UNaliasing quasi-Periodic signals exploiting inter-period correlation Associated through unpaCKing(UNPACK)
Date Issued
2007
Date
2007
Author(s)
Hsu, Jia-Shuo
DOI
en-US
Abstract
This thesis concerns a modified dynamic cardiac imaging and reconstruction
technique (referred to as UNPACK throughout the thesis)that acquires and
reconstructs the undersampled dynamic images exploiting inter-period cor-
relations of quasi-periodic signals. Dynamic images of moving objects often
exhibit significant correlation in their k-spaces and time, enabling improved
temporal resolution through accelerated sampling of the dynamic object by
acquiring undersampled images at the cost of aggravated aliasing. Developed
methods such as UNFOLD and k-t BLAST de-alias these images by exploit-
ing their spatiotemporal correlation, yet with inherent limitations inducing
loss of phases and increased reconstruction error in high frequency compo-
nents. Our work shows that by altering the conventional N-dimensional
quasi-periodic representation into a N + 1 dimensional representation ac-
cording to its periodicity, it is possible to obtain lower overall variances and
higher reconstruction accuracy of high frequency components accompany-
ing enhanced recovery of dynamics. It also demonstrates extra flexibility of
bandwidth usage yet higher susceptibility to displacement, which can both
be explained by mapping a portion of the targeting problems sphere-packing
problem. This formulation shows that the modified formalism proposed in
UNPACK facilitates the exploitation of intrinsic correlation in quasi-periodic
signals. However, these improvements are achieved at the cost of increased
susceptibility toward displacement as in previous methods. By implement-
ing UNPACK on dynamic cardiac images, we are able to obtain images with
improved dynamics and higher accuracy at systolic phases in comparison
to those reconstructed with k-t BLAST. These results are consistent with
our previous assumptions concerning improved high frequency performances.
Therefore, it is possible to further recover the dynamics of dynamic cardiac
images by exploit their inherent inter-period correlations.
Subjects
動態影像
UNFOLD
k-t BLAST
心臟
週期間關連性
疏取樣
dynamic imaging
cardiac
inter-period correlation
undersampling
Type
thesis
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