8 research outputs found
Learning with Algebraic Invariances, and the Invariant Kernel Trick
When solving data analysis problems it is important to integrate prior
knowledge and/or structural invariances. This paper contributes by a novel
framework for incorporating algebraic invariance structure into kernels. In
particular, we show that algebraic properties such as sign symmetries in data,
phase independence, scaling etc. can be included easily by essentially
performing the kernel trick twice. We demonstrate the usefulness of our theory
in simulations on selected applications such as sign-invariant spectral
clustering and underdetermined ICA
Blood vessel segmentation in the analysis of retinal and diaphragm images
The segmentation and characterization of structures in medical images represents an
important part of the diagnostic and research procedures in medicine. This thesis focuses
on the characterization methods in two application fields that make use of two imaging
modalities. The first topic is the characterization of the blood vessel structure in the
human retina and the second is the characterization of diaphragm movement during
breathing. The imaged blood vessel structures are considered important landmarks in
both applications.
The framework for the retinal image processing and analysis starts with the testing
of five publicly available blood vessel segmentation methods for retinal images. The
parameters of the methods are optimized on five databases with the ground truth for
blood vessels. An approach for predicting the method parameters is proposed based on
the optimization results. The parameter prediction approach is then applied to obtain
vessel segmentation on a new database and an automatic approach to the blood vessel
classification and computation of the arteriovenous ratio is proposed and evaluated on
the new database.
The framework for the diaphragm image processing and analysis is based on the measurement
of diaphragm motion. The motion is characterized by a set of features quantifying
the amplitude and frequency of the breathing pattern, as well as a portion of the nonharmonic
movements that occur. In addition, a set of static features like the diaphragm
slope and height are proposed. Two approaches for the motion measurement are proposed
and compared. A statistical evaluation of the proposed features is performed by
comparing measurements from people with and without spinal findings.
The results from the retinal image processing and analysis revealed the possibility of the
successful prediction of the parameters of the blood vessel segmentation methods. The
automatic approach for the automatic arteriovenous ratio estimation revealed a stronger
association with blood pressure than the manually estimated ratio. The results from the
diaphragm image processing and analysis confirmed differences in the position, shape and
breathing patterns between the healthy people and people suffering from spinal findings.
The blood vessel structure was shown to be a reliable marker for characterizing the
diaphragm motion.Katedra kybernetik