Fibre orientation of fresh and frozen porcine aorta determined non-invasively using diffusion tensor imaging

Diffusion tensor imaging analysis was applied to fresh and frozen porcine aortas in order to determine fibre orientation. Fresh and stored frozen porcine aortas were imaged in a 7 T scanner with a diffusion weighted spin echo sequence (six gradient directions, matrix 128×128 pixels, 2.8 cm×2.8 cm field of view). The images were taken for different b values, ranging from 200 s/mm(2) to 1600 s/mm(2). For each dataset the diffusion tensor was evaluated, fractional anisotropy (FA) maps were calculated, and the fibres mapped. The arterial fibres resulting were postprocessed and their fibre angle evaluated. The FA maps, the dominant fibre angle, and the fibre pattern in the arterial wall thickness were compared in the fresh and in the stored frozen aortas. The technique was able to determine a fibre pattern in the fresh healthy aorta that is in accordance with the data available in literature and to identify an alteration in the fibre pattern caused by freezing. This study shows that this technique has potential for studying fibre orientation and fibre distribution in humans and could be further developed to diagnose fibre alterations due to cardiovascular diseases. In fact, our results suggest that DTI has the potential to determine the fibrous structure of arteries non-invasively. This capability could be further developed to study the natural remodelling of the aorta in vivo due to age and/or gender or to obtain information on aortic diseases at an early stage of their evolution.