Comparative localized linear accuracy of small-field cone-beam CT and multislice CT for alveolar bone measurements M. Loubele, MSc, a N. Van Assche, MD, b K. Carpentier, b F. Maes, MSc, PhD, a R. Jacobs, MD, PhD, c D. van Steenberghe, MD, PhD, b and P. Suetens, MSc, PhD, a Leuven, Belgium KATHOLIEKE UNIVERSITEIT LEUVEN Objectives. To compare the accuracy of cone-beam computerized tomography (CBCT) and multislice CT (MSCT) for linear jaw bone measurements. Study design. An ex vivo formalin-fixed human maxilla was imaged with both CBCT (Accuitomo 3D; Morita, Kyoto, Japan) and MSCT (4-slice Somatom VolumeZoom and 16-slice Somatom Sensation 16; Siemens, Erlangen, Germany). The MSCT images were reconstructed using different reconstruction filters to optimize bone visualization (U70u and U90u for VolumeZoom, H30s and H60s for Sensation 16). Before scanning, triplets of small gutta-percha markers were glued onto the soft tissues overlying the maxillary bone on the top and on both sides of the alveolar ridge to define a set of reproducible linear measurements in 11 planes. Image measurements were performed by 2 observers. The gold standard was determined by means of physical measurements with a caliper by 3 observers. Results. The accuracy of the linear measurements was 0.35  1.31 mm (U70u) and 0.06  1.23 mm (U90u) for the Somatom VolumeZoom, 0.24  1.20 mm (H60s) and 0.54  1.14 mm (H30s) for the Sensation 16, and -0.09  1.64 mm for the Accuitomo 3D. Statistical analysis with 2-way analysis of variance showed no significant inter- or intraobserver disagreement for the physical or the radiologic measurements. There was also no significant difference for the measurements on the different reconstruction filters. Conclusion. Both CBCT and MSCT yield submillimeter accuracy for linear measurements on an ex vivo specimen. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:512-8) During the last decade, there has been a growing trend to use 3-dimensional (3D) imaging to improve den- tomaxillofacial diagnosis. At first, this was achieved by the use of conventional single and later multislice com- puterized tomography (MSCT). 1,2 Because conven- tional CT protocols are generally associated with rela- tively high radiation dose levels, 3 alternative CT protocols for facial bone visualization and modeling have been developed to deal with this issue without significant loss of image quality. 4,5 In this respect, cone-beam CT (CBCT) holds promising potential for oral and craniofacial imaging applications. 6,7 Overall advantages of the CBCT technique are a lower radia- tion dose, a shorter acquisition time, and reduced costs. 6-10 On the other hand, disadvantages include scatter radiation, 11 the limited dynamic range of the x-ray area detectors, the truncated view artefact, 8 and artefacts caused by beam hardening. 12,13 These draw- backs may influence image quality and/or applicability. Because clinicians often use linear measurements, such as distances between anatomic landmarks or bone thicknesses, for aiding diagnosis and for determining presurgical strategies, 14-17 it is evident that one should determine the accuracy of such measurements from CBCT images. In general, 3 different methodologies can be applied for assessing the accuracy of image- based measurements: use of geometrical hardware phantoms, 17 with anthropomorphic phantoms, 18 and comparison of the new experimental imaging modality (in casu CBCT) with an existing clinically established imaging modality (MSCT). 19 For each of these ap- proaches a ground truth needs to be defined, and a reliable method of comparing the image data to this ground truth needs to be provided. Establishing a 3D geometric ground truth with suf- ficient accuracy and detail is not straightforward for complexly shaped anatomic objects and not possible for clinical patient imaging. Therefore, Marmulla et al. 17 used a geometrical phantom with accurately known dimensions to evaluate the accuracy of the Newtom 9000 CBCT scanner (Quantitative Radiology, Verona, Italy) by comparison of landmark positions extracted from the image data with their known position in the Dr van Steenberghe is the Brånemark Chair for Osseointegration. a Medical Image Computing (ESAT/PSI), Faculty of Engineering. b Department of Periodontology, Faculty of Medicine. c Oral Imaging Center, Faculty of Medicine. Received for publication Apr 14, 2006; returned for revision Apr 9, 2007; accepted for publication May 3, 2007. 1079-2104/$ - see front matter © 2008 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2007.05.004 512