To use a computerized shape-from-shading technique to characterize the topography of the small intestinal mucosa. METHODSVideoclips comprised of 100-200 images each were obtained from the distal duodenum in 8 celiac a...To use a computerized shape-from-shading technique to characterize the topography of the small intestinal mucosa. METHODSVideoclips comprised of 100-200 images each were obtained from the distal duodenum in 8 celiac and 8 control patients. Images with high texture were selected from each videoclip and projected from two to three dimensions by using grayscale pixel brightness as the Z-axis spatial variable. The resulting images for celiac patients were then ordered using the Marsh score to estimate the degree of villous atrophy, and compared with control data. RESULTSTopographic changes in celiac patient three-dimensional constructs were often more variable as compared to controls. The mean absolute derivative in elevation was 2.34 ± 0.35 brightness units for celiacs vs 1.95 ± 0.28 for controls (P = 0.014). The standard deviation of the derivative in elevation was 4.87 ± 0.35 brightness units for celiacs vs 4.47 ± 0.36 for controls (P = 0.023). Celiac patients with Marsh IIIC villous atrophy tended to have the largest topographic changes. Plotted in two dimensions, celiac data could be separated from controls with 80% sensitivity and specificity. CONCLUSIONUse of shape-from-shading to construct three-dimensional projections approximating the actual spatial geometry of the small intestinal substrate is useful to observe features not readily apparent in two-dimensional videocapsule images. This method represents a potentially helpful adjunct to detect areas of pathology during videocapsule analysis.展开更多
Shape-from-shading(SFS) is one of the important approaches of 3-D surface reconstruction in computer vision. Since reflectance map equation in SFS is a nonlinear partial differential equation(PDE) with two unknown var...Shape-from-shading(SFS) is one of the important approaches of 3-D surface reconstruction in computer vision. Since reflectance map equation in SFS is a nonlinear partial differential equation(PDE) with two unknown variables, SFS with one image is ill-posed in mathematical sense. A linear perspective SFS method with two images is proposed to deal with the problem. We assume that two images with different light source directions are captured firstly. Orthogonal projection is not as accurate as perspective one to simulate imaging processes. Two reflectance map equations are established based on the Lambertian model under perspective projection, and the equations are further transformed into one linear PDE. Then the iterative semi-Lagrangian algorithm is used to approximate the solution. Finally, 3-D height values of pixel points in imaging planes are solved by the numerical interpolation method. Experimental results of both hemisphere and complex surfaces show that the proposed method can reconstruct surfaces accurately.展开更多
This paper translates the recognifion of curvatare radius in robot moving in bent pipe into an issue of shape-from-shading, and introduces genetic algorithms into the optimizaton process to improve the efficiency of o...This paper translates the recognifion of curvatare radius in robot moving in bent pipe into an issue of shape-from-shading, and introduces genetic algorithms into the optimizaton process to improve the efficiency of optimization.Experiments prove that thes method can satisfy the autonomous control requrement for robot moving in bent pipe in both speed and accuray.展开更多
文摘To use a computerized shape-from-shading technique to characterize the topography of the small intestinal mucosa. METHODSVideoclips comprised of 100-200 images each were obtained from the distal duodenum in 8 celiac and 8 control patients. Images with high texture were selected from each videoclip and projected from two to three dimensions by using grayscale pixel brightness as the Z-axis spatial variable. The resulting images for celiac patients were then ordered using the Marsh score to estimate the degree of villous atrophy, and compared with control data. RESULTSTopographic changes in celiac patient three-dimensional constructs were often more variable as compared to controls. The mean absolute derivative in elevation was 2.34 ± 0.35 brightness units for celiacs vs 1.95 ± 0.28 for controls (P = 0.014). The standard deviation of the derivative in elevation was 4.87 ± 0.35 brightness units for celiacs vs 4.47 ± 0.36 for controls (P = 0.023). Celiac patients with Marsh IIIC villous atrophy tended to have the largest topographic changes. Plotted in two dimensions, celiac data could be separated from controls with 80% sensitivity and specificity. CONCLUSIONUse of shape-from-shading to construct three-dimensional projections approximating the actual spatial geometry of the small intestinal substrate is useful to observe features not readily apparent in two-dimensional videocapsule images. This method represents a potentially helpful adjunct to detect areas of pathology during videocapsule analysis.
基金supported by the National Natural Science Foundation of China(61005015)the Third National Post-Doctoral Special Foundation of China(201003280)
文摘Shape-from-shading(SFS) is one of the important approaches of 3-D surface reconstruction in computer vision. Since reflectance map equation in SFS is a nonlinear partial differential equation(PDE) with two unknown variables, SFS with one image is ill-posed in mathematical sense. A linear perspective SFS method with two images is proposed to deal with the problem. We assume that two images with different light source directions are captured firstly. Orthogonal projection is not as accurate as perspective one to simulate imaging processes. Two reflectance map equations are established based on the Lambertian model under perspective projection, and the equations are further transformed into one linear PDE. Then the iterative semi-Lagrangian algorithm is used to approximate the solution. Finally, 3-D height values of pixel points in imaging planes are solved by the numerical interpolation method. Experimental results of both hemisphere and complex surfaces show that the proposed method can reconstruct surfaces accurately.
文摘This paper translates the recognifion of curvatare radius in robot moving in bent pipe into an issue of shape-from-shading, and introduces genetic algorithms into the optimizaton process to improve the efficiency of optimization.Experiments prove that thes method can satisfy the autonomous control requrement for robot moving in bent pipe in both speed and accuray.
