Biomedical Engineering Reference
In-Depth Information
distances, speeds, and accelerations, etc. In
video compression
, this informa-
tion enables us to take advantage of the temporal redundancy in the video se-
quence; it can be used for
object tracking
[3],
image stabilization
, or cam-
era (observer) movement identification leading to
3D reconstruction
of the
scene.
segmentation
algorithms divide the image into regions according to their
speed.
Registering a pair of
stereo images
also permits the 3D reconstruction of
the scene. The spatial configuration of the cameras is known here; on the other
hand, we have to deal with occlusions. The general case of
n
cameras presents
additional challenges in maintaining the consistency.
9.1.1.1
Biomedical Applications
In the biomedical domain, there is a frequent need to compare images for analysis
and diagnostic purposes. For an efficient comparison, the images need to be
aligned. This can be accomplished by registration and subsequent warping.
Intrasubject
analysis compares images of the same subject taken at different
times in order to detect or quantify changes caused by the evolution of the
disease or the effect of the therapy.
Intersubject
analysis considers corresponding images from different sub-
jects. Aligning and combining images from many subjects leads to
atlases
, which
are annotated reference images. The individual subject images are then regis-
tered with the atlas for identification, segmentation, to detect abnormalities, and
to quantitatively characterize the shape and size of their features.
Images of the same subject with different imaging modalities can be com-
bined using
intermodality
registration to get a more complete picture of the
subject's anatomy and physiology.
Furthermore, registration helps to compensate for geometrical distortions
[4] inherent to some imaging methods, as well as for unwanted motion during
the acquisition.
9.2
Review of Registration Techniques
Most existing registration algorithms can be cast into the following general
framework:
