Galibourg Antoine, Dumoncel Jean, Telmon Norbert, Calvet Adèle, Michetti Jérôme, Maret Delphine
1 Laboratoire Anthropologie Moléculaire et Imagerie de Synthèse, Université Paul Sabatier, Toulouse, France.
2 Faculté de Chirurgie Dentaire, Université Paul Sabatier, Centre Hospitalier Universitaire, Toulouse, France.
Dentomaxillofac Radiol. 2018 Jan;47(1):20170220. doi: 10.1259/dmfr.20170220. Epub 2017 Nov 1.
Tooth 3D automatic segmentation (AS) is being actively developed in research and clinical fields. Here, we assess the effect of automatic segmentation using a watershed-based method on the accuracy and reproducibility of 3D reconstructions in volumetric measurements by comparing it with a semi-automatic segmentation(SAS) method that has already been validated.
The study sample comprised 52 teeth, scanned with micro-CT (41 µm voxel size) and CBCT (76; 200 and 300 µm voxel size). Each tooth was segmented by AS based on a watershed method and by SAS. For all surface reconstructions, volumetric measurements were obtained and analysed statistically. Surfaces were then aligned using the SAS surfaces as the reference. The topography of the geometric discrepancies was displayed by using a colour map allowing the maximum differences to be located.
AS reconstructions showed similar tooth volumes when compared with SAS for the 41 µm voxel size. A difference in volumes was observed, and increased with the voxel size for CBCT data. The maximum differences were mainly found at the cervical margins and incisal edges but the general form was preserved.
Micro-CT, a modality used in dental research, provides data that can be segmented automatically, which is timesaving. AS with CBCT data enables the general form of the region of interest to be displayed. However, our AS method can still be used for metrically reliable measurements in the field of clinical dentistry if some manual refinements are applied.
牙齿三维自动分割（AS）在研究和临床领域正得到积极发展。在此，我们通过将基于分水岭法的自动分割与已得到验证的半自动分割（SAS）方法进行比较，评估其对体积测量中三维重建的准确性和可重复性的影响。
研究样本包括52颗牙齿，用微CT（体素大小为41µm）和CBCT（体素大小分别为76、200和300µm）进行扫描。每颗牙齿分别通过基于分水岭法的AS和SAS进行分割。对于所有表面重建，获取体积测量值并进行统计分析。然后以SAS表面为参考对齐表面。通过使用颜色图显示几何差异的地形，以便定位最大差异。
对于体素大小为41µm的数据，与SAS相比，AS重建显示出相似的牙齿体积。观察到体积存在差异，并且对于CBCT数据，该差异随体素大小增加。最大差异主要出现在颈部边缘和切缘，但总体形态得以保留。
牙科研究中使用的微CT提供了可自动分割的数据，节省时间。使用CBCT数据进行AS能够显示感兴趣区域的总体形态。然而，如果进行一些手动优化，我们的AS方法仍可用于临床牙科领域的可靠测量。
