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OPTIMIZATIONS IN THE ASSESSMENT OF
PEDIATRIC BONE
by
David Choen Lee
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOMEDICAL ENGINEERING)
May 2009
Copyright 2009 David Choen Lee
Object Description
| Title | Optimizations in the assessment of pediatric bone |
| Author | Lee, David Choen |
| Author email | davidcle@usc.edu; davidclee@alumni.usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Biomedical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2009-02-23 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-03-11 |
| Advisor (committee chair) |
Singh, Manbir Wren, Tishya A. |
| Advisor (committee member) |
McNitt-Gray, Jill L. Gilsanz, Vicente |
| Abstract | Peripheral quantitative computed tomography (pQCT) and dual energy x-ray absorptiometry (DXA) are fundamental imaging technologies in the assessment of bone in children and adolescents. However, they may both produce misleading outcomes, particularly in growing subjects. The goal of this thesis is to quantify and minimize the shortcomings of pQCT and DXA. We have isolated factors that lead to potential errors in pQCT and DXA, offered corrections for those errors or alternative measures, and introduced an automated MRI (magnetic resonance imaging) bone feature extraction program.; A major limitation of pQCT measurements arises from scan positioning in metaphyseal density determinations. Due to a considerable gradient of cancellous bone in the region, the density reported by a conventional single slice is dependent on the location of the scan and may not come from the same exact anatomical site in different individuals or over time. As a result, interpretation of these data may be difficult. We have presented a method to measure the gradient of cancellous bone with pQCT and obtain overall measures of cancellous bone such as average density.; DXA's limitations are a product of its two-dimensional design. To derive bone measures, it assumes a homogeneous soft-tissue distribution, which leads to errors when the distribution is actually inhomogeneous. In addition, the inclusion of the vertebral posterior elements in anterior-posterior projections of the spine may misrepresent actual spine strength, which is usually associated with the vertebral body. These two factors impact DXA bone measures and may lead to recommendations that deviate from analogous outcomes from QCT (quantitative computed tomography), a three-dimensional modality. In a series of three studies, we have investigated the extent of the error due to these limitations, and attempted to reduce those errors.; Lastly, we explore the possibility of extracting bone features with MRI. Since MRI does not use ionizing radiation, it would be advantageous to use in lieu of QCT or pQCT. However, since bone suffers poor contrast in MRI, manual tracing or semi-automatic methods are usually required. To reduce operator error and improve efficiency, we have designed a fully automatic program and compared its results with established QCT methods. |
| Keyword | bone; DXA; imaging; orthopedics; pediatrics |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2018 |
| Rights | Lee, David Choen |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Lee-2588 |
| Archival file | uscthesesreloadpub_Volume51/etd-Lee-2588.pdf |
Description
| Title | Page 1 |
| Full text | OPTIMIZATIONS IN THE ASSESSMENT OF PEDIATRIC BONE by David Choen Lee A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (BIOMEDICAL ENGINEERING) May 2009 Copyright 2009 David Choen Lee |
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