing them according to the evaluation benchmarks, which are
performance, reduction rate and visual similarity. Apart from the
existing routines, one new simplification routine, triangular
routine is developed and recursive Douglas-Peucker routine is
converted into non-recursive. As a preprocessing part, Gaussian
smoothing kernel is used to reduce noise and complexity of the
polyline, and better performances are achieved. The end of research
shows that there is no best model instead there are advantages and
disadvantages of each simplification routine, depending on the prior
need. It is also shown that usage of Gaussian smoothing as a
filtering process improves the performance of each simplification
routine.
- Image Analysis on Wood Fiber Cross-Section Images
Student: Sitao Feng
Supervisor: Bettina Selig
Reviewer: Cris Luengo
Publisher: CBA Master Thesis No. 128 / IT nr 11 028
Abstract: Lignification of wood fibers has a significant
impact on wood properties. To measure the distribution of lignin in
compression wood fiber cross-section images, a crisp segmentation
method had been developed. It segments the lumen, the normally
lignified cell wall and the highly lignified cell wall of each
fiber. In order to refine this given segmentation the following two
fuzzy segmentation methods were evaluated in this thesis: Iterative
Relative Multi Objects Fuzzy Connectedness and Weighted Distance
Transform on Curved Space. The crisp segmentation is used for the
multi-seed selection.
The crisp and the two fuzzy segmentations are then evaluated by
comparing with the manual segmentation. It shows that Iterative
Relative Multi Objects Fuzzy Connectedness has the best performance
on segmenting the lumen, whereas Weighted Distance Transform on
Curved Space outperforms the two other methods regarding the
normally lignified cell wall and the highly lignified cell wall.
- Audio Editing in the Time-Frequency Domain Using the Gabor Wavelet Transform
Student: Ulf Hammarqvist
Supervisor: Erik Wernersson
Reviewer: Anders Brun
Publisher: CBA Master Thesis No. 129 / UPTEC F nr F 11 022
Abstract: Visualization, processing and editing of audio,
directly on a time-frequency surface, is the scope of this
thesis. More precisely the scalogram produced by a Gabor Wavelet
transform is used, which is a powerful alternative to traditional
techinques where the wave form is the main visual aid and editting
is performed by parametric filters. Reconstruction properties,
scalogram design and enhancements as well audio manipulation
algorithms are investigated for this audio representation. The
scalogram is designed to allow a flexible choice of time-frequency
ratio, while maintaining high quality reconstruction. For this mean,
the Loglet is used, which is observed to be the most suitable filter
choice. Re-assignmentare tested, and a novel weighting function
using partial derivatives of phase is proposed. An audio
interpolation procedure is developed and shown to perform well in
listening tests.The feasibility to use the transform coefficients
directly for various purposes is investigated. It is concluded that
Pitch shifts are hard to describe in the framework while noise
thresh holding works well. A downsampling scheme is suggested that
saves on operations and memory consumption as well as it speeds up
real world implementations significantly. Finally, a Scalogram
``compression'' procedure is developed, allowing the caching of an
approximate scalogram.
- Enriching Circuit Switched Mobile Phone Calls with Cooperative Web Applications
Student: Måns Hommerberg
Supervisor: Johan Kristiansson
Reviewer: Olle Eriksson
Publisher: UPTEC F nr 11051
Abstract: The thesis investigates the possibility to enrich
standard mobile phone calls with cooperative web
applications. Originating from the research field know as Computer
Supported Cooperative Work (CSCW) this thesis report introduces and
describes the implementation of several applications which can be
used by the calling parties together during a phone
call. Additionally, the report describes a proof-of-concept
prototype for the Android platform, and discusses the performance of
cooperative web application running on mobile devices in terms of
network and CPU use.
The conclusions of the thesis describe a prototype application
addressing and implementing the requirements as described by the
theory of computer supported collaborated work. The performance of
the running application showed to be satisfactory, both regarding to
network demand and processor use.
- Registration of 3D Volumetric CT Images
Student: Shuo Li
Supervisor: Erik Wernersson
Reviewer: Anders Brun
Publisher: CBA Master Thesis No. 130 / IT nr 11 080
Abstract: This master thesis aims to develop a system for
analyzing transformation between two volumetric CT images. The
volumetric image data we process is taken from a composite
material. This composite material combines wood fibre and plastic
and can be used to make for instance hockey sticks or
furniture. Because of the wood fibre embedded in this composite
material, it absorbs water and sometimes deforms. By observing
volumetric images generated by micro computed tomography (micro-CT),
we know that the organization of fibre embedded in this material is
very complicated. This makes it difficult to predict the deformation
on beforehand. In our study, we have seen rigid transformations,
non-rigid transformations and even discontinuities transformations
(cracks). For a pair of very small sub volumes, in dry and wet
condition, we have found that the transformation can approximated by
a rigid transformation combined with a scaling value. To find this
transformation, our system includes two key phases. In the first
phase, we extract feature points in dry and wet condition. In the
second phase, we register the feature points derived from dry and
wet condition. In the feature point extraction phase, we have
adapted different methods, for instance the Scale- Invariant Feature
Transform (SIFT) method is used to extract features. In the
registration phase, we have tested three different registration
algorithms. The first algorithm is based on concepts from Random
Sample Consensus (RANSAC). The second algorithm is inspired from the
Iterative Closest Point (ICP) method. The third method is a novel
algorithm that we call Spatial Invariant Registration. In the
report, we compare the different methods in the feature extraction
phase and in the registration phase. Finally, we discuss how our
system can be extended to give better results with better accuracy.
- Evaluation of a Model-free Approach to Object Manipulation in Robotics
Student: Guoliang Luo
Supervisors: Danica Kragic, Carl-Henric Ek, Royal Institute of Technology
Reviewer: Anders Brun
Publisher: CBA Master Thesis No. 131 / IT nr 11 035
Abstract: Action Recognition is crucial for object
manipulation in robotics. In recent years, Programming by
Demonstration has been proposed as a way for a robot learning tasks
from human demonstrations. Based on this concept, a model-free
approach for object manipulation has recently been proposed in
[1]. In this thesis, this model-free approach is evaluated for
Action Recognition. In specific, the approach classifies actions by
observing object-interaction changes from video.
Image segmentation to videos presents various difficulties, such as
motion blur, complex environment, Over- and Under-
segmentation. This thesis investigates and simulates these image
segmentation errors in a controllable manner. Based on the
simulation, two different similarity measure methods are evaluated:
The Substring Match (SSM) and Bhattacharyya Distance (B-Distance)
method. The results show that the B-Distance method is more
consistent and capable to classify actions with higher noise level
compare to the SSM method.
Further, we propose an action representation using kernel
method. The evaluation shows that the novel representation improves
Action Recognition rate significantly.
- Rendering Software for Multiple Projectors
Student: Fredrik Nysjö
Supervisor: Robin Strand
Reviewer: Ingrid Carlbom
Publisher: CBA Master Thesis No. 132 / IT nr 11 081
Abstract: CBA is currently developing a haptic glove that will be integrated with a
new type of 3D holographic display. A prototype of this display has
been developed at the Royal Institute of Technology and consists of
standard off-the-shelf projectors and a special holographic optical
element. The latter acts as a projection screen that creates a
narrow viewing slit for each projector's image; this allows for
autostereoscopic viewing from more than one viewing angle. The
rendering software for the display prototype at the Centre for Image
Analysis can render a fixed number of static perspective views of
virtual 3D scenes. But the software's rendering pipeline was not
properly calibrated for the intended application of the display:
co-located haptics. Thus, the views are rendered without proper
off-axis projection matrices, and they also exhibit keystone
distortion from oblique projector angles when they are projected on
the holographic optical element. In this master's thesis work, we
develop a software library that extends the existing rendering
software with support for keystone correction and arbitrary off-axis
projections. We use this library to calibrate the rendering pipeline
and the display. We also develop software tools that facilitate the
calibration task. Furthermore, when views are rendered with static
perspective, a viewer perceives a discrete transition between two
distinct perspectives whenever he or she moves an eye from one
viewing slit to an adjacent slit. To make these view transitions
smooth and reduce other types of perspective errors, we couple the
display with an optical tracking system for head-tracking and
experiment with adding dynamic perspective to the display. We
conclude that while the addition of dynamic perspective helps reduce
perspective errors, the display would need narrower viewing slits in
order to allow smooth view transitions.
- Orbit Segmentation for Cranio-Maxillofacial Surgery Planning
Student: Johan Nysjö
Supervisor: Ingela Nyström
Reviewer: Ewert Bengtsson
Publisher: CBA Master Thesis No. 124 / IT nr 11 010
Abstract: A central problem in cranio-maxillofacial (CMF)
surgery is to restore the normal anatomy of the facial skeleton
after defects, e.g., malformations, tumours, and trauma to the
face. There is ample evidence that careful pre-operative surgery
planning can significantly improve the precision and predictability
of CMF surgery as well as reduce the post-operative morbidity. In
addition, the time in the operating room can be reduced and thereby
also costs. Of particular interest in CMF surgery planning is to
measure the shape and volume of the orbit (eye socket), comparing an
intact side with an injured side. These properties can be measured
in 3D CT images of the skull, but in order to do this, we first need
to separate the orbit from the rest of the image - a process called
segmentation.
Today, orbit segmentation is usually performed by experts in CMF
surgery planning who manually trace the orbit boundaries in a large
number of CT image slices. This manual segmentation method is
accurate but time-consuming, tedious, and sensitive to operator
errors. Fully automatic orbit segmentation, on the other hand, is
unreliable and difficult to achieve, mainly because of the high
shape variability of the orbit, the thin nature of the orbital
walls, the lack of an exact definition of the orbital opening, and
the presence of CT imaging artifacts such as noise and the partial
volume effect.
The outcome of this master's thesis project is a prototype of a
semi-automatic system for segmenting orbits in CT images. The system
first extracts the boundaries of the orbital bone structures and
then segments the orbit by fitting an interactive deformable simplex
mesh to the extracted boundaries. A graphical user interface with
volume visualization tools and haptic feedback allows the user to
explore the input CT image, define anatomical landmarks, and guide
the deformable simplex mesh through the segmentation.
To evaluate the performance of our segmentation system, we let three
test users independently segment 14 orbits twice (in a set of seven
CT images) with the segmentation tools provided by the system. In
order to assess segmentation accuracy, we construct crisp and fuzzy
ground truth segmentations from manual orbit segmentations performed
by the three test users. The results of this case study indicate
that our segmentation system can be used to obtain fast and accurate
orbit segmentations, with high intra-operator and inter-operator
precision.
- Scalable Web Application using Node.JS and CouchDB
Student: Umesh Paudyal
Supervisor: Claudijo Borovic
Reviewer: Olle Eriksson
Publisher: IT nr 11 066
Abstract: This report presents design and implementation of a
protoype application using server side javascript programming
language, node.JS and couchDB as backend database. It scales and
evaluates the developed prototype application and the couchDB for
their scalability and performance.
The report concludes that node.JS is a suitable framework for
development of scalable web servers and couchDB as a backend
database, though natively not distributed and scalable, can be
scaled and distributed across multiple nodes using clustering and
replication mechanism.
- Mobile Application Development for Android - Solving Complex Debt Situations
Students: Alexander Sjöberg and Emil Larsson
Supervisor: Tom Smedsaas
Reviewer: Olle Eriksson
Publisher: TVE nr 11 007
Abstract: The goal of the project has been to develop an
Android application whose function is to calculate the necessary
transactions, minimized in number, to resolve a complex debt
situation within a group of individuals. These types of situations
frequently occur in everyday life, for example when a group of
friends cook dinner together and different people pay for various
expenses such as food and beverages. The work resulted in the
application SplitIt, a stylish and easy-to-use application that
meets the desired specifications. Uncertainties exist however,
whether the algorithm thatcalculates the transactions is optimized
regarding the minimum number oftransactions required. Some measures
should be taken before the product is launched on the Android
Market. The development of icons, for example, has been put to the
side with the intention to spend more time on other parts of the
user interface and algorithm development. Splitit has been developed
by studying similar applications on the Android Market and by
carefully considering usability. Before starting the implementation
of the application, a user study was conducted in which sketches of
the proposed user interface was designed and a test panel had the
opportunity to navigate through the application. The study clarified
unclear as well as appealing parts of the user interface.
- Image Analysis for Grain Quality Assessment
Student: Fraz Ali
Supervisor: Jaan Luup, Maxx automation AB
Revierer: Cris Luengo
Publisher: IT nr 11 004 (confidential report)
Abstract: Assessing grain quality is a critical task to ensure that the grain-based products meet the food industry standards. Due to the complex texture-based symptoms, this process is carried out manually by quality assurance staff. To overcome the expense and inconsistencies of the process, an automated solution for grain quality is desirable.
For decades, researchers have been trying to improve the automated analysis of grains, and many image-based solutions for grain sorting have been proposed. However, none of these solutions is reliable and fast enough. Hence, the grain quality assessment is still performed manually. Recent advancement in computer vision systems and rapid progress in computer hardware industry demands that new efforts should be made to automate the complex task of grain quality assessment.
To develop an image-based solution for grain quality requires deep understanding of the symptoms as well as efficient image analysis techniques, to meet both the accuracy and performance requirements.
The purpose of this thesis is to investigate and develop efficient image analysis algorithms for grain quality assessment. An existing grain sorting system is used to acquire images. A set of image-based solutions is developed. In most of the algorithms high accuracy is achieved. A machine based on these solutions will be developed in future.
