ABSTRACT
Objectives: 'Field of view (FOV) size' affects the quality of radiographic images and the radiation dose received by patients. In cone-beam computed tomography (CBCT) FOV should be selected according to therapeutic purposes. While aiming for the highest diagnostic image quality, the radiation dose should be kept to a minimum to reduce the risk for patients. The purpose of this study was to assess the effect of different sizes of FOV on contrast-to-noise ratio (CNR) in five different CBCT units. Materials and Methods: In this experimental study, CBCT scans were taken from a dried human mandible containing a resin block fixed to the lingual cortex and a resin ring was used to simulate soft tissue during scans. Five CBCT units including, NewTom VGi, NewTom GiANO, Soredex SCANORA 3D, Planmeca ProMax, and Asahi Alphard 3030 were evaluated. Each unit had 3 to 5 different FOVs. Images were obtained and analyzed with ImageJ software and CNR was calculated in each image. ANOVA and T-test were used for statistical analysis (P<0.05). Results: Comparison among different FOVs of each unit showed significant CNR reductions in small FOVs (P<0.05). Similar FOV sizes of different CBCT devices were also compared and demonstrated significant differences (P<0.05). Conclusion: A direct relationship between FOV size and CNR was observed in all five CBCT units, but differences in exposure parameters of these units led to variable CNR in FOVs with similar sizes.
ABSTRACT
INTRODUCTION: Presence of the maxillary sinus septum would increase the risk of sinus membrane perforation during sinus floor elevation surgery. Three-dimensional radiographic techniques are recommended for the evaluation of the maxillary sinuses. MATERIALS AND METHODS: This cross-sectional study evaluated 946 maxillary sinuses using the cone beam computed tomography. Presence of septa, number, location, height, and orientation were evaluated and recorded in data forms. RESULTS: Of all patients, 44.8% had at least 1 septum; 36.8% had 1 septum in their right maxillary sinus, 27.4% in their left, and 35.8% in both sides. No statistically significant difference was found between males and females or the right and left maxillary sinuses in terms of the prevalence of septa. In 35.1% of patients, the septum was in the middle of the sinus. Mediolateral septa had the highest frequency (59.2%). The highest mean septum height in the medial zone was 6.3 ± 3.1 mm in the right sinus and 7.1 ± 3.1 mm in the left sinus. CONCLUSION: Approximately 45% of patients had at least 1 septum, and this finding emphasizes the need for the assessment of the maxillary sinuses to prevent complications.
