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Subvoxel accurate graph search using non-Euclidean graph space
Journal article   Open access   Peer reviewed

Subvoxel accurate graph search using non-Euclidean graph space

Michael D Abràmoff, Xiaodong Wu, Kyungmoo Lee and Li Tang
PloS one, Vol.9(10), e107763
2014
DOI: 10.1371/journal.pone.0107763
PMCID: PMC4196762
PMID: 25314272
url
https://doi.org/10.1371/journal.pone.0107763View
Published (Version of record) Open Access

Abstract

Graph search is attractive for the quantitative analysis of volumetric medical images, and especially for layered tissues, because it allows globally optimal solutions in low-order polynomial time. However, because nodes of graphs typically encode evenly distributed voxels of the volume with arcs connecting orthogonally sampled voxels in Euclidean space, segmentation cannot achieve greater precision than a single unit, i.e. the distance between two adjoining nodes, and partial volume effects are ignored. We generalize the graph to non-Euclidean space by allowing non-equidistant spacing between nodes, so that subvoxel accurate segmentation is achievable. Because the number of nodes and edges in the graph remains the same, running time and memory use are similar, while all the advantages of graph search, including global optimality and computational efficiency, are retained. A deformation field calculated from the volume data adaptively changes regional node density so that node density varies with the inverse of the expected cost. We validated our approach using optical coherence tomography (OCT) images of the retina and 3-D MR of the arterial wall, and achieved statistically significant increased accuracy. Our approach allows improved accuracy in volume data acquired with the same hardware, and also, preserved accuracy with lower resolution, more cost-effective, image acquisition equipment. The method is not limited to any specific imaging modality and readily extensible to higher dimensions.
Algorithms Angiography Magnetic Resonance Imaging Retina - diagnostic imaging Tomography, Optical Coherence Humans Imaging, Three-Dimensional

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