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10 March 2006 Alignment of full and partial CT thoracic scans using bony structures
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Diagnostic thoracic procedures using computed tomography (CT) often include comparisons of scans acquired with different slice thicknesses. In this manuscript, we investigated the potential for alignment of different CT scans from the same patient using skeletal knowledge of the thoracic region. Skeletal matching was selected because it is expected to be less susceptible to differences associated with patient breath hold, positioning and cardiac motion. Our method utilized the positioning of the ribs relative to the vertebra for matching. It also included matching the scapula when visible in the scans. Rib positioning was described by the angles formed between the vertebra centroid and combinations of pairs of rib centroids visible on each CT slice; this was used as the primary matching mechanism. Scapula morphology was described using a feature based on the local maxima of the distance transform. Since the scapula is not visible in all slices of a full scan, its description was limited to only defining the potential range of slices. A cost function incorporating the difference of features from rib positioning and scapula morphology between two slices was derived and used to match slices. The method was evaluated on an independent set of 10 pairs of full and partial CT scans. Assessment was based on whether or not slices containing known nodules between each pair of scans were overlapping after the alignment procedure. Results showed that the proposed metric correctly aligned 9 out of 10 scans. The preliminary results are encouraging for using this method as a first step towards temporal analysis of lung nodules.
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Marios A. Gavrielides, Nicholas Petrick, and Kyle J. Myers "Alignment of full and partial CT thoracic scans using bony structures", Proc. SPIE 6144, Medical Imaging 2006: Image Processing, 61443A (10 March 2006);

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