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Access Type

WSU Access

Date of Award

January 2018

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biomedical Engineering

First Advisor

E. Mark Haacke

Abstract

BLOOD OXYGENATION QUANTIFICATION IN THE HUMAN FETAL BRAIN USING SUSCEPTIBILITY WEIGHTED IMAGING AND MAPPING

by

BRIJESH KUMAR YADAV

May 2018

Advisor: Dr. E. Mark Haacke

Major: Biomedical Engineering with Dual title in Biomedical Imaging

Degree: Doctor of Philosophy

Oxygen is a source of life for us and our dependency upon it begins in the fetal stage. Normal growth and development of the fetus rely on the adequate supply of oxygen. Therefore, placenta undergoes morphological and functional changes throughout pregnancy to accommodate the oxidative needs of the growing fetus. However, obstruction to this supply might lead to fetal hypoxia or manifest intrauterine growth restriction (IUGR) which in turn, causes physical and neurological deficits. A combination of fetal assessment tests, including ultrasound-based blood flow indices from feto-placental circulation are used today for identifying hypoxic fetuses antenatally. Despite this, only about 15% to 25% of those cases are detected. Moreover, there are no non-invasive methods clinically present for measuring fetal brain oxygenation across second and third trimester. Because of this, normal cerebral blood oxygenation levels of the growing human fetus are not known.

In this work, therefore, we aimed to fill this knowledge gap by evaluating the fetal brain oxygenation using a magnetic resonance imaging (MRI) based technique called as susceptibility weighted imaging (SWI). Using the intravascular phase information of the superior sagittal sinus (SSS), venous oxygenation in the fetal brain was measured and the baseline fetal oxygenation was established. We also presented a multi-modality approach to study the significance of correlating the brain perfusion using measured Ultrasound (US) with cerebral oxygenation measured using SWI in the healthy human fetuses. Finally, we explored the feasibility of applying a model and orientation independent method named as quantitative susceptibility mapping (QSM) for more robust fetal blood oximetry. These efforts will in-part have helped in paving the way for a non-invasive technique for assessing fetal health and could have significant impact in early detection of hypoxic fetuses in high-risk pregnancies.

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