Accuracy of linear intraoral measurements using cone beam CT and multidetector CT: a tale of two CTs

Abstract

Objectives: The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT.

Methods: Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated.

Results: Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (-1.35 mm; 1.82 mm) than in CBCT (-0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (-0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%).

Conclusions: CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.

Figure 1

(a) Measurements taken. IE, incisal edge; GM, gingival margin; ABR, alveolar bone ridge. (b) Representative multidetector CT scan, specimen 949

Figure 2

Orientation of the multiplanar image reformations perpendicular to the dentition, enabling one to view every assessed tooth in its buccolingual profile

Figure 3

Box and whisker plot of the differences (Diff) between the radiological (Rx) and anatomical (Anat) measurements. CBCT, cone beam CT; MDCT, multidetector CT

Figure 4

Bland–Altman plots for (a) multidetector CT (bone), (b) cone beam CT (CBCT) (bone) and (c) CBCT (soft tissue). Mean value (solid thick middle line), limits of agreement (broken lines) and 95% confidence intervals of the limits of agreement (solid thin lines) are shown. Anat, anatomical; Diff, difference; SD, standard deviation

Figure 5

Representative scan of the identical specimen (same region and same multiplanar reformatting) with typically constrained data from metal reconstruction. (a) Multidetector CT, (b) cone beam CT. Note the obvious difference in image quality

Figure 6

Lip retractor commonly used in orthodontics. This tool might be useful in cone beam CT image acquisition for gingival measurements