Optimal scan for time-varying tomography

Pao Yue-kong Library Electronic Theses Database

Optimal scan for time-varying tomography

 

Author: Kwong, King-leong Victor
Title: Optimal scan for time-varying tomography
Degree: M.Sc.
Year: 1996
Subject: Tomography
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: v, 84, 41 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1234957
URI: http://theses.lib.polyu.edu.hk/handle/200/4702
Abstract: To eliminate the motion artifacts of a time-varying tomography is a headache issue for many scientists and engineers. The related application can be found in the clinical equipment for medical imaging. Consider a tomographic reconstruction of objects with spatially localised temporal variation, such as a thorax cross-section with a beating heart. The conventional approach is to use a linear angular sampling order, in which projections are taken progressively around the object, requires high, and sometimes infeasible scan rates to avoid motion artifacts in the reconstructed images. This may result a great demand of an expensive camera system. How to reduce the scan rate while preserving the image quality? In this dissertation, we demonstrate the use of an unconventional angular sampling order, which is described in [1] and [2] to obtain the solution. The key assumption, which allows a lower angular sampling order, is that there is no time penalty for extensive angular movement, i.e., the time delay between successive projections is independent of their angular separation. With this optimal scan technique, the sampling order can be reduced as much as four times, while the image quality is preserved. A comparison on the reconstruction results of a time-varying tomography using the Linear and Optimal Samplings will be the key content in this dissertation. The reconstruction involves the procedures of interpolation to the standard time-invariant scan format and then the filtered-back projection. The theoretical knowledge, practical designs and implementation of the two sampling schemes will be discussed which will further verify the validity of the Optimal scan for both temporally bandlimited and approximately temporally bandlimited objects.

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