Comparison of 4 registration strategies for computer-aided maxillofacial surgery

Clinical validation of the virtual splint registration workflow for craniomaxillofacial surgery

Accurate registration is vital to transfer the virtual surgical plan during surgery. This study's goal was to present and clinically validate a virtual splint registration workflow. Ten dentate patients requiring revision surgery were included. Specific inclusion criterion for this study was the presence of at least two osteosynthesis screws on the orbital rim from a previous surgery. Dedicated orthognathic surgery software was used to fuse the maxillary dental scan with the computed tomography and generate a dental splint, which was imported into the navigation software and augmented with fiducial markers. Registration points were indicated virtually and the augmented splint was three-dimensionally printed. Intraoperatively, the splint was fitted on the maxillary dentition and the fiducial markers were used for registration. Accuracy of the registration procedure was quantified by calculating the difference between the landmarks acquired by indicating the pre-existing osteosynthesis material with the navigation pointer and in the virtual planning software. After acquisition of the landmarks, the screws were removed and surgery proceeded according to plan. A median target registration error of 1.53 mm was found. The advantages of the virtual splint registration workflow are that it does not require extensive computer-aided design skills or repeated preoperative imaging, and is non-invasive.

Noctopus: a novel device and method for patient registration and navigation in image-guided cranial surgery

PURPOSE

A patient registration and real-time surgical navigation system and a novel device and method (Noctopus) is presented. With any tracking system technology and a patient/target-specific registration marker configuration, submillimetric target registration error (TRE), high-precise application accuracy for single or multiple anatomical targets in image-guided neurosurgery or ENT surgery is realized.

METHODS

The system utilizes the advantages of marker-based registration technique and allows to perform automatized patient registration using on the device attached and with patient scanned four fiducial markers. The best possible sensor/marker positions around the patient's head are determined for single or multiple region(s) of interest (target/s) in the anatomy. Once brought at the predetermined positions the device can be operated with any tracking system for registration purposes.

RESULTS

Targeting accuracy was evaluated quantitatively at various target positions on a phantom skull. The target registration error (TRE) was measured on individual targets using an electromagnetic tracking system. The overall averaged TRE was 0.22 ± 0.08 mm for intraoperative measurements.

CONCLUSION

An automatized patient registration system using optimized patient-/target-specific marker configurations is proposed. High-precision and user-error-free intraoperative surgical navigation with minimum number of registration markers and sensors is realized. The targeting accuracy is significantly improved in minimally invasive neurosurgical and ENT interventions.

Comparison of the accuracy of dynamic navigation and the free hand approaches in the placement of pterygoid implants in the completely edentulous maxilla: An in vitro study

Background/purpose

Pterygoid implant is a promising solution for patients with a partially or fully edentulous atrophic maxilla. However, whether dynamic navigation system will improve the accuracy of pterygoid implant surgery is still unknown. This study aimed to compare the accuracy of dynamic navigation and free-hand approaches in pterygoid implant placement in completely edentulous maxilla models.

Materials and methods

Twenty three-dimensional (3D)-printed edentulous maxilla models were assigned to two groups: the dynamic navigation system group and the free-hand group. Two pterygoid implants were planned in the bilateral pterygomaxillary area and then placed in each model. The entry, exit and angle deviations of the pterygoid implants were measured after pre- and post-operative cone-beam CT (CBCT) image fusion. Student's t test and Mann-Whitney U test were used. A P value < 0.05 was considered statistically significant.

Results

A total of 40 pterygoid implants were placed in 20 models. The comparison deviation of the dynamic navigation group and the free-hand group showed a mean (±SD) entry deviation of 0.93 ± 0.46 mm vs. 2.28 ± 1.08 mm (P < 0.001), an exit deviation of 1.37 ± 0.52 mm vs. 3.14 ± 1.82 mm (P < 0.001), and an angle deviation of 2.41 ± 1.24° vs. 10.13 ± 4.68° (P < 0.001). There was no significant difference in the accuracy with regard to the side factors between the navigation group and the free-hand group.

Conclusion

The dynamic navigation system has higher accuracy for pterygoid implant placement in a complete edentulous maxilla than the free-hand approach.

Accuracy and Efficiency of Endodontic Microsurgery Assisted by Dynamic Navigation Based on Two Different Registration Methods: An In Vitro Study

INTRODUCTION

This study aimed to compare the accuracy and efficiency of dynamic navigation-assisted endodontic microsurgery (DN-EMS) using two different registration methods.

METHODS

Three-dimensional-printed jaw models, including 40 teeth, were divided into two groups (n = 20). Cone-beam computed tomography images of all teeth were scanned under the same exposing parameters. An endodontic dynamic navigation system (DHC-ENDO1) was used to plan the drilling paths. Dynamic navigation-assisted endodontic microsurgery (DN-EMS) was performed using either U-shaped tube (UT) or tooth cusp (TC) registration method. The accuracy was determined by platform deviation, end deviation, angular deviation, resection angle, and resection length deviation. The registration efficiency was defined as the time required to complete the registration procedure. Osteotomy volume of each resection was calculated by Mimics 21.0. Statistical analyses were performed using IBM SPSS Statistics 24.0. Comparisons between groups were performed using the independent sample t test or Mann-Whitney U test. P < .05 was adopted as significant difference.

RESULTS

The UT group was significantly more accurate in terms of mean platform deviation, end deviation, angular deviation, and resection angle (P < .05). Resection length deviation did not differ significantly between the registration groups. The UT group was significantly more efficient than the TC group (P < .05). No significant differences were found in the osteotomy volumes between the two groups.

CONCLUSIONS

In the model-based surgical simulation comparison, DN-EMS based on UT registration is more accurate and efficient than the TC method but requires an additional registration device. TC technique may be a reasonable alternative to UT registration in certain clinical tasks.

The accuracy and learning curves of active and passive dynamic navigation-guided dental implant surgery: An in vitro study

OBJECTIVES

Infrared dynamic navigation principles can be categorized into active and passive navigation systems based on whether the surgical instruments can emit or only reflect light, respectively. This in vitro study aimed to compare the accuracy of implant placement and the learning curves of both active and passive dynamic navigation systems using different registration methods.

METHODS

Implants (n=704) were placed in 64 sets of models and divided into active (Yizhime, DCARER, Suzhou, China) and passive (Iris-Clinic, EPED, Kaohsiung, China) dynamic navigation groups. Both marker point-based registration (M-PBR) and feature point-based registration (F-PBR) were employed by two groups mentioned above. Based on preoperative and postoperative cone-beam computed tomography imaging, the coronal, midpoint, apical, and angular deviations were analyzed from 2D and 3D views. The operation time was recorded for each group.

RESULTS

The active dynamic navigation group exhibited significantly greater accuracy than the passive dynamic navigation group for outcome variables (angular deviation, 4.13 ± 2.39° and 4.62 ± 3.32°; coronal global deviation, 1.48 ± 0.60 and 1.86 ± 1.12 mm; apical global deviation, 1.75 ± 0.81 and 2.20 ± 1.68 mm, respectively). Significant interaction effects were observed for both registration methods and four quadrants with different dynamic navigation systems. Learning curves for the two dynamic navigation groups approached each other after 12 procedures, and finally converged after 27 procedures.

CONCLUSIONS

The accuracy of active dynamic navigation system was superior to that of passive dynamic navigation system. Different combinations of dynamic navigation systems, registration methods, and implanted quadrants displayed various interactions.

CLINICAL SIGNIFICANCE

Our findings could provide guidance for surgeons in choosing an appropriate navigation system use in various implant surgeries. Furthermore, the time required by surgeons to master the technique was calculated for reference. Nevertheless, there are certain limitations to this in vitro study, and therefore further research is required.

Accuracy evaluation of 3D-printed noninvasive adhesive marker for dynamic navigation implant surgery in a maxillary edentulous model: An in vitro study

Dynamic computer-aided implant surgery (DCAIS) can improve dental implantation accuracy and reduce surgical risks. In the registration procedure of DCAIS, the type and the number of registration markers significantly impact the accuracy of DCAIS. One problem of DCAIS in clinical application is that only invasive screw markers can be used for implantation in edentulous patients. It could cause additional trauma, scar formation and usually increase patient discomfort. In this experiment, a personalized 3D-printed edentulous maxillary model was used for simulating clinical situations, and a 3D-printed noninvasive adhesive marker (3D-PNAM) was designed to figure out the above problem. In this research, six target screws were implanted into the model's maxillary alveolar ridge as targets for accuracy analysis. This study used target registration error (TRE) as an index to evaluate the accuracy of invasive screw makers and noninvasive adhesive markers. Results showed that 3D-PNAMs had the same accuracy as screw markers, and placing at least six registration markers in the maxilla was needed for good registration accuracy. The registration markers should be further improved and designed according to application areas' clinical needs and anatomical characteristics in future clinical studies.

Free-Hand versus Surgical Guide Implant Placement

One of the most key areas of dentistry is dental implant surgery. The use of digital equipment and software in dentistry has developed considerably in recent years compared to other fields of medicine. Since examining the advantages and disadvantages of each approach, along with case studies, can help physicians make informed decisions, this review study aims to raise the awareness of dentists to make easier decisions about using guided or free-hand surgery. When planning for a dental implant, one of the most challenging questions that doctors face is which method to use (guided surgery or free-hand). Choosing the right method, such as other clinical considerations, will depend on the individual circumstances of each patient and the preference of the treating physician. Free-hand surgery is a cost-effective method in which the flap is reflected, and, according to the doctor's diagnostic information, an implant is placed, which in many cases is a useful method. Guided surgery has the highest level of accuracy and control, in which osteotomy is designed and printed through a digital surgery guide, and depending on the complexity of the case and the patient's anatomy, it has a higher level of value than free surgery. The surgical guide helps the surgeon make the implant surgery more accurate, safer, simpler, at a lower cost, and in less time. In fact, there are patterns that convey information about the position of the tooth to the dentist before the implant is placed.

Reliability and accuracy of dynamic navigation for zygomatic implant placement

Objectives

To assess the accuracy of a real‐time dynamic navigation system applied in zygomatic implant (ZI) surgery and summarize device‐related negative events and their management.

Material and methods

Patients who presented with severely maxillary atrophy or maxillary defects and received dynamic navigation‐supported ZI surgery were included. The deviations of entry, exit, and angle were measured after image data fusion. A linear mixed‐effects model was used. Statistical significance was defined as p < .05. Device‐related negative events and their management were also recorded and analyzed.

Results

Two hundred and thirty‐one zygomatic implants (ZIs) with navigation‐guided placement were planned in 74 consecutive patients between Jan 2015 and Aug 2020. Among them, 71 patients with 221 ZIs received navigation‐guided surgery finally. The deviations in entry, exit, and angle were 1.57 ± 0.71 mm, 2.1 ± 0.94 mm and 2.68 ± 1.25 degrees, respectively. Significant differences were found in entry and exit deviation according to the number of ZIs in the zygomata (p = .03 and .00, respectively). Patients with atrophic maxillary or maxillary defects showed a significant difference in exit deviation (p = .01). A total of 28 device‐related negative events occurred, and one resulted in 2 ZI failures due to implant malposition. The overall survival rate of ZIs was 98.64%, and the mean follow‐up time was 24.11 months (Standard Deviation [SD]: 12.62).

Conclusions

The navigation‐supported ZI implantation is an accurate and reliable surgical approach. However, relevant technical negative events in the navigation process are worthy of attention.

Randomized Controlled Clinical Trial to Assess the Utility of Computer-Aided Intraoperative Navigation in Bimaxillary Orthognathic Surgery

ABSTRACT

Accurate application of the preoperative surgical plan in actual surgical settings is of paramount importance in orthognathic surgery. This randomized controlled clinical trial aimed to evaluate the accuracy of computer-aided intraoperative navigation (Ci-Navi) compared with that of conventional navigation methods in bimaxillary orthognathic surgery. Fifty-two patients were randomly divided into 2 groups. Group A (n = 26) patients underwent surgery assisted with Ci-Navi and group B (n = 26) patients underwent surgery assisted with conventional intraoperative navigation methods. During the operation, after LeFort I osteotomy, the mobile maxilla was repositioned to the designated position either using assistance from real-time Ci-Navi (group A) or using an intermediate splint (group B). Intra- and intergroup linear and angular differences between preoperative planning and postoperative outcomes were calculated. In group A, the overall mean linear difference was 0.79 mm (0.62 mm for the maxilla and 0.88 mm for the mandible) and the overall mean angular difference was 1.20°. In 23 cases, the difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm. In group B, the overall mean linear difference was 1.98 mm (1.76 mm for the maxilla and 2.02 mm for the mandible) and the overall mean angular difference was 2.08°. The difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm in 15 cases. This study demonstrates the utility of Ci-Navi is superior to the conventional methods in aiding the accurate repositioning of bony segments in bimaxillary orthognathic surgery.

A Novel Precise Optical Navigation System for Craniomaxillofacial Surgery Registered With an Occlusal Splint

BACKGROUND

An augmented reality tool allows visual tracking of real anatomical structures and superimposing virtual images, so it can be used for navigation of important structures during surgery.

OBJECTIVES

The authors have developed a new occlusal splint-based optical navigation system for craniomaxillofacial surgery. In this study, the authors aim to measure the accuracy of the system and further analyze the main factors influencing precision.

METHODS

Ten beagle dogs were selected and a three-dimensional model was established through computed tomography scanning, dental model making, and laser scanning, and then registration was performed according to the tooth marking points. The bilateral mandibular osteotomy was performed on Beagle dogs under navigation system based on the occlusal splint. The left side was taken to compare the deviation between the preoperative plan and the surgical results, and the accuracy of distance and angle and the stability of the system were analyzed.

RESULTS

The average position deviation between the preoperative design and intraoperative navigation was: 0.01 ± 0.73 mm on the lateral height of the mandibular ramus, 0.26 ± 0.57 mm on the inner height of the mandibular ramus, and 0.20 ± 0.51 mm on the osteotomy length. The average angle deviation is 0.94° ± 1.38° on the angle between the mandibular osteotomy plane and ramus plane and 0.66° ± 0.97° on the angle of the retained mandibular angle. And most of the data showed good consistency.

CONCLUSIONS

In summary, the accuracy of the system can meet clinical requirements and can be used as a useful tool to improve the accuracy of craniomaxillofacial surgery.

Updates in Management of Craniomaxillofacial Gunshot Wounds and Reconstruction of the Mandible

This article includes updates in the management of mandibular trauma and reconstruction as they relate to maxillomandibular fixation screws, custom hardware, virtual surgical planning, and protocols for use of computer-aided surgery and navigation when managing composite defects from gunshot injuries to the face.

A proof-of-concept augmented reality system in oral and maxillofacial surgery

BACKGROUND

The advent of digital medical imaging, medical image analysis and computer vision has opened the surgeon horizons with the possibility to add virtual information to the real operative field. For oral and maxillofacial surgeons, overlaying anatomical structures to protect (such as teeth, sinus floors, inferior and superior alveolar nerves) or to remove (such as cysts, tumours, impacted teeth) presents a real clinical interest.

MATERIAL AND METHODS

Through this work, we propose a proof-of-concept markerless augmented reality system for oral and maxillofacial surgery, where a virtual scene is generated preoperatively and mixed with reality to reveal the location of hidden anatomical structures intraoperatively. We devised a computer software to process still video frames of the operating field and to display them on the operating room screens.

RESULTS

Firstly, we give a description of the proposed system, where virtuality aligns with reality without artificial markers. The dental occlusion plan analysis and cusps detection allow us to initialise the alignment process. Secondly, we validate the feasibility with an experimental approach on a 3D printed jaw phantom and an ex-vivo pig jaw. Thirdly, we evaluate the potential clinical benefit on a patient.

CONCLUSION

this proof-of-concept highlights the feasibility and the interest of augmented reality for hidden anatomical structures visualisation without artificial markers.

Asymmetrical surface scanning registration for image-guided otologic surgery: A phantom study

OBJECTIVE

To develop a registration procedure to achieve a higher degree of registration accuracy in image-guided otological surgery, paying particular attention to the registration centroid.

METHODS

A head phantom was used to measure the target registration error (TRE) at measurement points at various depth from the surface of the head. The surface-matching registration was performed using a commercially available surgical navigation system. We registered the phantom using only one ear of either side (right 100% - left 0%, or right 0% - left 100%) or using both ears with variable ratios (right 75% - left 25%, right 50% - left 50%, or right 25% - left 75%).

RESULTS

The overall TRE was the smallest when registration was performed equally on both sides. However, the TRE at 20-50 mm from the surface was the smallest when the fiducial points for the registration were collected asymmetrically at a ratio of 75:25 and weighed heavier on the operating side, and this difference was statistically significant.

CONCLUSION

The accuracy of image-guided surgery can be improved by carefully planning the registration procedure without changing the procedure itself. Accurate image-guided surgery at the middle and inner ear was achieved using 75% of the point cloud for the operating side and 25% of that for the opposite side for the registration.

Development of a Mixed Reality Platform for Lateral Skull Base Anatomy

OBJECTIVES

A mixed reality (MR) headset that enables three-dimensional (3D) visualization of interactive holograms anchored to specific points in physical space was developed for use with lateral skull base anatomy. The objectives of this study are to: 1) develop an augmented reality platform using the headset for visualization of temporal bone structures, and 2) measure the accuracy of the platform as an image guidance system.

METHODS

A combination of semiautomatic and manual segmentation was used to generate 3D reconstructions of soft tissue and bony anatomy of cadaver heads and temporal bones from 2D computed tomography images. A Mixed-Reality platform was developed using C# programming to generate interactive 3D holograms that could be displayed in the HoloLens headset. Accuracy of visual surface registration was determined by target registration error between seven predefined points on a 3D holographic skull and 3D printed model.

RESULTS

Interactive 3D holograms of soft tissue, bony anatomy, and internal ear structures of cadaveric models were generated and visualized in the MR headset. Software user interface was developed to allow for user control of the virtual images through gaze, voice, and gesture commands. Visual surface point matching registration was used to align and anchor holograms to physical objects. The average target registration error of our system was 5.76 mm ± 0.54.

CONCLUSION

In this article, we demonstrate that an MR headset can be applied to display interactive 3D anatomic structures of the temporal bone that can be overlaid on physical models. This technology has the potential to be used as an image guidance tool during anatomic dissection and lateral skull base surgery.

A novel approach to skull-base and orbital osteotomies through virtual planning and navigation

OBJECTIVE

Computer-assisted planning of osteotomy lines, coupled with navigation-guided performance of planned osteotomies, is a highly innovative approach to skull-base and orbital surgery. The aim of this pilot study is to provide an assessment of the accuracy of this novel approach in guiding the correct positioning of osteotomy lines in frontal, temporal, and orbital regions, defining the agreement between the spatial position of the planned and performed osteotomies.

METHODS

Fifteen patients with orbital, frontal sinus, and lateral skull-base diseases underwent virtual surgical planning. Osteotomies to access the orbit, frontal sinus, and lateral skull base were planned on computer tomography-based three-dimensional models. The planned osteotomies were reproduced on the operating field using a navigation system. The positions of the performed and planned osteotomies were compared. The results were described as the mean positional difference between planned and performed osteotomies and as Lin's concordance coefficient, and Bland-Altman limits of agreement were also defined.

RESULTS

The overall mean difference was 0.719 mm (95% confidence interval [CI]: 0.472 to 0.965 mm). Overall, Lin's concordance coefficient was 0.997 (95% CI: 0.996 to 0.998), and overall Bland-Altman limits of agreement ranged from -1.407 to 2.844 mm. The smallest mean difference (0.587 mm, 95% CI: 0.244 to 0.931 mm) was calculated in the orbit group, whereas the highest mean difference (0.904 mm, 95% CI: 0.428 to 1.379 mm) was described in the lateral skull-base group.

CONCLUSION

This study's results support the use of this novel planning and navigation protocol for guiding osteotomy in anterior and lateral skull-base surgery, providing a clinical validation of this technique.

LEVEL OF EVIDENCE

4 Laryngoscope, 00:1-9, 2018 Laryngoscope, 129:823-831, 2019.

Probe versus microscope: a comparison of different methods for image-to-patient registration

PURPOSE

Computer-aided navigation is widely used in ENT surgery. The position of a surgical instrument is shown in the CT/MR images of the patient and can thus be a good support for the surgeon. The accuracy is highly dependent on the registration done prior to surgery. A microscope and a probe can both be used for registration and navigation, depending on the surgical intervention. A navigation system typically only reports the fiducial registration error after paired-point registration. However, the target registration error (TRE)-a measurement for the accuracy in the surgical area-is much more relevant. The aim of this work was to compare the performance of a microscope relative to a conventional probe-based approach with different registration methods.

METHODS

In this study, optical tracking was used to register a plastic skull to its preoperative CT images with paired-point registration. Anatomical landmarks and skin-affixed markers were used as fiducials and targets. With both microscope and probe, four different registration methods were evaluated based on their TREs at 10 targets. For half of the experiments, a surface registration and/or external fiducials were used additionally to paired-point registration to study their influence to accuracy.

RESULTS

Overall, probe registration leads to a smaller TRE ([Formula: see text]) than registration with a microscope ([Formula: see text]). Additional surface registration does not result in better accuracy of navigation for microscope and probe. The lowest mean TRE for both pointers can be achieved with paired-point registration only and radiolucent markers.

CONCLUSION

Our experiments showed that a probe used for registration and navigation achieves lower TREs compared using a microscope. Neither additional surface registration nor additional fiducials on an external reference element are necessary for improved accuracy of navigated ENT surgery on a plastic skull.

Freehand Versus Guided Surgery: Factors Influencing Accuracy of Dental Implant Placement

INTRODUCTION

Patient anatomy, practitioner experience, and surgical approach are all factors that influence implant accuracy. However, the relative importance of each factor is poorly understood. The present study aimed to identify which factors most critically determine implant accuracy to aid the practitioner in case selection for guided versus freehand surgery.

METHODS

One practitioner's ideal implant angulation and position was compared with his achieved position radiographically for 450 implants placed using a conventional freehand method. The relative contribution of 11 demographic, anatomical, and surgical factors to the accuracy of implant placement was systematically quantified.

DISCUSSION

The most important predictors of angulation and position accuracy were the number of adjacent implants placed and the tooth-borne status of the site. Immediate placement also significantly increased position accuracy, whereas cases with narrow sites were significantly more accurate in angulation. Accuracy also improved with the practitioner's experience.

CONCLUSION

These results suggest tooth-borne, single-implant cases performed later in the practitioner's experience are most appropriate for freehand placement, whereas guided surgery should be considered to improve accuracy for multiple-implant cases in edentulous or partially edentulous sites.

Updates in Management of Craniomaxillofacial Gunshot Wounds and Reconstruction of the Mandible

This article includes updates in the management of mandibular trauma and reconstruction as they relate to maxillomandibular fixation screws, custom hardware, virtual surgical planning, and protocols for use of computer-aided surgery and navigation when managing composite defects from gunshot injuries to the face.

Navigation accuracy after automatic- and hybrid-surface registration in sinus and skull base surgery

Objective

Computer-aided-surgery in ENT surgery is mainly used for sinus surgery but navigation accuracy still reaches its limits for skull base procedures. Knowledge of navigation accuracy in distinct anatomical regions is therefore mandatory. This study examined whether navigation accuracy can be improved in specific anatomical localizations by using hybrid registration technique.

Study design

Experimental phantom study.

Setting

Operating room.

Subjects and methods

The gold standard of screw registration was compared with automatic LED-mask-registration alone, and in combination with additional surface matching. 3D-printer-based skull models with individual fabricated silicone skin were used for the experiments. Overall navigation accuracy considering 26 target fiducials distributed over each skull was measured as well as the accuracy on selected anatomic localizations.

Results

Overall navigation accuracy was <1.0 mm in all cases, showing the significantly lowest values after screw registration (0.66 ± 0.08 mm), followed by hybrid registration (0.83± 0.08 mm), and sole mask registration (0.92 ± 0.13 mm).On selected anatomic localizations screw registration was significantly superior on the sphenoid sinus and on the internal auditory canal. However, mask registration showed significantly better accuracy results on the midface. Navigation accuracy on skull base localizations could be significantly improved by the combination of mask registration and additional surface matching.

Conclusion

Overall navigation accuracy gives no sufficient information regarding navigation accuracy in a distinct anatomic area. The non-invasive LED-mask-registration proved to be an alternative in clinical routine showing best accuracy results on the midface. For challenging skull base procedures a hybrid registration technique is recommendable which improves navigation accuracy significantly in this operating field. Invasive registration procedures are reserved for selected challenging skull base operations where the required high precision warrants the invasiveness.

Coffee: the key to safer image-guided surgery-a granular jamming cap for non-invasive, rigid fixation of fiducial markers to the patient

PURPOSE

Accurate image guidance requires a rigid connection between tracked fiducial markers and the patient, which cannot be guaranteed by current non-invasive attachment techniques. We propose a new granular jamming approach to firmly, yet non-invasively, connect fiducials to the patient.

METHODS

Our granular jamming cap surrounds the head and conforms to the contours of the patient's skull. When a vacuum is drawn, the device solidifies in a manner conceptually like a vacuum-packed bag of ground coffee, providing a rigid structure that can firmly hold fiducial markers to the patient's skull. By using the new Polaris Krios optical tracker, we can also use more fiducials in advantageous configurations to reduce registration error.

RESULTS

We tested our new approach against a clinically used headband-based fiducial fixation device under perturbations that could reasonably be expected to occur in a real-world operating room. In bump testing, we found that the granular jamming cap reduced average TRE at the skull base from 2.29 to 0.56 mm and maximum TRE at the same point from 7.65 to 1.30 mm. Clinically significant TRE reductions were also observed in head repositioning and static force testing experiments.

CONCLUSION

The granular jamming cap concept increases the robustness and accuracy of image-guided sinus and skull base surgery by more firmly attaching fiducial markers to the patient's skull.

A novel augmented reality system for displaying inferior alveolar nerve bundles in maxillofacial surgery

Augmented reality systems can combine virtual images with a real environment to ensure accurate surgery with lower risk. This study aimed to develop a novel registration and tracking technique to establish a navigation system based on augmented reality for maxillofacial surgery. Specifically, a virtual image is reconstructed from CT data using 3D software. The real environment is tracked by the augmented reality (AR) software. The novel registration strategy that we created uses an occlusal splint compounded with a fiducial marker (OSM) to establish a relationship between the virtual image and the real object. After the fiducial marker is recognized, the virtual image is superimposed onto the real environment, forming the “integrated image” on semi-transparent glass. Via the registration process, the integral image, which combines the virtual image with the real scene, is successfully presented on the semi-transparent helmet. The position error of this navigation system is 0.96 ± 0.51 mm. This augmented reality system was applied in the clinic and good surgical outcomes were obtained. The augmented reality system that we established for maxillofacial surgery has the advantages of easy manipulation and high accuracy, which can improve surgical outcomes. Thus, this system exhibits significant potential in clinical applications.

Registration using 3D-printed rigid templates outperforms manually scanned surface matching in image-guided temporal bone surgery

PURPOSE

Image-guided surgery (IGS) for otological procedures requires minimal invasiveness and a high degree of accuracy. We have recently developed a noninvasive registration method, the Surface Template-Assisted Marker Positioning (STAMP) method, which uses a rigid template of the surface of the temporal bone. However, the STAMP method is not applicable when the bony surface is not exposed, such as in endoscopic surgery. Thus, we extended our research to apply the STAMP method onto the skin and tested its feasibility in this study.

METHODS

We designed a phantom made of a rigid box and soft material for the study. The target registration error (TRE) was measured at preset measuring points in the phantom. We modified the STAMP method to be applicable for use on the skin around the ears (S-STAMP). The same phantom was also registered using the conventional, manually scanned surface matching method. We compared the TRE after the different registration methods.

RESULTS

The TRE after the S-STAMP registration method was significantly smaller than that of the conventional surface matching method at all error measurement points in the phantom. However, the TRE after the S-STAMP registration method was significantly larger than that of paired point registration using invasive fiducial markers.

CONCLUSIONS

The S-STAMP method using a rigid template on the soft surface yields a significantly smaller TRE than that of conventional, manually scanned surface matching registration. This strategy provides an alternative option to improve the accuracy of IGS without loading patients with additional invasive procedures.

Prospects and limitations of different registration modalities in electromagnetic ENT navigation

The present study examined electromagnetic tracking technology for ENT navigation. Five different registration modalities were compared and navigation accuracy was assessed. Four skull models were individually fabricated with a three-dimensional printer, based on patients' computer tomography datasets. Individual silicone masks were fitted for skin and soft tissue simulation. Five registration modalities were examined: (1) invasive marker, (2) automatic, (3) surface matching (AccuMatch), (4) anatomic landmarks, and (5) oral splint registration. Overall navigation accuracy and accuracy on selected anatomic locations were assessed by targeting 26 titanium screws previously placed over the skull. Overall navigation accuracy differed significantly between all registration modalities. The target registration error was 0.94 ± 0.06 mm (quadratic mean ± standard deviation) for the invasive marker registration, 1.41 ± 0.04 mm for the automatic registration, 1.59 ± 0.14 mm for the surface matching registration, and 5.15 ± 0.66 mm (four landmarks) and 4.37 ± 0.73 mm (five landmarks) for the anatomic landmark registration. Oral splint registration proved itself to be inapplicable to this navigation system. Invasive marker registration was superior on most selected anatomic locations. However, on the ethmoid and sphenoid sinus the automatic registration process revealed significantly lower target registration error values. Only automatic and surface registration met the accuracy requirements for noninvasive registration. Particularly, the automatic image-to-world registration reaches target registration error values on the anterior skull base which are comparable with the gold standard of invasive screw registration.

Evaluation of 3 different registration techniques in image-guided bimaxillary surgery

Perioperative navigation is an upcoming tool in orthognathic surgery. This study aimed to access the feasibility of the technique and to evaluate the success rate of 3 different registration methods--facial surface registration, anatomic landmark-based registration, and template-based registration. The BrainLab navigation system (BrainLab AG, Feldkirchen, Germany) was used as an additional precision tool for 85 patients who underwent bimaxillary orthognathic surgery from February 2010 to June 2012. Eighteen cases of facial surface-based registration, 63 cases of anatomic landmark-based registration, and 8 cases of template-based registration were analyzed. The overall success rate of facial surface-based registration was 39%, which was significant lower than template-based (100%, P = 0.013) and anatomic landmark-based registration (95%, P < 0.0001). In all cases with successful registration, the further procedure of surgical navigation was performed. The concept of navigation of the maxilla during bimaxillary orthognathic surgery has been proved to be feasible. The registration process is the critical point regarding success of intraoperative navigation. Anatomic landmark-based registration is a reliable technique for image-guided bimaxillary surgery. In contrast, facial surface-based registration is highly unreliable.

Image-guided bone resection as a prospective alternative to cutting templates—A preliminary study

OBJECTIVE

To evaluate the accuracy of craniomaxillofacial resections performed with an image-guided surgical sagittal saw.

MATERIAL AND METHODS

Twenty-four craniomaxillofacial resections were performed using an image-guided sagittal saw. Surgical outcomes were compared with a preoperative virtual plan in terms of the resected bone volume, control point position and osteotomy trajectory angle. Each measurement was performed twice by two independent observers.

RESULTS

The best convergence between the planned and actual bone resection was observed for the orbital region (6.33 ± 4.04%). The smallest mean difference between the preoperative and postoperative control point positions (2.00 ± 0.66 mm) and the lowest mean angular deviation between the virtual and actual osteotomy (5.49 ± 3.17 degrees) were documented for the maxillary region. When all the performed procedures were analyzed together, mean difference between the planned and actual bone resection volumes was 9.48 ± 4.91%, mean difference between the preoperative and postoperative control point positions amounted to 2.59 ± 1.41 mm, and mean angular deviation between the planned and actual osteotomy trajectory equaled 8.21 ± 5.69 degrees.

CONCLUSION

The results of this study are encouraging but not fully satisfactory. If further improved, the hereby presented navigation technique may become a valuable supporting method for craniomaxillofacial resections.

Comparison of 3D C-arm-based registration to conventional pair-point registration regarding navigation accuracy in ENT surgery

OBJECTIVE

Navigation surgery on the skull base requires high navigation accuracy. The registration process is related to the main loss in accuracy. This study compared titanium screw registration with an inbuilt registration process of a 3-dimensional (3D) C-arm.

STUDY DESIGN

Experimental phantom study.

SETTING

Operating room.

SUBJECTS AND METHODS

Four skull models were fabricated with a 3D printer based on the patient's computed tomography (CT) data sets and fitted with an individually customized silicone skin. A 3D-isocentric C-arm fluoroscopic image intensifier system combined with a flat panel detector performed scans of petrous bones (PB) and paranasal sinuses (PS). The navigation accuracy of pair-point registration (PPR) with titanium screws was compared with C-arm-based registration.

RESULTS

Overall navigation accuracy was 1.53 ± 0.51 mm after PPR and 1.26 ± 0.12 mm after C-arm registration (P = .0259). PPR showed the best accuracy results on PS (1.28 ± 0.69 mm), followed by right PB (1.43 ± 0.52 mm) and left PB (1.74 ± 0.69 mm). A significant difference was seen only between PS and left PB (P = .0206). In contrast, C-arm registration revealed significantly lower target registration errors (TREs) on PB (0.99 ± 0.23 mm right PB, P < .0001; 1.2 ± 0.35 mm left PB, P = .0412) compared with PS. When comparing both registration modalities, C-arm registration was significantly superior on PB. With respect to specific anatomic locations, C-arm-based registration showed significantly lower TREs on the frontal and lateral skull base than PPR.

CONCLUSION

C-arm-based navigation shows higher navigation accuracy on the skull base compared with PPR. As the 3D C-arm allows real-time imaging and real-time navigation, it will be a helpful tool for skull base surgeons.

Validation of anatomical landmarks-based registration for image-guided surgery: an in-vitro study

INTRODUCTION

Perioperative navigation is a recent addition to orthognathic surgery. This study aimed to evaluate the accuracy of anatomical landmarks-based registration.

MATERIALS AND METHODS

Eighty-five holes (1.2 mm diameter) were drilled in the surface of a plastic skull model, which was then scanned using a SkyView cone beam computed tomography scanner. DICOM files were imported into BrainLab ENT 3.0.0 to make a surgical plan. Six anatomical points were selected for registration: the infraorbital foramena, the anterior nasal spine, the crown tips of the upper canines, and the mesial contact point of the upper incisors. Each registration was performed five times by two separate observers (10 times total).

RESULTS

The mean target registration error (TRE) in the anterior maxillary/zygomatic region was 0.93 ± 0.31 mm (p < 0.001 compared with other anatomical regions). The only statistically significant inter-observer difference of mean TRE was at the zygomatic arch, but was not clinically relevant.

CONCLUSION

With six anatomical landmarks used, the mean TRE was clinically acceptable in the maxillary/zygomatic region. This registration technique may be used to access occlusal changes during bimaxillary surgery, but should be used with caution in other anatomical regions of the skull because of the large TRE observed.

Official measurement protocol and accuracy results for an optical surgical navigation system (NPU)

Image-guided surgical navigation is on the rise in many different areas of modern medicine and is already an established standard in some disciplines like ear nose and throat (ENT) or maxillofacial surgery. When evaluating surgical navigation systems the absolute accuracy of the device is of major concern to the surgeon. The following work presents two different ways of measuring the accuracy of surgical navigation systems using the example of the KARL STORZ Navigation Panel Unit (NPU). According to these protocols the FDA approval of the NPU navigation system was prepared. In a first series of experiments the accuracy under realistic surgical conditions is evaluated with a phantom of a human head, which is manufactured in rapid-prototyping processes. In another series of experiments a custom registration board is used, which provides means to evaluate the accuracy under optimal conditions and also allows further measurements regarding the registration error, that are not possible with the phantom. In the experiments an accuracy of 1.44 mm ± 0.18 mm was measured in the surgical setup and 0.63 mm ± 0.07 mm under ideal conditions.

Design and accuracy evaluation of a new navigated drill system for computer assisted ENT-surgery

In this article a new navigated drill system for computer assisted ear, nose and throat (ENT) surgery is presented. The navigated drill and the microscope probe are part of a surgical navigation system for ENT-surgery. In particular, the accuracy of the new navigated drill is compared to an existing navigated drill experimentally under conditions close to the surgical workflow. For the technical accuracy experiment, the new navigated drill in combination with the new microscope probe and a particular navigated measurement board have been integrated, together with the current navigated drill, in a navigation system by a special navigation software with measuring function, based on a standard ENT navigation software. The developed navigated measurement board provided the implementation of reproducible experiments and the direct accuracy comparison of the two navigated instruments under the same conditions. Thereby, N = 15 accuracy experiments are performed with both navigated drill systems with three possible tracker positions. The distance between the planned and the touched points were calculated and compared. The average distances from the planned points to the touched points with the new navigated drill is in the left tracker position 1.10 mm, in the middle tracker position 1.14 mm and in the right tracker position 1.59 mm. In comparison to the existing drill, the new navigated drill, measured with each tracker position, is 0.62 mm more accurate.

Registration strategy using occlusal splint based on augmented reality for mandibular angle oblique split osteotomy

BACKGROUND

An augmented reality tool allows for visual tracking of real anatomic structures in superposition with volume-rendered computed tomographic or magnetic resonance imaging scans and thus can be used for navigated translocation of important structures during operation. In this feasibility study, ARToolKit was used in mandibular angle oblique split osteotomy to define the cutting planes according to an operative plan.

METHODS

We overlay the operative plan on the model of a mandible made by rapid prototyping technology, and the technology was successfully used in 15 patients. Before the operation, all patients underwent computed tomographic scan, and dental casts were prepared by surgeons. Then, surgeons make the occlusal splint according to a dental cast to fix the marker, which can be recognized by the ARToolKit. The occlusal splint and marker were transformed to three-dimensional data using a laser scanner, and a programmer that runs on a personal computer named Rapidform matches the marker and the mandible image to generate the virtual image. By this step, the virtual image describing the marker, occlusal splint, and the mandible image of the patient are integrated. During the operation, the operative plan was overlaid on the rapid prototyping model of the mandible as soon as the ARToolKit recognized the marker.

RESULTS

The technology was successfully used in 15 patients; the virtual image of the mandible and the cutting-plane both overlaid the real model of the mandible.

CONCLUSIONS

This study has reported a new and effective way for mandibular angle oblique split osteotomy, and using occlusal splint might be a powerful option for the registration of augmented reality. Augmented reality tools like ARToolKit may be helpful for control of maxillary translocation in orthognathic surgery.