Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible

Abstract

Objectives: The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible. Methods: Ten mandibular sections from cadavers (81.5 6 12.1 years) were scanned using micro-CT with 27.2 mm voxel size and cone beam CT (CBCT) with 200 mm, 300 mm, and 400 mm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 6 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low 5 ) and high (High 5 ) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed. Results: The alveolar bone region had significantly lower Mean, Low 5 and High 5 values but significantly higher SD and COV than the basal cortical bone region for all CT images (p , 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p , 0.05). Conclusions: CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.

Conditions and calibration to obtain comparable grey values between different clinical cone beam computed tomography scanners

“…The anatomical regions investigated in the present study represent clinically important locations to measure BMD for the diagnoses of cervical vertebral maturation (C2), TMJ disorder (RC and LC), dental implantation site and periodontal disease (AB and CB). 20,21,[23][24][25] Alteration of BMD is associated with bone growth, bone disease and post-implantation bone healing. As the CBCT grey value is proportional to BMD, the grey value parameters account for the BMD distribution at the region of interest, which results from bone modelling and remodelling activities observed in clinical settings.…”

“…Non-bone voxels outside of these regions were removed using a heuristic segmentation algorithm, as described in the previous studies. [20][21][22] The TMJ condyles were dissected parallel to the occlusal plane at 7 mm down from top surface. The first premolars were semiautomatically separated from the mandible using differences of grey values between these adjacent local regions.…”

Comparison of 2 root surface area measurement methods: 3-dimensional laser scanning and cone-beam computed tomography

“…Gu et al11 investigated the influence of root variations on the root surface area by using micro-computed tomography (micro-CT) of the extracted teeth and found that micro-CT was a precise technique for root surface area measurement. The quality and resolution of micro-CT images were better than those of CBCT images 1213. In our study, 3D laser scanning was considered to be a highly reliable and accurate technique because of the high resolution of the 3D laser scanner.…”

The Use of Relative Voxel Grey Values in CBCT to Evaluate Radiological Bone Density in the Mandible

“…Bone structure rich in micro structural connections will result in higher grey values. The literature shows that direct comparison of grey values from different CBCT examination may be charged with significant errors for various reasons [1,2,3,9,12,13,16] still, comparing the relative differences within one study may have clinical value [10]. Conscious evaluation of numerical value of CBCT image with full awareness of this technique's limitations, is of great value.…”

“…Another opportunity is the use of relative grey values (GV) or relative values of percentage differences. The latest one is the concept of using cortical bone as a reference object for assessing relative changes of alveolar trabecular bone [10]. The relative grey values were also used in the previous study to overcome the issue of different scanning conditions where maxillary bone quality was evaluated and a modified voxel grey scale was successfully used [11].…”