Level-set segmentation of pulmonary nodules in radiographs using a CT prior

Jay S. Schildkraut; Shoupu Chen; Michael Heath; Walter G. O'Dell; Paul Okunieff M.D.; M. C. Schell; Narinder Paul

doi:10.1117/12.808288

27 March 2009 Level-set segmentation of pulmonary nodules in radiographs using a CT prior

Jay S. Schildkraut, Shoupu Chen, Michael Heath, Walter G. O'Dell, Paul Okunieff M.D., M. C. Schell, Narinder Paul

Proceedings Volume 7259, Medical Imaging 2009: Image Processing; 72593B (2009) https://doi.org/10.1117/12.808288
Event: SPIE Medical Imaging, 2009, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

This research addresses the problem of determining the location of a pulmonary nodule in a radiograph with the aid of a pre-existing computed tomographic (CT) scan. The nodule is segmented in the radiograph using a level set segmentation method that incorporates characteristics of the nodule in a digitally reconstructed radiograph (DRR) that is calculated from the CT scan. The segmentation method includes two new level set energy terms. The contrast energy seeks to increase the contrast of the segmented region relative to its surroundings. The gradient direction convergence energy is minimized when the intensity gradient direction in the region converges to a point. The segmentation method was tested on 23 pulmonary nodules from 20 cases for which both a radiographic image and CT scan were collected. The mean nodule effective diameter is 22.5 mm. The smallest nodule has an effective diameter of 12.0 mm and the largest an effective diameter of 48.1 mm. Nodule position uncertainty was simulated by randomly offsetting the true nodule center from an aim point. The segmented region is initialized to a circle centered at the aim point with a radius that is equal to the effective radius of the nodule plus a 10.0 mm margin. When the segmented region that is produced by the proposed method is used to localize the nodule, the average reduction in nodule-position uncertainty is 46%. The relevance of this method to the detection of radiotherapy targets at the time of treatment is discussed.

Citation Download Citation

Jay S. Schildkraut, Shoupu Chen, Michael Heath, Walter G. O'Dell, Paul Okunieff M.D., M. C. Schell, and Narinder Paul "Level-set segmentation of pulmonary nodules in radiographs using a CT prior", Proc. SPIE 7259, Medical Imaging 2009: Image Processing, 72593B (27 March 2009); https://doi.org/10.1117/12.808288

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