Accuracy of CBCT Alveolar Bone Measurements Using Multiple Acquisition Parameters

Objective: Cone-beam computed tomography (CBCT) imaging has expanded the potential to analyze alveolar bone morphology in 3 dimensions, but accuracy of the technique has yet to be well defined. To investigate the accuracy and reliability of CBCT measurements, buccal alveolar bone height (BBH) and thickness (BBT) were assessed using 2 acquisition settings.

Method: 12 embalmed human cadaver heads were scanned twice with an i-CAT® 17-19 unit (Imaging Sciences International, Hatfield, PA), once (setting A) using 0.2 mm voxel-size, 26.9 s scan, and 360º revolution, and again (setting B) using 0.3 mm, 4.8 s, and 180º. BBH and BBT measurements associated with 65 teeth were made at standardized locations in radiographic sections consistently oriented through use of a detailed protocol. Each measurement was repeated at 3 separate occasions. Direct measurements were also made using dissection. Measurements made from the 2 settings were compared by two-tailed t-tests, and agreement was assessed by concordance correlation coefficients (CCC). 

Result: Mean absolute differences in measurements for setting A were BBH 0.17± 0.12 mm and BBT 0.10 ± 0.07 mm, and for setting B were BBH 0.41±0.32 mm and BBT 0.12±0.11 mm. Comparing the settings, t-tests showed no statistical differences for BBH or BBT measurements. With either setting, neither parameter demonstrated an under- or over-estimation tendency.  Agreement between the measurement methods compared to direct measurement was high, although agreement was higher for BBH than BBT as demonstrated by CCC (BBH: A=0.99, B=0.97 vs. BBT: A=0.94, B=0.88).

Conclusion: Using multiple voxel sizes and scan times, CBCT can be used to accurately and reliably assess BBH and BBT with repeated measurements. Compared to the longer scan times, the similarity in results with the reduced scan time and hence reduced effective radiation dose favors use of the shorter scans, unless a purpose for higher resolution imaging can be defined.