Analysis of intensity variability in multislice and cone beam computed tomography.
ABSTRACT The aim of this study was to evaluate the variability of intensity values in cone beam computed tomography (CBCT) imaging compared with multislice computed tomography Hounsfield units (MSCT HU) in order to assess the reliability of density assessments using CBCT images.
A quality control phantom was scanned with an MSCT scanner and five CBCT scanners. In one CBCT scanner, the phantom was scanned repeatedly in the same and in different positions. Images were analyzed using registration to a mathematical model. MSCT images were used as a reference.
Density profiles of MSCT showed stable HU values, whereas in CBCT imaging the intensity values were variable over the profile. Repositioning of the phantom resulted in large fluctuations in intensity values.
The use of intensity values in CBCT images is not reliable, because the values are influenced by device, imaging parameters and positioning.
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ABSTRACT: The purposes of this study were to determine the accuracy of crown and root length measurements of premolars using cone-beam computed tomography (CBCT) and to generate reference CBCT-based data on incisor, canine, and premolar lengths in patients with malocclusions. Imaging was performed using a CBCT scanner with a 0.292-mm voxel size and 12-bit grayscale. The CBCT-based length measurements were compared with direct measurements of 94 subsequently extracted premolars without metal restorations using the paired t-test. Furthermore, the crown and root lengths of incisors, canines, and premolars in 62 Korean patients with malocclusions were measured using CBCT, and Pearson's correlation coefficients were calculated to examine the relationship between the crown and root length measurements of each tooth type. The differences between the CBCT-based and direct measurements of the extracted premolars were not significant, with 95% limits of agreement of -0.90 to 0.90 mm for crown length and -1.23 to 1.18 mm for root length. Weak positive correlations between the crown and root length measurements were observed for the mandibular canine and premolars. The CBCT-based measurements showed a wider range of limits of agreements for root length than for crown length. The CBCT-based data can be used as a reference for evaluating root length and resorption of teeth without metal restorations in patients with malocclusions.Korean Journal of Orthodontics 12/2013; 43(6):271-8. · 0.54 Impact Factor
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ABSTRACT: Objective: The aim of this study was to assess the influence of different object locations within different field of views (FOVs) of two cone-beam CT (CBCT) systems on trabecular bone microstructure measurements of a human mandible.Methods: A block of human dry mandible was scanned at five different locations (center, left, right, anterior and posterior) using five different field of views (FOVs) of two CBCT systems (NewTom 5G and Accuitomo 170). Image analysis software (CTAn software v 1.1) was used to assess the trabecular bone microstructural parameters (thickness = Tb.Th, spacing = Tb.Sp, number= Tb.N, and bone volume density= BV/TV). All measurements were done twice by one trained observer.Result: Tb.Th, Tb.Sp and Tb.N varied significantly across different FOVs in the NewTom 5G (p<0.001) and the Accuitomo 170 (p<0.001). For location, a significant difference was observed only when measuring BV/TV (p= 0.03) using the NewTom 5G.Conclusion: The trabecular bone microstructural measurements obtained from CBCT systems are influenced by the size of FOVs. Not all trabecular bone parameters measured in different CBCT systems are affected when varying the object location within the FOVs.Dentomaxillofacial Radiology 11/2013; · 1.15 Impact Factor
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ABSTRACT: The purpose of this study was to quantitatively evaluate the cortical bone densities of the maxillary and mandibular alveolar processes in adults with different vertical facial types using cone-beam computed tomography (CBCT) images. CBCT images (n = 142) of adult patients (20-45 years) were classified into hypodivergent, normodivergent, and hyperdivergent groups on the basis of linear and angular S-N/Go-Me measurements. The cortical bone densities (in Hounsfield units) at maxillary and mandibular interdental sites from the distal aspect of the canine to the mesial aspect of the second molar were measured on the images. On the maxillary buccal side, female subjects in the hyperdivergent group showed significantly decreased bone density, while in the posterior region, male subjects in the hyperdivergent group displayed significantly decreased bone density when compared with corresponding subjects in the other groups (p<0.001). Furthermore, the subjects in the hyperdivergent group had significantly lower bone densities on the mandibular buccal side than hypodivergent subjects. The maxillary palatal bone density did not differ significantly among groups, but female subjects showed significantly denser palatal cortical bone. No significant difference in bone density was found between the palatal and buccal sides in the maxillary premolar region. Overall, the palatal cortical bone was denser anteriorly and buccal cortical bone was denser posteriorly. Adults with the hyperdivergent facial type tend to have less-dense buccal cortical bone in the maxillary and mandibular alveolar processes. Clinicians should be aware of the variability of cortical bone densities at mini-implant placement sites.Korean Journal of Orthodontics 01/2014; 44(1):36-43. · 0.54 Impact Factor