Comparison of Cone-Beam CT, Photon-Counting Detector CT and Micro-CT for Imaging Bone Graft Biomaterials and Three-Dimensional Printed Calcium Phosphate Scaffolds: An Ex Vivo Study

Background/Objectives: Cone-beam computed tomography (CBCT) is widely used in dentomaxillofacial imaging for evaluating bone grafts and implant-related procedures; however, image quality is often compromised by metal-induced artefacts. This study compared CBCT, photon-counting detector CT (PCD-CT), and micro-computed tomography (µCT) for imaging clinically relevant bone graft materials and three-dimensional printed calcium phosphate scaffolds, focusing on biomaterial visualisation and titanium artefact reduction. Methods: Four bovine mandibles were prepared with standardized cylindrical defects containing eight bone substitute materials and 3D-printed calcium phosphate scaffolds, with or without surrounding titanium cages. Specimens were imaged using CBCT and PCD-CT with low-dose and maximum-dose ultra-high-resolution acquisition protocols, and µCT. Two readers independently assessed image interpretability, biomaterial visualisation, and metal artefact severity using a five-point scoring system. Inter-reader agreement was evaluated using weighted Cohen’s kappa. Results: µCT provided the highest spatial resolution and served as the ex vivo reference standard. Under the acquisition and reconstruction protocols evaluated, PCD-CT provided favorable visualization of scaffold architecture and reduced the visual impact of titanium-induced artefacts compared with CBCT. High-energy virtual monoenergetic reconstructions (≥130 keV) further reduced beam-hardening and streak artefacts, although the optimal reconstruction energy may depend on the biomaterial and diagnostic task. Without titanium cages, PCD-CT and µCT achieved higher image interpretability scores than CBCT. With titanium cages, CBCT frequently became non-diagnostic, whereas PCD-CT maintained good visualisation of most biomaterials. Inter-reader agreement ranged from substantial to almost perfect. Conclusions: In this exploratory ex vivo study, the evaluated PCD-CT protocols provided favorable qualitative visualization of several bone graft materials and three-dimensional printed calcium phosphate scaffolds compared with the evaluated CBCT protocol, particularly in the presence of titanium cages. However, the protocols were not dose-matched, and differences in acquisition and reconstruction parameters prevent attributing the observed findings exclusively to detector technology. The study does not establish PCD-CT superiority at equivalent radiation doses or demonstrate clinical performance in longitudinal bone-regeneration monitoring. Further dose-matched studies incorporating objective image-quality measurements and clinical validation are required.