Effect of the Field of View Size on CBCT Artifacts Caused by the Presence of Metal Objects in the Exomass

Abstract

Background and Aim. This study aimed to assess the effect of the size of the field of view (FOV) on cone-beam computed tomography (CBCT) artifacts caused by metal objects in the exomass. Materials and Methods. In this in vitro experimental study, titanium implants, teeth with cobalt-chromium (Co-Cr) intracanal posts, and teeth with mesio-occluso-distal (MOD) amalgam restorations were placed in an empty socket of the extracted third molar of a human mandible. These metallic materials were differently arranged in the exomass (zone outside of the FOV). A polypropylene tube containing dipotassium phosphate was placed in the empty socket of the right canine tooth in a dry human mandible. CBCT scans were taken with a NewTom VGI (Verona, Italy) scanner using a 6 × 6 cm and an 8 × 8 cm FOV. The histogram tool of OnDemand software (Cybermed, Seoul, Korea) was used to select circles with a 1.5 mm diameter as the (ROI) at the center of the homogenous solution of dipotassium phosphate tube on the axial plane. The mean gray value (GV) and its standard deviation (SD) in the region of interest (ROI) were calculated ( $P>0.05$ ). The data were analyzed by SPSS 26. Results. The reduction in the size of the FOV significantly decreased the mean GV ( $P<0.001$ ). Metal objects in the exomass significantly decreased the mean GV ( $P<0.001$ ), and minimum mean GV and maximum SD were recorded for amalgam, followed by Co-Cr intracanal posts, and titanium implants. The unilateral presence of a metal object was associated with a higher mean GV and lower SD ( $P<0.001$ ). Conclusion. Using a smaller FOV increases the size of the exomass, which may negatively affect the image quality. Metal objects in the exomass decrease the GV of CBCT scans and adversely affect the image quality.