Magnetic resonance imaging for the in vivo determination of body composition in animal science

Abstract

Magnetic resonance imaging (MRI) is a diagnostic tool, originally developed for human medicine. It generates cross-sectional images of nearly all parts of the body with a high contrast between soft tissues. In animal science it has been utilized predominantly as an in vivo technique for the determination of body composition. The process of scanning live animals and especially the choice of the optimum measuring parameters is presented as well as methods of quantitative image analysis. Studies in pig and sheep indicate that quantification of lean and fat tissue by means of prediction equations is highly accurate. Coefficients of determination for the amount of lean and fat range between R 2 = 0.89 and R 2 = 0.97 for different weight groups. Direct measurements of breast muscle volume have been carried out in water fowl. Correlation between muscle volume derived from MR images and muscle weight due to dissection is abour r = 0.95. Based on the accurate prediction of lean and fat tissue and the volume measurement of single muscles MRI has been applied in pig, sheep and water fowl to analyse tissue und muscle growth during the fattening period. Influencing factors on growth, such as breed and sex, have been analysed by means of allometric functions. Furthermore in vivo imaging of morphological structures and pathological alterations is discussed.