Multi-Stage micro-CT-based dimensional accuracy assessment of a voronoi-based patient-specific cranial implant fabricated by electron beam melting.

Introduction: Patient-specific cranial implants fabricated using powder bed fusion technologies require rigorous dimensional validation to ensure reliable digital-to-physical translation, particularly when complex architectures are employed. However, multistage quantitative evaluations that distinguish deviations introduced during additive manufacturing and post-processing remain limited. Methods: A multistage dimensional accuracy assessment workflow based on high-resolution micro-computed tomography (micro-CT) was applied to a representative patient-specific cranial implant featuring a Voronoi-based macrostructure fabricated in Ti-6Al-4 V using Electron Beam Melting (EBM). The implant was digitized in the unpolished and surface-finished conditions. Three-dimensional surface models were compared with the original virtual design using full-field deviation analysis to quantify geometric variations attributable to manufacturing and post-processing. Results: After the finishing procedure, the surface roughness decreased significantly, with Ra reduced from 19.41 µm to 1.43 µm and Rz from 83.28 µm to 6.31 µm. A comparison between the virtual model and the unpolished implant revealed dimensional deviations predominantly within -0.20 to +0.35 mm, with localized positive deviations up to +0.55 mm associated with powder adhesion and support interaction. Following post-processing, deviations shifted predominantly toward negative values owing to controlled material removal, with a mean deviation of -0.05 mm and a maximum negative deviation of -0.18 mm. Surface finishing reduced the maximum positive deviation from +0.55 mm to +0.04 mm, corresponding to an approximate 93% reduction in positive dimensional deviation. The overall topology and structural continuity of the Voronoi-based architecture were preserved throughout manufacturing and finishing. Discussion: This proof-of-concept study demonstrated the feasibility of a multistage micro-CT-based workflow for the dimensional validation of complex patient-specific cranial implants fabricated by EBM. The proposed methodology enables differentiation between manufacturing- and post-processing-induced deviations and supports reproducible quality assessment of additively manufactured cranial implant geometries.