Multichannel Methods for Restoration in Computed Imaging

This dissertation addresses data-driven image restoration for computed imaging systems. The work is focused on problems in two imaging modalities: the autofocus problem in synthetic aperture radar (SAR), and the problem of estimating coil sensitivities in parallel magnetic resonance imaging (PMRI). A common thread in both problems is their inherent multichannel nature, i.e., both exhibit special structure due to the redundancy provided by multiple signal measurements. By explicitly exploiting the multichannel structure, novel algorithms are developed offering improved restoration performance. We first present a theoretical study providing more insight into metric-based SAR autofocus techniques. Our analytical results show how metric-based methods implicitly rely on the multichannel defocusing model of SAR autofocus to form well-focused restorations. Utilizing the multichannel structure of the SAR autofocus problem explicitly, we develop a new noniterative restoration approach termed the MultiChannel Autofocus (MCA) algorithm. In this approach, the focused image is directly recovered using a linear algebraic formulation. Experimental results using actual and simulated SAR data demonstrate that MCA provides superior performance in comparison with existing autofocus methods. Lastly, we develop a new subspace-based approach for estimating receiver coil sensitivity functions used in PMRI reconstruction. Our approach does not rely on sum-of-squares assumptions used in previous PMRI techniques, thus avoiding potential problems such as poor image contrast and aliasing artifacts.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Morrison, Robert Lee, Jr

Contributors dc:contributor

• Do, Minh N.

• Engineering, Electronics and Electrical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3269986

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/81016