MPhil Thesis Defence


"Non-Rigid Image Registration on Brain Magnetic Resonance Images
Using Graph-Cuts"

By

Mr. Wai-Ho Tang


Abstract

We present a graph-cuts based method for non-rigid medical image
registration on brain magnetic resonance images. In this thesis, the
non-rigid image registration problem is reformulated as a discrete
labelling problem. According to a voxel-to-voxel similarity measure, each
voxel in the source image is assigned a displacement label, which
represents a displacement vector, indicating which position in the
floating image it is spatially corresponding to. A smoothness constraint
based on the first derivative is used to penalize sharp changes in the
displacement labels across voxels. The image registration problem is
therefore modeled by two energy terms based on intensity similarity and
smoothness of the displacement field. These energy terms are submodular
and can be optimized by using the graph-cuts method via alpha-expansions,
which is a powerful combinatorial optimization tool and capable of
yielding either a global minimum or a local minimum in a strong sense.
Using the realistic brain phantoms obtained from the Simulated Brain
Database, we have compared the registration results of the proposed method
with the two state-of-the-art image registration approaches: the free-form
deformation based method and the demons based method. It is found that the
proposed method is more robust to different challenging non-rigid
registration cases with consistently higher registration accuracy than
those two methods, and gives realistic recovered deformation fields.


Date:				Wednesday, 22 August 2007

Time:				2:00p.m.-4:00p.m.

Venue:				Room 3416
				Lifts 17-18

Committee Members:		Dr. Albert Chung (Supervisor)
				Dr. Dit-Yan Yeung (Chairperson)
				Dr. Huamin Qu


**** ALL are Welcome ****