In vitro accuracy of a novel registration and targeting technique for image-guided template production

The objective of this study was to evaluate the accuracy of a novel registration and targeting technique for image-guided template production (IGTP) in a preliminary phantom study.

Registration of four standard dental stone casts with integrated target pellets to the corresponding computed tomography (CT) data was performed via a vacuum mouthpiece and an external reference frame (Medical Intelligence GmbH, Germany). Using the Treon navigation system (Medtronic Inc., Minneapolis, MN, USA) a surgical path with the entry in the centre of the dental crown and the target in the centre of the target pellet was planned on the CT data. An aiming device was adjusted according to the planned trajectory and guided drillings into the dental stone casts. The accuracy was evaluated on postoperative 3D-CT data.

The mean fiducial registration error as given by the registration software was 0.4 mm. One hundred and twelve navigated drillings showed a mean accuracy [xy] of 0.42+/-0.26 mm (maximum 1 mm). For the z-axis, a mean accuracy [z] of 0.25+/-0.12 mm (maximum 0.6 mm) was found.

Comparing the presented registration technique to existing registration methods in IGTP and burr tracking, no radiographic and registration templates are needed. The procedure is easy and requires only minimal effort. Navigation-controlled drillings could be performed with an accuracy that approaches the intrinsic navigation system's accuracy, a fact that warrants its use for surgical template production. Further accuracy studies of template-guided drillings are necessary before the presented registration technique can be implemented for patient treatment.