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.

Effect of voltage and amperage alterations in CBCT on metal artifact generation caused by exomass

“…Another study evaluated the effect of presence of three titanium implants in the exomass using Cranex, 3Dx, Orthopos SL-3D, and XI scanners and reported a signi cant reduction in the mean GV compared with the control position [27]. Consistent with the present ndings, Sa et al [22] reported the highest reduction in the mean GV due to the presence of amalgam alloy, and the lowest reduction due to the presence of titanium implants in the exomass area.…”

“…Using the smallest possible FOV has been recommended to protect against ionizing radiation and improve image quality [30,32]. However, in CBCT, reduction in size of FOV in the axial plane indirectly increases the exomass effect and occurrence of truncation [22,24,31,33], and heterogeneity in the reconstructed volume [34]. It should be noted that all previous studies on exomass artifacts used metal objects of the same volume and dimensions [11,15,16,27,28,35,36], which is different from the clinical setting.…”

“…Moreover, the results revealed the poorest image quality in presence of amalgam in the exomass area, compared with the other two metal objects. Sa et al [22] showed that type and number of metal objects affected the artifacts caused by the metal objects in the exomass area.…”

Influence of metal artefact reduction on the diagnosis of contact between implant and mandibular canal in cone beam computed tomography: An ex‐vivo study

“…Previous studies have investigated CBCT-related parameters in artefact generation, such as tube current (mA), field of view (FOV), tube voltage (kV) and CBCT unit-specific factors (Codari et al, 2017;Freitas et al, 2018;Pauwels et al, 2013;Safi et al, 2022;Sawicki et al, 2022;Schulze et al, 2010Schulze et al, , 2011Wanderley et al, 2021).…”

“…Previous studies have investigated CBCT‐related parameters in artefact generation, such as tube current (mA), field of view (FOV), tube voltage (kV) and CBCT unit‐specific factors (Codari et al, 2017; Freitas et al, 2018; Pauwels et al, 2013; Safi et al, 2022; Sawicki et al, 2022; Schulze et al, 2010, 2011; Wanderley et al, 2021). Artefact generation has been studied and related to the CBCT unit (Freitas et al, 2018; Vasconcelos et al, 2019; De Faria Vasconcelos et al, 2020), artefact‐generating material (Queiroz et al, 2018; Vasconcelos et al, 2019; De Faria Vasconcelos et al, 2020; Mancini et al, 2021), positioning (Vasconcelos et al, 2019) and scanning protocol (Freitas et al, 2018; Khosravifard et al, 2021; Mancini et al, 2021; Vasconcelos et al, 2019).…”