Effect of Head Position on Linear Cephalometric Measurement Accuracy of Cone-Beam Computed Tomography

This study aimed to assess the effect of head position on linear cephalometric measurements by cone-beam computed tomography (CBCT).

CBCT scans of four human dry skulls were obtained by NewTom 3G volume scanner with alarge (15 x15 cm)field of view in 1 centric and 18 eccentric positions: 10°, 20°, and 30° tilt (right and left), 10°, 20°, and 30° rotation (right and left), 10°, 20°, and 30° extension and 10°, 20°,and 30° flexion. The distances between the selected landmarks namely the Nasion (N), Sella (Se), anterior nasal spine (AN S), Menton (Me), Gnathion (Gn), Gonion (Go), and Condylion (Co) were measured by two observers on maximum intensity projection reconstructions using the NNT Viewer software, and compared with the actual measurements (gold standard). The inter-class correlation coefficient (ICC) and the student’s t-test were used for statistical analysis.

The mean inter-rater agreement was excellent for all head positions (ICC=96.89%). The maximum error in absolute mean measurements was 2.56 mm (P=0.03) The minimum error was for the N-Me line, which is a vertical line closest to the midline.

The greatest error was observed in 30° left ward rotation for the left CoGn linear measurement. Although this level of error may not be of clinical significance, it is suggested that clinicians acquire the scans in ideal head position to minimize distortion and errors.