Oral and maxillofacial radiology
Accuracy of segmentation of tooth structures using 3 different CBCT machines

https://doi.org/10.1016/j.oooo.2016.09.005Get rights and content

Objective

The aim of this study was to evaluate the volumetric accuracy and reliability of cone beam computed tomography (CBCT)-based tooth segmentation using 4 different CBCT exposure protocols.

Methods

Two dry, intact adult human mandibles of unknown gender were scanned using 4 different CBCT exposure protocols (3 CBCT systems). The available mandibular premolars (3 per mandible) were segmented, resulting in a total of 24 segmented teeth. To assess the accuracy of the segmented teeth, volumetric and morphologic differences between the real anatomic teeth and the reconstructed images were evaluated both physically and using a high-resolution micro-computed tomography system.

Results

Results revealed a high accuracy of CBCT reconstructed images when comparing volumetric measures of CBCT-based segmented premolars to physical measurements of corresponding physical teeth. Volumetric differences were below 2%. Morphologic differences using the segmented model and the corresponding micro-computed tomography scans of the physical teeth indicated that when inaccuracies occurred, they were at the apical and coronal parts of the tooth.

Conclusion

Based on these results, CBCT can be used as a tool for segmentation and pretherapeutic planning procedures.

Section snippets

Study sample and collection

This study was carried out on 2 dry, intact adult human mandibles of unknown gender collected from the Department of Anatomy at KU Leuven. Ethical review board approval was obtained (ML9535/ML9248, ERB University Hospitals Leuven).

Image acquisition (cone beam computed tomography, micro-computed tomography)

The mandibles were placed on a plastic tray with copper filters of 0.5 mm in front of the X-ray beam source to simulate soft tissue and to reduce X-ray beam-hardening effects.15 Both dry dentate mandibles were scanned using 3 different CBCT machines (Table I):

Results

The volume measurements of the μCT revealed a strong positive correlation with those of the 4 CBCT protocols and with the physical measurements determined using the Archimedes principle (r > 0.90) when evaluated using the Pearson correlation (Table II).

The mean absolute difference in percentage between physical measurements determined using the Archimedes principle and CBCT volume measurements was calculated using the Bland-Altman method and was found to be 1.9% with Accuitomo 170 180°

Discussion

When looking at the future of 3-D printed medical tools and replicas as a support for clinical diagnosis, planning, and treatment, it is of utmost importance to assess the accuracy of the virtual 3-D model obtained after segmentation. Since the CBCT data sets can be obtained from different scanners or scanning protocols, the present study assessed the accuracy and robustness of the obtained virtual 3-D models.

Volumetric measurements were made using the Archimedes principle, given its

Conclusion

In the present study, results reveal that all tested CBCT protocols provided high accuracy for tooth segmentation compared with anatomic tooth morphology. Therefore, CBCT-segmented teeth can be recommended as a tool for diagnostic and pretherapeutic planning procedures.

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