Analysis of the accuracy of linear measurements obtained by cone beam computed tomography (CBCT-NewTom)

The conical beam computed tomography (CBCT) technique presents an innovation of tomographic imaging systems and subsequent volumetric image reconstruction for dentistry. When compared with other methods of tomographic imaging CBCT is characterized by rapid volumetric image acquisition from a single low radiation dose scan of the patient. The NewTom (NewTom 9000; Quantitative Radiology, Verona, Italy) is an example of such a CBCT machine dedicated to dental and maxillofacial imaging, particularly for surgical and/or prosthetics implant planning in the field of dentistry. The aim of this study was to evaluate the accuracy of the linear measurements obtained in CBCT images using a NewTom.

Thirteen measurements were obtained in dry skulls (n = 8) between internal and external anatomical sites using a caliper. These were considered as real measurements. Then the dry skulls were submitted to CBCT imaging examinations. Radiographic distance measurements of the same dry skull anatomical sites were made using the NewTom QR-DVT 9000 software of the 2 mm-CTs axial section images and sagittal or coronal reconstructions. The data were compared by paired Student's t-test.

The results showed that the real measurements were always larger than those for the CBCT images, but these differences were only significant for measurements of the internal structures of the skull base.

The conclusion of this study is that, although the CBCT image underestimates the real distances between skull sites, differences are only significant for the skull base and therefore it is reliable for linear evaluation measurements of other structures more closely associated with dentomaxillofacial imaging.