4D Warping for Analysing Morphological Changes in Seed Development of Barley Grains

NMR imaging allows to obtain 3D-images by non-invasive treatment of biological structures. In this study intensity-based warping is evaluated by comparing it to landmark-based warping for a four-dimensional analysis of morphological changes in seed development of barley. The datasets of barley grains are obtained at certain development stages by NMR. Warping algorithms reconstruct intermediate physically nonmeasured stages. The landmark-based procedure consists of automatic definition of landmarks and subsequent distance-weighted warping. The intensity-based approach uses iterative intensity-based warping for definition of the displacement vector field and distance-weighted volume warping for generation of the virtual intermediate dataset. The approaches were tested with four datasets of barley at different development stages. As a result, the intensity-based approach is highly applicable for analysis of morphological changes in NMR datasets and serves as a tool for an extensive 4D analysis of seed development in barley grains.