Two key issues in image guided surgery are accurate patient-to-image registration and ongoing tracking of the patient's motion. To address these concerns, a novel device for preoperative registration and automatic tracking was designed, and the accuracy attainable with the device was evaluated in experiments with a skull and in a clinical study.
Methods
The device consists of a system of four titanium screws and four fluorescent spheres fixed to carbon bars which can be easily mounted on the maxillary dentition splint. Before surgery, CT image data of a skull with the device in place was acquired and registered in a navigation system. The rigidity and reproducibility of positioning of the device were measured in 15 repeated CT acquisitions of the skull with the device in place. The registration accuracy was compared to that obtained using micro-screw markers fixed to the maxillary alveolus. To determine the potential of the device in aiding image guided cranio-maxillofacial surgery, registration accuracy and surgical outcome were assessed.
Results
Fifteen tests were performed for CT scanning with no loosening of the splint and device. The arithmetic mean of the standard deviation (SD) ranged from 0.47 mm to 0.70 mm. When the device was used for registration, the mean deviations for the eight anatomical structures investigated ranged from 0.56 mm at the left infra-orbital foramen to 0.96 mm at the right temple. Compared with the method in which titanium screws are fixed to the maxillary alveolus, the target registration error (TRE) obtained using the new device was much less. Using this device, clinical reduction of a zygomatic-orbital-maxillary complex fracture was successfully completed with a registration discrepancy of less than 0.5 mm.
Conclusions
By successfully addressing the two key issues of image guided surgery, the device could be considered accurate and potentially useful for assisting in cranio-maxillofacial surgery.
