Abstracts of Papers

No. 1/2: Special Issue on
**Novel Methods in Computer-Aided Biomedical Image Processing and Interpretation.
Part II**,

No. 3,

No. 4.

16 (2007) | main |

Reprints of the papers may be obtained from their authors; contact

**Editorial Office, MGV**

Institute of Computer Science

ul. Ordona 21

01-237 Warszawa, Poland`<mgv@ipipan.waw.pl>`

Special Issue Editor:Juliusz L. Kulikowski.

- Kulikowski J.L.:

**Introduction to the special issue of MG&V**.

MGV vol. 17, no. 1/2, 2008, pp. 3-4. -
Orkisz M., Flórez Valencia L., Hernández Hoyos M.:

**Models, algorithms and applications in vascular image segmentation**.

MGV vol. 17, no. 1/2, 2008, pp. 5-33. -
A synthesis of the authors' projects in the field of 3D vascular
image processing in the last decadeis provided. This work was
motivated by the following applications: display improvement,
extraction of geometrical measurements, acquisition optimization,
stent-pose planning, phantom generation, blood-flow simulations. The
methods are often dependent on the imaging modality and/or on the
anatomic region. They involve both: low-level models of intensity
patterns and profiles, and higher-level models of cylindrical
shapes. Amongst the various algorithms used, recursive tracking and
fast-marching level-sets are emphasized. Critical analysis of each
model and algorithm is carried out. Problems that remain open, and
perspectives associated with the progress of the image acquisition
techniques, are listed.

**Key words**:inertia moments, Hessian, eigen-analysis, centerlines, active contours, deformable models, generalized cylinders, simplex meshes, tracking, fast-marching level sets. -
Garcia E., Seron F., Baldassarri S.:

**The challenge of hexahedral meshing of arterial geometry**.

MGV vol. 17, no. 1/2, 2008, pp. 35-55. -
This paper describes the process of generating a hexahedral mesh
of the arterial geometry. From the finite element meshing point of
view, arterial geometry may be regarded as a volume assembly in
which every segment can be meshed separately except in the shared
surfaces. The arterial assembly is made up of three subvolumes:
arterial wall, artery lumen and atherosclerotic plaque.
A three-dimensional geometric model of each arterial segment has been
reconstructed using intravascular ultrasound images (IVUS) and
biplane angiographies. Generation of hexahedral meshes for
biological models with different physical characteristics usually
requires the use of different meshing algorithms for each region.
Vessel bifurcations have been modeled by joining the surfaces of the
reconstructed segments, using a technique based on NURBS. Therefore,
this paper describes the combination of decomposition and meshing
techniques required to meet the challenge of generating hexahedral
elements for arterial models. A variety of verification algorithms
have been used in order to calculate several algebraic quality
metrics and assess the quality of the finite element meshes generated.

**Key words**: mesh generation, hexahedra, arterial bifurcations, atherosclerosis - Jelinek H. F.:

**Automated vessel segmentation of 35mm colour non-mydriatic images in a community health screening project**.

MGV vol. 17, no. 1/2, 2008, pp. 57-68. -
Proliferative diabetic retinopathy is a complication of diabetes that can eventually
lead to blindness. Early identification of this complication reduces the risk
of blindness so that timely treatment can be initiated. In rural and remote
regions, widespread population screening is practically impossible due
to the lack of ophthalmologists and the cost associated with rural visits
by specialists. Several methods for vessel segmentation have been discussed
in the literature, but none have used non-mydriatic colour images obtained
from community screening initiatives. Rural screening clinics currently use
either 35mm or Polaroid photography. In addition, the quality of the images
is often much lower. Scanning images at 300dpi provides very low resolution
images which combined with the low quality requires a robust algorithm
to identify vessels with high accuracy. Visual inspection by an ophthalmologist
judged 46 images (88%) to represent an acceptable level of segmentation.
Despite the low resolution and quality of images, the Gabor wavelet provided
vessel segmentation results that were usable in rural community screening
projects and in some cases identified vessels obscured by haemorrhages
better than the expert observer.

**Key words**: vessel segmentation, wavelet transform, non-mydriatic, diabetic retinopathy. -
Goszczynska H.:

**A method for densitometric analysis of moving object tracking in medical images**.

MGV vol. 17, no. 1/2, 2008, pp. 69-90. -
The aim of this work is to develop a method of automatic data
collection for coronary blood flow estimation based on computer
analysis of angiographic image sequences. In the methods of coronary
flow measurements, apart from problems involving densitometric
analysis, there is also the problem of cyclic movement of the
measurement field, i.e. of an artery segment or part of the
myocardium. The system of automatic artery segment tracking
presented in this paper does not only reduce the "manual effort" of
the operator to establish the region of interest in the frame
sequence, but also makes it possible to plot a densitometric curve
with the time resolution equal to that of the frame sequence. The
algorithm thus implemented, based on a template matching method,
makes it also possible to trace the results of automatic detection
of some characteristic points within the structure of arteries and
to correct any faulty matching. The incorporation of the movement
trajectories obtained allows us to trace the movement of the part of
the myocardium close to the characteristic points of the artery with
the aim of estimating the degree of myocardium perfusion. This
relatively simple algorithm is acceptable for routine clinical
testing due to the short time of frame sequence analysis (few
minutes) and its relatively small error (the maximum estimated error
of the automatic analysis is less than 11%). The comparative
analysis of the results obtained for the template matching algorithm
based on several criteria of similarity failed to establish any
specific criterion with regard to acceleration or matching accuracy.

**Key words**: moving object tracking, similarity measures, image registration, densitometric measurements. - Cha S.-H., Gargano M. L., Chang S., Quintas L. V., Wahl E. M.:

**Estimating a vascular network growth using random graphs**.

MGV vol. 17, no. 1/2, 2008, pp. 91-103. -
Vascular networks develop by way of angiogenesis, a growth process
that involves the biological mechanisms of vessel sprouting
(budding) and splitting (intussusception). Graph theory is
excellently suited to model vascular networks and to analyze their
properties (invariants). In particular, a random graph process model
can simulate the development of a vascular network that has been
modeled using graph theory. The renal glomerulus is one example of
such a vascular network. Here the correlation between the invariants
of this vascular network modeled as a graph and the mechanisms of
the network growth using a random graph process are studied. It is
proposed that the relative frequencies of sprouting and splitting
during the growth of a given renal glomerulus can be estimated by
the invariants (root distance, radius, and diameter) of the graph
representing the renal glomerulus network. Experimental evidence has
been given to support this conjecture.

**Key words**: Renal glomerular network, random graph process, graph invariants, pattern matching. - Klette G.:

**Skeletal curves of 3D astrocyte samples**.

MGV vol. 17, no. 1/2, 2008, pp. 105-129. -
The paper discusses the concept of simple (and non-simple)
elements for the generation of topologic skeletons, their
transformation into abstract curve graphs, and the analysis of such
graphs.

The definition of a branching index of a point on a curve is fundamental in curve theory (in Euclidean space), and leads to important subjects of curve analysis. This paper derives analogous notions, such as branching index, branch element, and junction, for digital curves, which allow us to introduce new concepts for analyzing complex digital curves in a 3D space. The paper provides new theoretical insights, and also discusses an application project (the description of astrocytes in 3D confocal images of human brain tissue).

This work was originally initiated by a particular research project at the Medical School of The University of Auckland. Medical experts developed the hypothesis that features of astrocytes in confocal volume scans are useful for defining states between normal and abnormal tissue. The calculation of skeletal curves, as proposed and studied in this paper, provides a valuable tool for calculating such features.

**Key words**: shape analysis, skeletonization, thinning, astrocytes. - Pietka B. D., Dulewicz A., Jaszczak P.:

**Removing artefacts from microscopic images of cytological smears**.

MGV vol. 17, no. 1/2, 2008, pp. 131-152. -
This paper gives an overview of authors' attempts to design a
computer-assisted urine smear screening system, focusing on the
nastiest issues hampering its successful practical implementation.
There are many valuable works concerning more or less sophisticated
image processing and data mining algorithms which are capable of
automatically detecting pathological morphology of cytological
objects and distinguishing them from normal ones. Unfortunately,
most of the attempts to implement those smart ideas in real world
are likely to fail because of one but fundamental obstacle --
artefacts. If not properly identified and removed from the
analysis, they tend to generate so many false-positive warnings that
the automated support is going to be useless because of its
dramatically low specificity. Our paper addresses this neglected
problem, trying to point out some general rules and implementation
details that should be followed to reduce the influence of artefacts
on overall system performance.

**Key words**: computer-aided digital cytology, urologic oncology, microscopic smears screening systems, urinary bladder cancer. - Marciniak A., Nieczkowski T., Obuchowicz A.:

**Color homogram for segmentation of fine needle biopsy images**.

MGV vol. 17, no. 1/2, 2008, pp. 153-165. -
In this paper, a new weighted clustering algorithm for image
segmentation in cytopathology is introduced. The weights
incorporating spatial information into pixel-based segmentation are
computed with use of a color homogram. The effectiveness of the
proposed solution is evaluated on microscopic fine needle biopsy
(FNB) images. The results of the classical fuzzy c-means algorithm
and its weighted modification are compared.

**Key words**: homogeneity, color image segmentation, clustering, fine needle biopsy, fuzzy logic. - Witkowski L.:

**A computer system for sperm cells motility evaluation**.

MGV vol. 17, no. 1/2, 2008, pp. 167-186. -
The article describes the first module of a computer system for
human sperm assessment. Different image acquisition methods were
described and optical microscope with bright optic was selected as
the most appropriate one. Image enhancement and processing methods
were selected and customized to achieve effective sperm cells
recognition and tracking. Trajectories of sperm cells and their
movement parameters were found, calculated and classified in
compliance with WHO standards.

**Key words**: image processing, image recognition, sequence of images, microscopy techniques, WHO. - Ramoser H.:

**Leukocyte segmentation and SVM classification in blood smear images**.

MGV vol. 17, no. 1/2, 2008, pp. 187-200. -
Automated leukocyte detection, segmentation, and classification is
an important task in clinical diagnosis. In this paper we present an
approach to leukocyte cytoplasm and nucleus segmentation that is
robust with respect to image quality and cell appearance. Cell
properties are described by a set of statistical color and shape
features. Pairwise coupling of SVM classification results is used to
determine cell type probabilities. Evaluation of the method on a set
of 1166 images containing 13 different cell types has resulted in
95% correctly segmented cells and a classification accuracy of 88%
(at 20% reject rate).

**Key words**: cytometry, feature extraction, multiclass SVM. - Koprowski R., Wrobel Z.:

**Analysis of the inclination of elongated biological objects - microtubules**.

MGV vol. 17, no. 1/2, 2008, pp. 201-215. -
In the paper we propose a new method for determining the
inclination angle of microtubules. The method allows us to obtaining
an angular inclination histogram, taking into account the area of
microtubules rather than their number only. We present two kinds of
microtubule approximation: global and local one. In the global approach
microtubules are approximated with one or more straight lines,
whereas the local approach defines a direction field for each pixel.

**Key words**: microtubules, geometric approximation, field of direction, inclination.

- Bojar K., Nieniewski M.:

**Analysis of temporal variations of dynamic textures by means of the SGLDM with application to EIT solar images**.

MGV vol. 17, no. 3, 2008, pp. 219-247. -
The paper discusses applicability of texture analysis methods to
Extreme-Ultraviolet Imaging Telescope (EIT) images obtained from the
SOHO mission, and in particular analyses of the solar texture by
means of the Spatial Gray Level Dependence Matrices (SGLDMs). Based
on the observations, a theoretical parametric model is proposed for
the SGLDM. Subsequently, the Haralick features are computed directly
for the time sequence of preprocessed images, as well as and for the
proposed model of the SGLDM. Time evolution of model parameters as
well as measures of goodness fit of the model to image data for the
period of one year is presented. The results obtained confirm the
correctness of the model. In view of the simplicity of the model,
it gives remarkably good results. A new method for solar limb
extraction is described in the Appendix. The method is superior to
those presented in the literature since it uses no external
parameters, such as thresholds.

**Key words**: texture analysis, texture modelling, SGLDM, solar images, EIT images. - Rodríguez T.:

**Shadow removal for robust vehicle detection**.

MGV vol. 17, no. 3, 2008, pp. 249-266. -
Shadow removal is a critical process for any computer vision based
vehicle detection system. Traditional shadow removal methods are not
sufficiently robust since they frequently remove parts of the
vehicles together with the shadows. For robust shadow identification
and removal, shadow information must be compiled at every step of
the computer vision chain from the time the shadow enters the scene
until it finally disappears. In this paper we present a shadow
removal algorithm that preserves the compactness of the vehicles'
object masks while allowing for dealing with changing illumination
conditions, long and broken shadows and multiple shadows at night.
The method is based on a complex shadow model which includes, among
others, information regarding: luminance and chromaticity,
morphology, dynamics and spatial relations analysis.

**Key words**: computer vision, real-time, traffic monitoring, shadow removal. - Rozen T., Boryczko K., Alda W.:

**A GPU-based method for approximate real-time fluid flow simulation**.

MGV vol. 17, no. 3, 2008, pp. 267-278. -
Fluid flow can be realistically simulated by physical models. We
present a method for simplifying the Navier-Stokes equations by
relaxing the incompressibility constraint. Our method allows for
low-cost real-time simulation of two-dimensional fluid flow with
accuracy sufficient for computer graphics. The implementation takes
advantage of recent programmable floating-point graphics hardware,
which performs all the necessary computations.

**Key words**: fluid dynamics, graphics hardware, physically-based simulation, pseudo-compressibility method. - Korohoda P., Dabrowski A.:

**Generalized convolution for extraction of image features in the primary domain**.

MGV vol. 17, no. 3, 2008, pp. 279-297. -
In this paper, a class of techniques for flexible extraction of image features is proposed. These techniques are based on the convolution type filtering in the primary domain. The mentioned flexibility results from the fact that any discrete transform suitable for the analysis of desired image features (as, e.g., the Karhunen-Loeve transform) may be designed and the filter with the assumed transform-domain properties may be applied straightforwardly in the image (i.e., primary) domain. The proposed solution creates an entirely new approach to image filtering. After recalling the concept referred to by the authors as generalized convolution and extending it to the 2-dimensional case, the theoretical results are illustrated with several examples based on filtering of the test image with filters designed in the Haar, Hadamard and the DCT II domains. Finally, it is explained how the proposed approach indicates several possible ways for further developments towards the design of image-and-feature based tools.

**Key words**: generalized convolution, discrete transforms, image decomposition, image filtering. - Hati S.:

**Estimation of pose parameters from a set of least square objective functions**.

MGV vol. 17, no. 3, 2008, pp. 299-312. -
In this paper, we have attempted to solve the pose estimation
problem for a 3-dimensional object by independently estimating the
pose parameters through the minimization of a set of objective,
functions, using Gauss approximation techniques for least squares
optimization. In our implementation, the 3-D object is assumed to
have three degrees of freedom on a flat surface, which is typical of
automated visual inspection applications. However, the solution can
be also extended to greater degrees of freedom. We have is shown
that the pose can be estimated by only considering the x-coordinates
of the known vertices in the projected space, but the same is not
true if we consider the
*y*-coordinates alone. We propose a set of modified objective functions from which it is possible to find the pose parameters. The parameters have been determined in noisy conditions under*20-dB*and*40-dB*SNR values and the robustness of the estimators is confirmed.

**Key words**: pose estimation, camera calibration, least square estimation, robust estimator. - Zhang Y., Sung E.:

**EDFCES: A new example-driven 3D face construction and editing system**.

MGV vol. 17, no. 3, 2008, pp. 313-346. -
This paper presents an automatic runtime system for generating
varied, realistic face models by synthesizing a global face shape
and local facial features according to intuitive, high-level control
parameters. Our method takes as examples 3D face scans in order to
exploit the parameter-to-geometry correlations present in real
faces. In order to establish the correspondences among the scanned
models, we use a three-step model fitting approach to conform a
generic head mesh onto each scanned model. We transform the obtained
data sets of global face shapes and local feature shapes into vector
space representations by applying a principal component analysis
(PCA). We compute a set of face anthropometric measurements to
parameterize the exemplary shapes in the measurement spaces. Using
PCA coefficients as a compact shape representation, we approach the
shape synthesis problem by forming scattered data interpolation
functions designed to generate the desired face shape by taking
anthropometric parameters as input. At runtime, the interpolation
functions are evaluated for the input parameter values to produce
new face geometries at an interactive rate. The correspondence among
all exemplary face textures is obtained by parameterizing the 3D
generic mesh over a 2D image domain. The new feature texture with
the desired attributes is synthesized by interpolating the example
textures. The resulting system is intuitive to control and
fine-grained. We demonstrate our method by applying different
parameters to generate a wide range of face models.

**Key words**: face modeling, facial features, anthropometry, interpolation, PCA, model fitting, 3D scanned data.

16 (2007) | main |