Water-fat magnetic resonance imaging for the assessment of human fetal adipose tissue
Abstract
Adipose tissue is crucial for providing heat and energy to infants, especially at transitions such as birth and therefore must begin developing in utero. This development may be altered due to an adverse uterine environment, increasing the risk of developing later-life metabolic diseases such as obesity. An early assessment of fetal adipose tissue development through lipid accumulation could be key to understanding metabolic programming and minimizing this risk.
Water-fat magnetic resonance imaging (MRI) can non-invasively measure the lipid concentration of tissues and can therefore monitor the development of adipose tissue via tissue lipid concentration. This work demonstrated the feasibility of measuring fetal adipose tissue volumes and lipid concentrations in the third trimester. Both measures increased with gestational age, indicating this technique is sensitive to the tissue expansion and accumulation of lipids within the adipose tissue, an important improvement over previous MRI techniques limited to volume measures only.
Two water-fat MRI techniques were compared for measuring fetal adipose tissue lipid concentration; modified two-point Dixon and chemical-shift encoded MRI. It was found that the two techniques produced reliable fetal adipose tissue lipid concentration measures; however, only chemical-shift encoded MRI is suitable for assessing the lipid concentration of the fetal liver.
A regional variability of fetal adipose tissue lipid concentrations was found, reflecting the different gestational ages that adipose tissue compartments begin developing. Two compartments that begin development simultaneously but contain one of the two main types of adipose tissue, brown (generates heat) and white (stores energy), also had different lipid concentrations. This is an encouraging result suggesting that water-fat MRI could be used to differentiate fetal brown and white adipose tissues.
In conclusion, this dissertation contains applications of water-fat MRI techniques to assess the lipid concentration of fetal adipose tissue. It highlights factors that affect lipid concentration, including gestational age and adipose tissue region and type. These factors, and the choice of water-fat MRI technique, are important considerations for future studies aiming to use fetal tissue lipid concentrations to assess fetal metabolic programming.