Assessment of Body Composition Using Magnetic Resonance Imaging

Methods for assessment of body composition allow studies of the complex relationships between body composition and the wellbeing of humans. The amount and distribution of adipose tissue is of great importance in these studies. This thesis describes, proposes, and evaluates new methods for assessment of body composition (amount and distribution of adipose tissue) using magnetic resonance imaging (MRI). The thesis focuses on the use of MRI but includes results from computed tomography (CT) and dual energy X-ray absorptiometry (DEXA). The subject data used originates from cohorts recruited solely for the purpose of the included studies and from the “Prospective Investigation of Vasculature in Uppsala Seniors” (PIVUS) and the Sib-pair (within the framework of the Swedish Obese Subjects - SOS study) studies. The included studies propose a new acquisition method for whole-body analysis of adipose tissue, a fully automated post processing algorithm for segmentation of visceral and subcutaneous adipose tissue from abdominal MRI data, and anthropometrical measurements for practical estimations of body composition. The proposed acquisition method for whole-body adipose tissue analysis simplified the analysis of adipose tissue and the results strongly correlated with the results from CT and DEXA analysis. The fully automated post processing algorithm gave reproducible results with relatively high accuracy. Transverse and sagittal abdominal diameters gave information about subcutaneous and visceral adipose tissue, respectively, and an elliptical approximation was found useful in estimation of total amount of abdominal adipose tissue. The methods proposed in this thesis were found useful for assessment of body composition. The methods were developed with clinical practice in mind and all proposed methods have been used in further studies for assessment of body composition