Maureen van Eijnatten1, Jan Wolff2, Ruben Pauwels3,4, Kalle Karhu5, Ari Hietanen6, Henry der Sarkissian7, Juha H Koivisto8. 1. Department of Oral and Maxillofacial Surgery/Oral Pathology, 3D Innovation Lab, Amsterdam UMC (location: VUmc), Amsterdam, The Netherlands. 2. Department of Dentistry and Oral Health Section of Oral and Maxillofacial Surgery and Oral Pathology, Aarhus University Vennelyst Boulevard , Aarhus C, Denmark. 3. Aarhus Institute of Advanced Studies Aarhus University Høegh-Guldbergs Gade 6B, Aarhus, Denmark. 4. Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand. 5. Varjo Oy Vuorikatu 20, FIN-00100, Helsinki, Finland. 6. Planmeca Oy Asentajankatu 6, FIN-00880, Helsinki, Finland. 7. Centrum Wiskunde & Informatica, Amsterdam, The Netherlands. 8. Department of Physics, University of Helsinki Gustaf Hällströmin katu 2, Helsinki, Finland.
Abstract
OBJECTIVE: Cone beam computed tomography (CBCT) images are being increasingly used to acquire three-dimensional (3D) models of the skull for additive manufacturing purposes. However, the accuracy of such models remains a challenge, especially in the orbital area. The aim of this study is to assess the impact of four different CBCT imaging positions on the accuracy of the resulting 3D models in the orbital area. METHODS: An anthropomorphic head phantom was manufactured by submerging a dry human skull in silicon to mimic the soft tissue attenuation and scattering properties of the human head. The phantom was scanned on a ProMax 3D MAX CBCT scanner using 90 and 120 kV for four different field of view positions: standard; elevated; backwards tilted; and forward tilted. All CBCT images were subsequently converted into 3D models and geometrically compared with a "gold-standard" optical scan of the dry skull. RESULTS: Mean absolute deviations of the 3D models ranged between 0.15 ± 0.11 mm and 0.56 ± 0.28 mm. The elevated imaging position in combination with 120 kV tube voltage resulted in an improved representation of the orbital walls in the resulting 3D model without compromising the accuracy. CONCLUSIONS: Head positioning during CBCT imaging can influence the accuracy of the resulting 3D model. The accuracy of such models may be improved by positioning the region of interest (e.g. the orbital area) in the focal plane (Figure 2a) of the CBCT X-ray beam.
OBJECTIVE: Cone beam computed tomography (CBCT) images are being increasingly used to acquire three-dimensional (3D) models of the skull for additive manufacturing purposes. However, the accuracy of such models remains a challenge, especially in the orbital area. The aim of this study is to assess the impact of four different CBCT imaging positions on the accuracy of the resulting 3D models in the orbital area. METHODS: An anthropomorphic head phantom was manufactured by submerging a dry human skull in silicon to mimic the soft tissue attenuation and scattering properties of the human head. The phantom was scanned on a ProMax 3D MAX CBCT scanner using 90 and 120 kV for four different field of view positions: standard; elevated; backwards tilted; and forward tilted. All CBCT images were subsequently converted into 3D models and geometrically compared with a "gold-standard" optical scan of the dry skull. RESULTS: Mean absolute deviations of the 3D models ranged between 0.15 ± 0.11 mm and 0.56 ± 0.28 mm. The elevated imaging position in combination with 120 kV tube voltage resulted in an improved representation of the orbital walls in the resulting 3D model without compromising the accuracy. CONCLUSIONS: Head positioning during CBCT imaging can influence the accuracy of the resulting 3D model. The accuracy of such models may be improved by positioning the region of interest (e.g. the orbital area) in the focal plane (Figure 2a) of the CBCT X-ray beam.
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