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Title page for ETD etd-03252016-155151


Type of Document Dissertation
Author Gifford, Aliya
URN etd-03252016-155151
Title MRI characterization of brown adipose tissue in adult humans with validation by PET-CT
Degree PhD
Department Chemical and Physical Biology
Advisory Committee
Advisor Name Title
E. Brian Welch Committee Chair
Malcolm J. Avison Committee Co-Chair
Alan D. Cherrington Committee Member
Bruce M. Damon Committee Member
Seth A. Smith Committee Member
Keywords
  • computed tomography
  • positron emission tomography
  • white adipose tissue
  • brown adipose tissue
  • fat signal fraction
  • fat water magnetic resonance imaging
  • tissue segmentation
  • tissue classification techniques
  • image processing
Date of Defense 2015-12-09
Availability restricted
Abstract
Brown adipose tissue (BAT) known to function in a non-shivering thermogenic capacity, also performs as an endocrine organ, and assists with glucose homeostatsis and insulin sensitivity. Positron emission tomography (PET)-computed tomography (CT) imaging has identified depots of BAT in humans, igniting scientific interest. Our understanding of human BAT is limited because the primary technique for detecting BAT is through 18F-fluorodeoxyglucose (18F-FDG) PET-CT. Although useful for detecting active BAT glucose metabolism, it disregards the fatty acid substrate fuel, and is limited due to the use of ionizing radiation. Therefore to fully understand the function of BAT and its role in whole body energy metabolism, new imaging techniques need to be employed. The purpose of this dissertation is to characterize both active and inactive supraclavicular BAT in adults, and compare the values to those of subcutaneous white adipose tissue (WAT). We obtained 18F-FDG PET-CT and magnetic resonance imaging (MRI) scans of healthy adults. Unlike 18F-FDG PET, which can only detect active BAT, we show MRI is detects both active and inactive BAT. The MRI derived fat-signal fraction (FSF) of active BAT was significantly lower than inactive BAT (mean ± SD): 60.2 ± 7.6% vs. 62.4 ± 6.8%, respectively. This change in tissue morphology was also reflected as a significant increase in Hounsfield Units (HU): -69.4 ± 11.5 HU vs. -74.5 ± 9.7 HU, respectively. Additionally, the CT HU, MRI FSF and MRI R2* values are significantly different between BAT and WAT, regardless of the activation status of BAT. To the best of our knowledge this is the first study to quantify PET-CT and MRI measures of BAT in both active and inactive states in the same adult subjects. Our findings support the use of these metrics to characterize and distinguish between BAT and WAT, and lay the foundation for future MRI analysis with the hope that someday MRI-based delineation of BAT can stand on its own.
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