Oral and maxillofacial radiology
Geometric accuracy of a newly developed cone-beam device for maxillofacial imaging

https://doi.org/10.1016/j.tripleo.2007.02.021Get rights and content

Objective

The aim of this study was to determine the geometric accuracy of scans obtained with a newly developed cone-beam computed tomography (CBCT) device in comparison with a multidetector row computed tomography (MDCT) scanner.

Study design

Cone-beam scans were obtained with the preretail version of a newly developed compact size device with a scan volume of 15 × 15 × 15 cm. Conventional CT scans for comparison were performed with a 6-detector row CT scanner. To determine distance accuracy, 100 measurements were performed on radiopaque markers on a dry human skull. To determine volume accuracy, 25 measurements were carried out on a geometric phantom. Commercially availables software was used for three-dimensional visualization and measurements on imaging data.

Results

Mean absolute measurement error (AME) for linear distances was 0.26 mm (±0.18 mm) for the CBCT device and 0.18 mm (±0.17 mm) for the MDCT device (P = .196 in paired t test). The average absolute percentage error (APE) was 0.98% (±0.73%) and 1.26% (±1.50%), respectively (P = .485 in paired t test). Linear regression analysis showed a positive correlation between AME and distance length (R = 0.628; P = .004) for CBCT-based measurements. Average AME in volume measurements was 1.78 mL (±0.99 mL) for the CBCT device and 1.23 mL (±0.93 mL) for the MDCT device. The average APE was 6.01% (±1.49%) and 4.42% (±1.99%), respectively.

Conclusions

The results indicate that the evaluated cone-beam device provides satisfactory information about linear distances and volumes. Multidetector row computed tomography scans proved slightly more accurate in both measurement categories. The difference may be considered as not relevant for the majority of clinical applications.

Section snippets

Imaging devices

Three-dimensional imaging data was acquired by the preretail version of a newly developed cone-beam system named GALILEOS (Sirona Dental Systems Inc., Bensheim, Germany). It consists of an x-ray generator and a two-dimensional detector aligned and mounted across from each other on a U arm. The radiation source/detector unit completes a 200° rotation around the patient’s head, acquiring 200 projected images. During the examination, the patient sits or stays in the rotation center. The position

Linear distance accuracy

Linear distance measurements revealed an average absolute error of 0.26 mm (±0.18 mm) for the CBCT scanner and of 0.18 mm (±0.17 mm) for the MDCT scanner. The paired t test showed no statistically significant difference in AME between both imaging modes (P = .196). The average APE was 0.98% (±0.73%) and 1.26% (±1.50%), respectively. There was no statistically significant difference in APE between both techniques in the paired t test (P = .485) either. Linear regression analysis showed a

Discussion

Since specialized cone-beam devices for maxillofacial imaging represent a relatively new technology, there are few studies focusing on their geometric accuracy. Lascala et al.19 performed linear measurements on 13 distances between anatomical landmarks in dry human skulls scanned with the NewTom 9000 device (Quantitative Radiology, Verona, Italy). They concluded that the real distances measured on dry skulls were always larger than those obtained from the CBCT images. However, these differences

Conclusion

The evaluated CBCT device provides satisfactory information about linear distances and volumes. Multidetector row computed tomography scans proved slightly more accurate in both measurement categories. The difference between the imaging modes was statistically not significant for linear distance estimations. At the current development stage of the CBCT machine, conventional CT technique should be preferred for accuracy-sensitive geometric measurements of large distances (>10 cm, presumed

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