Several methods enabling independent repositioning of the maxilla have been introduced to reduce intraoperative errors inherent in the intermediate splint. However, the accuracy is still to be improved and a different approach without time-consuming laboratory process is needed, which can allow perioperative modification of unoptimized maxillary position. The purpose of this study is to assess the feasibility and accuracy of a robot arm combined with intraoperative image-guided navigation in orthognathic surgery. The experiments were performed on 12 full skull phantom models. After Le Fort I osteotomy, the maxillary segment was repositioned to a different target position using a robot arm and image-guided navigation and stabilized. Using the navigation and the postoperative computed tomography (CT) images, the achieved maxillary position was compared with the planned position. Although the maxilla showed mild displacement during the fixation, the mean absolute deviations from the target position were 0.16 mm, 0.18 mm, and 0.20 mm in medio-lateral, antero-posterior, and supero-inferior directions, respectively, in the intraoperative navigation. Compared with the target position using postoperative CT, the achieved maxillary position had a mean absolute deviation of less than 0.5 mm for all dimensions and the mean root mean square deviation was 0.79 mm. The results of this study suggest that the robot arm combined with the intraoperative image-guided navigation may have great potential for surgical plan transfer with the accurate repositioning of the maxilla in the orthognathic surgery.
The purpose of this study was to develop a complete digital workflow for planning, simulation, and evaluation for orthognathic surgery based on 3D digital natural head position reproduction, a cloud-based collaboration platform, and 3D landmark-based evaluation. We included 24 patients who underwent bimaxillary orthognathic surgery. Surgeons and engineers could share the massive image data immediately and conveniently and collaborate closely in surgical planning and simulation using a cloud-based platform. The digital surgical splint could be optimized for a specific patient before or after the physical fabrication of 3D printing splints through close collaboration. The surgical accuracy was evaluated comprehensively via the translational (linear) and rotational (angular) discrepancies between identical 3D landmarks on the simulation and postoperative computed tomography (CT) models. The means of the absolute linear discrepancy at eight tooth landmarks were 0.61 ± 0.55, 0.86 ± 0.68, and 1.00 ± 0.79 mm in left–right, advance–setback, and impaction–elongation directions, respectively, and 1.67 mm in the root mean square direction. The linear discrepancy in the left–right direction was significantly different from the other two directions as shown by analysis of variance (ANOVA, p < 0.05). The means of the absolute angular discrepancies were 1.43 ± 1.06°, 0.50 ± 0.31°, and 0.58 ± 0.41° in the pitch, roll, and yaw orientations, respectively. The angular discrepancy in the pitch orientation was significantly different from the other two orientations (ANOVA, p < 0.05). The complete digital workflow that we developed for orthognathic patients provides efficient and streamlined procedures for orthognathic surgery and shows high surgical accuracy with efficient image data sharing and close collaboration.
This study aimed to present a simplified and safe method to reposition the bone segment with easy identification and removing bone interference using a robot arm and image-guided navigation and to assess the accuracy for maxillary orthognathic surgery on phantom skulls. A surgical system consists of a robot arm with specialized end-effector, and image-guided navigation including the optical tracking system. The end-effector was designed to reflect the surgical procedures including identification and removal of bone interference and repositioning of the bone segment. To evaluate the handling and accuracy of this system, 10 phantom-based experiments were conducted according to four surgical plans. Mean absolute deviations at the upper central incisor were 0.10 ± 0.15 mm medio-laterally, 0.05 ± 0.07 mm antero-posteriorly, and 0.12 ± 0.15 mm supero-inferiorly. There was no significant difference in deviations between anterior and posterior regions of the maxilla. The mean root mean square deviation was 0.18 ± 0.16 mm, and ranged from 0.05 mm to 0.54 mm. The robot arm and image-guided navigation assisted surgical system would be helpful to manage bone interferences and reposition bone segments with improved accuracy. Though further technological advances are necessary, this study may provide a basis for developing clinically applicable robot assisted system for orthognathic surgery.
Energy resolved photon-counting detectors could achieve more than one spectral measurement. The goal of this study is to investigate, with experiment, the ability to decompose five materials using energy discriminating detectors and multiple discriminant analysis (MDA). A small field-of-view multi-energy CT system was built. Linear attenuation coefficient was considered as features of multiple energy CT. MDA was used to decompose five materials with six measurements of the energy dependent linear attenuation coefficients. The results of the experimental study showed that a CT system based on CdTe detectors with MDA can be used to decompose five materials.
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