DEVELOPMENT OF A PROCEDURE FOR INCREASING THE ACCURACY OF THE RECONSTRUCTION AND TRIANGULATION PROCESS OF THE CRANIAL VAULT GEOMETRY FOR ADDITIVE MANUFACTURING

CT scanners installed in clinics used different slice thicknesses, which usually produce data with an anisotropic structure of voxels. The low visual quality results are due to the discontinuous interpolation between neighboring voxels, resulting in a very “blocky” appearance of the reconstructed surfaces (stair-step artifact). This structure can also directly affect the volume, geometry, and linear accuracy of digital and physical 3D models. The article presents a method that improves the design of cranial vault models for additive manufacturing after the staircase artifact has occurred. The research was performed on 14 different patients (seven males and seven females). Changing the slice thickness from 2.4 mm to 4.8 mm generated over 90% errors in reconstructing the cranial vault area in the range of 0.830 mm +/- 1.364 mm (mean deviation +/- expanded uncertainty) for males and 0.780 mm +/- 1.338 mm for females. To increase the spatial resolution of the digital imaging data, an interpolation process was performed on 2D radiographic images. After using the data interpolation procedure (Lanczos filter), deviations were mainly in the range of 0.465 mm +/- 1.038 mm for males and 0.328 mm +/- 0.842 mm for females. The last stage of the improved process involved mesh optimization. Utilizing Laplacian smoothing surface and isotropic polygonal remesh, this procedure decreased global error, especially in regions with high curvatures. Over 90% of the analyzed points after using the Lanczos filter and optimization mesh procedure are within the range of 0.338 mm +/- 1.014 mm for males and 0.301 mm +/- 0.806 mm for females.