Diagnosis and Quantitative Assessment of Mandibular Asymmetry Using Cbct Image Volumes

Objective: To determine if 3D shape correspondence can accurately quantify mandibularasymmetry in surgical patients. Methods: Pretreatment cone-Beam CT scans were acquiredof twenty orthognathic surgery patients with different degrees and types of facial asymmetry.The maxillofacial hard tissues were segmented and mirroring was performed for virtualsurgical planning using the CranioMaxilloFacial Application software. Mirrored surgicalmodels were superimposed on the actual patient models using two different approaches: (1)mirroring on the midsagittal plane; and (2) mirroring on an arbitrary plane with registrationon the cranial base. Different amounts of additional mandibular asymmetry in the threeplanes of space were simulated by known amounts. For both mirroring methods, SPHARMshape correspondence was used to detect and quantify simulated asymmetries. ResultsSPHARM-shape correspondence accurately quantified different types and degrees ofvirtually simulated facial asymmetry. The probabilities for all 6 degrees of freedom ( rotationand translation) that the difference between asymmetry measurements and the known virtually simulated value is less than 0.5mm was very good for both mirroring techniques