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Application of cone beam computed tomography in facial imaging science

By Zacharias Fourie


In Chapter 1 the influence of facial imaging on the study of facial morphology and its developmental changes over time are discussed. This is important to diagnose malformations, to study normal and abnormal growth and to differentiate between the results of treatment and growth. The two main methods to study and record facial imaging are cephalometry and anthropometry. Cephalometrics is the scientific study of the measurements of the head's size and proportion while facial anthropometrics is the physical measurement of the human face and its parts. Several competing methods are available for capturing and quantifying craniofacial morphology. These include traditional methods, such as direct anthropometry, 2D photogrammetry and 2D cephalometry. There are several limitations to these direct and 2D imaging methods. 3D imaging on the other hand is an innovative approach in the field of facial imaging that in a very short time has found a considerable number of applications throughout the medical, dental and forensic sciences. 3D reconstructed images can provide precise and detailed information for the diagnosis of craniofacial structural problems, enhancing the specialist's perception and facilitating a more efficient treatment planning, thus making them preferable to the conventional 2D modalities. Because of the accuracy, CBCT images are powerful tools for evaluation of craniofacial morphology. CBCT can be used in clinical practice and craniofacial research in many ways. The factors influencing the quality and accuracy of a 3D model derived from a CBCT model can be divided into 3 main categories. The first are the limitation in CBCT system itself or scanner related factors such as different CBCT scanners, Field of View (FoV), artifacts and voxel size. The second are patient or subject related factors like patient position or natural head position and metal artifacts. The third are operator related factors, including segmentation process and the operator self. In Chapter 2 the geometric accuracy of 3D surface models from two segmentation protocols were assessed. We had the unique opportunity in this study of first using fresh cadaver heads and then the same skulls after maceration and no artificial media was therefore needed to simulate soft tissue. There was a clear difference between the accuracy of the commercial segmentation (CS) and doctor's segmentation (DC) models if compared to the laser surface scans (LSS) as the gold standard. Overall, the CS models resembled more closely the LSS models than the DS models.

Topics: Proefschriften (vorm), Onderkaak; Segmentering; Craniometrie; Metingen; Gelaat; Computertomografie; radiologie; tandheelkunde ;
Year: 2011
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