• Rüdiger Marmulla and Joachim Mühling.
• Department of Cranio-Maxillofacial Surgery, University of Heidelberg, Heidelberg, Germany. Ruediger.Marmulla@med.uni-heidelberg.de
• J. Oral Maxillofac. Surg. 2006 Mar 1; 64 (3): 466-70.

PurposeMotion artifacts can significantly deteriorate the precision of a computer-assisted surgical intervention because they destroy the isometric representation of tomographic pictures. In the context of a study, the influence of typical motion artifacts on the precision of markerless laser registration in image-guided oral and maxillofacial surgery was analyzed, and quality factors for evaluation of the isometry of a computed tomography (CT) dataset were determined.Patients And MethodsTwenty patients underwent markerless registration, the precision being determined by means of intraoral evaluation markers. Then the 20 CT datasets were used for simulation of a typical motion artifact. The precision of the overlay of the dataset was checked again on the navigation workstation, in absence of the patient. The navigation system used was the Surgical Segment Navigator SSN++ (University of Heidelberg, Heidelberg, Germany).ResultsThe motion artifacts reduced the average patient registration from 1 to 4 mm. Quality factors for the isometry of a CT dataset were: the volume enclosed between the soft tissue mantles of the preoperative CT dataset and the intraoperative laser scan dataset, as well as the orientation of the normal vectors on the 3-dimensional reconstruction of the CT dataset.ConclusionThe isometry of a CT dataset should always be checked before performance of a computer assisted surgical intervention because anisometric datasets result in inaccurate patient registration and navigation.

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