Preoperative Planning Data Research Articles

Comparative analysis of the developed method of preoperative planning in primary hip arthroplasty

Aim – to conduct a comparative assessment of the accuracy of the developed method of preoperative planning for primary hip arthroplasty. Material and methods. The "Method of preoperative planning in hip arthroplasty" and special device were developed to improve the accuracy of preoperative planning and reduce the number of complications. A clinical study was conducted in the comparison groups. In the main group (50 patients), we used the proposed method in the pre-operative planning; in the control group the patients were prepared for the operation using a standard planning method. The accuracy of evaluation of implant sizes, limb length and offset were registered in the post-operative period. The preoperative planning data were compared with the results obtained. Results. The accuracy of offset estimation in the main group was higher than in the control group (T-criterion = -2.6; p = 0.01). The average difference between the estimated offset and the one obtained in the main group was 1.4±1.5 mm, in the control group it was 2.2±1.7 mm. The error in head size estimation in the main group was less than in the control group (odds ratio = 3.02). No significant differences were registered in determining the size of components of the endoprosthesis, and there were no differences in the leg length in the study groups. Conclusion. The developed method allows for improving the accuracy of preoperative planning in hip arthroplasty. The proposed device ensures the correct placement of patients when performing pelvic radiography, and also makes it easy to change it when performing this procedure.

Computer-assisted simulated workplace-based assessment in surgery: application of the universal framework of intraoperative performance within a mixed-reality simulation

ObjectivesWorkplace-based assessment (WBA) is a key requirement of competency-based medical education in postgraduate surgical education. Although simulated workplace-based assessment (SWBA) has been proposed to complement WBA, it is insufficiently adopted...

Does the fixture thread depth affect the accuracy of implant placement during fully guided immediate implant placement?: A human cadaver study.

The fixture thread depth reportedly influences the primary stability of dental implant, but its effect on the positional accuracy in immediate implant placement has not been reported previously. Fifty-six single-rooted, anterior and premolar teeth were extracted from six human cadavers, followed by installing either regular-threaded implants (RT group, N=30) or deep-threaded implants (DT group, N=26) completely relying on the surgical guide. Optical impressions taken after osteotomy and fixture installation were superimposed with the preoperative virtual planning data to measure the vertical, angular, platform and apex deviations that occurred during osteotomy and installation. While the osteotomy deviations were similar between the two groups, the angular and apex deviation of the DT group (2.67 ± 2.56°; 1.04 ± 0.49 mm, respectively) were significantly larger than those of the RT group (1.61 ± 1.04°; 0.67 ± 0.41 mm, respectively) during installation (p < .05). When the installation deviations were analysed in the anterior and premolar areas separately, the angular, platform and apex deviations of the DT group (3.05 ± 3.26°; 0.75 ± 0.32 mm; 1.08 ± 0.56 mm, respectively) were significantly larger than those of the RT group (1.56 ± 0.73°, 0.59 ± 0.28 mm; 0.62 ± 0.38 mm, respectively) in the anterior site (p < .05), whereas there was no significant intergroup difference in the premolar site. In immediate-implant surgery, using an implant with a deeper thread might increase the deviations during installation, especially in the anterior area.

Virtual Reality(VR) simulation for Oral and Maxillofacial Surgery

The aim of this study is to review the surgical application of virtual reality(VR) and augmented reality(AR) and report the cases by using virtual reality simulation and augmented reality navigation surgery. Virtual reality can provide an intuitive simulation that anyone can use easily and even if the understanding of the software is low. Virtual reality performs the operation in advance by reproducing the actual operation situation, and make the pre-operative plan. Virtual reality that makes this simulation possible, and this virtual reality-based simulation can also be used for surgical education. Additionally, from the virtual planning can be applied for making 3D printing surgical guide using exporting the pre-operative planning data. Augmented reality could be highly useful for navigation in real operation.

Soft-tissue simulation of the breast for intraoperative navigation and fusion of preoperative planning.

Computational preoperative planning offers the opportunity to reduce surgery time and patient risk. However, on soft tissues such as the breast, deviations between the preoperative and intraoperative settings largely limit the applicability of preoperative planning. In this work, we propose a high-performance accurate simulation model of the breast, to fuse preoperative information with the intraoperative deformation setting. Our simulation method encompasses three major elements: high-quality finite-element modeling (FEM), efficient handling of anatomical couplings for high-performance computation, and personalized parameter estimation from surface scans. We show the applicability of our method on two problems: 1) transforming high-quality preoperative scans to the intraoperative setting for fusion of preoperative planning data, and 2) real-time tracking of breast tumors for navigation during intraoperative radiotherapy. We have validated our methodology on a test cohort of nine patients who underwent tumor resection surgery and intraoperative radiotherapy, and we have quantitatively compared simulation results to intraoperative scans. The accuracy of our simulation results suggest clinical viability of the proposed methodology.

A calibration-free workflow for image-based mixed reality navigation of total shoulder arthroplasty

ABSTRACT Accurate pin placement to guide renaming of the glenoid surface in total shoulder arthroplasty (TSA) is a critical step to restore range of motion in the glenohumeral joint. Achieving proper pin position with free-hand is complicated due to inadequate intra-operative availability of pre-operative planning data. Mixed reality provides a new modality of surgical navigation for arthroplasty without distracting surgeon from the patient anatomy. However, achieving accurate alignment between the pre-operative plan and the intra-operative anatomy is challenging, especially if workflow-compliant solutions are desired. In this paper, we present a calibration-free mixed reality navigation workflow for glenoid pin placement in TSA that contributes to solving some open challenges. We use a visible light stereo camera on a surgical support arm combined with a transformer-based disparity estimation algorithm to accurately reconstruct the 3D anatomy despite surgical lighting. Besides, we introduce a slide-on marker calibrated by design to overcome perceptual difficulties that arise when trying to align real to virtual objects. In a user study on a semi-anthropomorphic phantom, we assess the end-to-end pin placement accuracy using both our system and a clinical reference standard solution that relies on patient-specific drill guides. Averaging over 15 drilled trajectories, our mixed reality system achieved a pin placement accuracy of ( mm, ).

AUGMENTED REALITY NAVIGATION FRAMEWORK FOR TOTAL HIP ARTHROPLASTY SURGERY

In a total hip arthroplasty surgery, correctly implanting the artificial acetabulum and the femoral head is essential for a successful treatment. An augmented reality (AR) navigation framework is proposed in this paper to provide accurate surgical guidance in a total hip arthroplasty procedure. The AR framework consists of three parts: (1) preoperative surgical planning to generate virtual information for AR; (2) computer vision-based tracking for the real-time localization of both acetabular cup positioner and bony landmarks during surgery; (3) registration of a virtual object onto a real-world operative field to properly overlay the preoperative surgical planning data onto a three-dimensional (3D)-printed pelvis model. The cost-effective framework is designed with our clinical partner based on real surgical conditions. The bony landmarks are automatically detected and used for the registration between virtual and real objects. The AR performance is evaluated with a pelvis model, and it presents mean errors of 2.2[Formula: see text]mm and 0.8∘ in position and orientation, respectively, between real and virtual spaces. These small errors are within the tolerance of positive surgical outcomes.

Suitability of Magnetic Resonance Imaging for Guided Endodontics: Proof of Principle

IntroductionThis proof-of-principle study aimed to demonstrate that magnetic resonance imaging (MRI) is sufficiently accurate for the detection of root canals using guided endodontics. MethodsOne hundred extracted human teeth (anterior and premolar) were mounted onto 5 mandibular and 5 maxillary models, fitted with splints designed to accommodate a thin layer of aqueous gel for indirect imaging, and scanned by MRI. After MRI and intraoral scans were aligned using planning software, access cavities were planned virtually, and templates were manufactured with computer-aided design/computer-aided manufacturing, the access cavities were prepared. Cone-beam computed tomographic scans were performed and matched with the virtual preoperative planning data to determine the accuracy of access cavity preparation in terms of deviation between planned and prepared cavities in the mesiodistal and buccolingual dimensions and angle. Descriptive statistical analysis was performed, and the mean values were compared using the t test. ResultsNinety-one of 100 root canals were successfully scouted after MRI-guided access cavity preparation. The mean angle deviation was 1.82°. The mean deviation ranged from 0.21–0.31 mm at the base of the bur and from 0.28–0.44 mm at the tip of the bur. Preparation in the buccolingual dimension was significantly more precise in mandibular compared with maxillary teeth, and accuracy in the mesiodistal dimension was more precise in anterior teeth compared with premolars. ConclusionsThis in vitro study demonstrated the suitability of MRI for guided endodontic access cavity preparation.

An integrated haptic-enabled virtual reality system for orthognathic surgery planning

Conventional Orthognathic surgery (OGS) planning involves cephalometric analyses and dental casts to be mounted on an articulator. Dental segments are subsequently identified, cut and repositioned to allow the fabrication of intraoral wafers that guide the positioning of the osteotomy bone segments. This conventional planning introduces many inaccuracies that affect the post-surgery outcomes. Although computer technologies have advanced computational tools for OGS planning, they have failed in providing a practical solution. Many focuses only on some specific stages of the planning process, and their ability to transfer preoperative planning data to the operating room is limited. This paper proposes a new integrated haptic-enabled virtual reality (VR) system for OGS planning. The system incorporates CAD tools and haptics to facilitate a complete planning process and is able to automatically generate preoperative plans. A clinical pre-diagnosis is also provided automatically by the system based on the patient’s digital data. A functional evaluation based on a real patient case study demonstrates that the proposed virtual OGS planning method is feasible and more effective than the traditional approach at increasing the intuitiveness and reducing errors and planning times.

A retrospective study of the accuracy of template-guided versus freehand implant placement: A nonradiologic method

The aim of this retrospective case study was to evaluate implant placement accuracy in inexperienced clinicians with use of a surgical guide template vs the freehand method for preoperatively planned implant position. Oral implant therapy was performed by inexperienced dental practitioners (<20 implants placed) on eligible patients after cone beam computer tomography (CBCT)-based software planning. Two patients' groups were formed according to the surgical technique: guided and freehand implant placement. The casts used for the fabrication of reconstructions were scanned by using a 3-dimensional (3D) laser scanner, the implant positions were superimposed with preoperative planning data, and the 3D deviations were calculated. Twenty adult patients were included in this retrospective study (20 guided and 21 freehand implant placements). Mean calculated deviations with use of a surgical guide template were significantly lower compared with those of the freehand method with regard to angulation (P = .002), apical position (P = .002), and basal position (P = .012). No significant differences in implant placement accuracy were detected between the groups according to the implant position (premolars/molars; upper jaw/lower jaw) (P > .05). Computer-aided planning and the use of surgical guides in accordance with CBCT images may help inexperienced clinicians to place implants with high accuracy.

Navigated liver surgery : Current state and importance in the future

The preoperative computer-assisted resection planning is the basis for every navigation. Thanks to modern algorithms, the prerequisites have been created to carry out avirtual resection planning and arisk analysis. Thus, individual segment resections can be precisely planned in any conceivable combination. The transfer of planning information and resection suggestions to the operating theater is still problematic. The so-called stereotactic liver navigation supports the exact intraoperative implementation of the planned resection strategy and provides the surgeon with real-time three-dimensional information on resection margins and critical structures during the resection. This is made possible by asurgical navigation system that measures the position of surgical instruments and then presents them together with the preoperative surgical planning data. Although surgical navigation systems have been indispensable in neurosurgery and spinal surgery for many years, these procedures have not yet become established as standard in liver surgery. This is mainly due to the technical challenge of navigating amoving organ. As the liver is constantly moving and deforming during surgery due to respiration and surgical manipulation, the surgical navigation system must be able to measure these alterations in order to adapt the preoperative navigation data to the current situation. Despite these advances, further developments are required until navigated liver resection enters clinical routine; however, it is already clear that laparoscopic liver surgery and robotic surgery will benefit most from navigation technology.

Development of a Virtual Reality Preoperative Planning System for Postlateral Endoscopic Lumbar Discectomy Surgery and Its Clinical Application

Percutaneous endoscopic lumbar discectomy is an effective way to treat lumbar disc herniation. Traditional preoperative planning based on a 2-dimensional method by magnetic resonance/computed tomography may cause inaccuracy of puncture during surgery. We used virtual reality to stimulate a surgery environment and measured relevant 3-dimensional data. We then explored its applicability for increasing puncture accuracy during actual surgeries. A prospective randomized trial of lumbar disc herniation was conducted. Both conventional and virtual reality methods were used for preoperative planning and relevant data (planned puncture point and entry angle) were measured. Data were used during surgery and adjusted to complete the operation. The final entry point and entry angle were recorded and compared with relevant planned data statistically. Fluoroscopic times and location time also were included to access the puncture accuracy during surgery. Thirty cases were included in our study. Both groups achieved good results after surgery, except for 1 case of postoperative dysesthesia in the traditional planning group and 1 case of residual disc in the virtual reality group. The use of virtual reality can predict a surgery-related angle and distance accurately except for depth. Compared with the traditional planning group, the fluoroscopic time (13.18 ± 4.191 vs. 32.00 ± 4.52) and location time (17.91 ± 4.74 vs. 33.22 ± 3.90) were statistically different, which indicates that this method can increase puncture accuracy. A virtual reality planning system is an accurate preoperative planning method that can significantly improve the puncture accuracy of percutaneous endoscopic lumbar discectomy and reduce fluoroscopic and location times.

Robot-guided stereoelectroencephalography without a computed tomography scan for referencing: Analysis of accuracy.

Recent studies with robot-guided stereotaxy use computed tomography (CT) scans for referencing. We will provide evidence that using preoperative MRI datasets referenced with a laser scan of the patient's face is sufficient for sEEG implantation. In total, 40 sEEG electrodes were implanted in five patients by the robotic surgical assistant (ROSA). The postoperative CT scan for identifying electrode positions was fused with the preoperative MRI-based planning data. The accuracy was determined by the target point error (TPE) and the entry point error (EPE), applying the Euclidean distance. The mean TPE amounted to 2.96mm, the mean EPE to 2.53mm. The accuracy was improved in 1.5T MRI: the mean TPE amounted to 1.72mm, the EPE to 0.97mm. No complications, haemorrhages, infections, etc., were observed. Robot-guided sEEG based on 3T MRI reduces radiation exposure for the patient and can still be performed safely.

Projective biomechanical depth matching for soft tissue registration in laparoscopic surgery.

A key component of computer- assisted surgery systems is the accurate and robust registration of preoperative planning data with intraoperative sensor data. In laparoscopic surgery, this image-based registration remains challenging due to soft tissue deformations. This paper presents a novel approach for biomechanical soft tissue registration of preoperative CT data with stereo endoscopic image data. The proposed method consists of two registrations steps. First, we use a 3D surface mosaic from partial surfaces reconstructed from stereo endoscopic images to initially align the biomechanical model with the intraoperative position and shape of the organ. After this initialization, the biomechanical model is projected onto newly captured surfaces, resulting in displacement boundary conditions, which in turn are used to update the biomechanical model. The method is evaluated in silico, using a human liver model, and in vivo, using porcine data. The quantitative in silico data shows a stable behaviour of the biomechanical model and root-mean-square deviation of volume vertices of under 3mm with adjusted biomechanical parameters. This work contributes a fully automatic featureless non-rigid registration approach. The results of the in silico and in vivo experiments suggest that our method is able to handle dynamic deformations during surgery. Additional experiments, especially regarding human tissue behaviour, are an important next step towards clinical applications.

Shape-aware surface reconstruction from sparse 3D point-clouds.

The reconstruction of an object's shape or surface from a set of 3D points plays an important role in medical image analysis, e.g. in anatomy reconstruction from tomographic measurements or in the process of aligning intra-operative navigation and preoperative planning data. In such scenarios, one usually has to deal with sparse data, which significantly aggravates the problem of reconstruction. However, medical applications often provide contextual information about the 3D point data that allow to incorporate prior knowledge about the shape that is to be reconstructed. To this end, we propose the use of a statistical shape model (SSM) as a prior for surface reconstruction. The SSM is represented by a point distribution model (PDM), which is associated with a surface mesh. Using the shape distribution that is modelled by the PDM, we formulate the problem of surface reconstruction from a probabilistic perspective based on a Gaussian Mixture Model (GMM). In order to do so, the given points are interpreted as samples of the GMM. By using mixture components with anisotropic covariances that are "oriented" according to the surface normals at the PDM points, a surface-based fitting is accomplished. Estimating the parameters of the GMM in a maximum a posteriori manner yields the reconstruction of the surface from the given data points. We compare our method to the extensively used Iterative Closest Points method on several different anatomical datasets/SSMs (brain, femur, tibia, hip, liver) and demonstrate superior accuracy and robustness on sparse data.

Surgical treatment of eloquent brain area tumors using neurophysiological mapping of the speech and motor areas and conduction tracts

To evaluate the efficacy of intraoperative neurophysiological mapping in removing eloquent brain area tumors (EBATs). Sixty five EBAT patients underwent surgical treatment using intraoperative neurophysiological mapping at the Pirogov National Medical and Surgical Center in the period from 2014 to 2015. On primary neurological examination, 46 (71%) patients were detected with motor deficits of varying severity. Speech disorders were diagnosed in 17 (26%) patients. Sixteen patients with concomitant or isolated lesions of the speech centers underwent awake surgery using the asleep-awake-asleep protocol. Standard neurophysiological monitoring included transcranial stimulation as well as motor and, if necessary, speech mapping. The motor and speech areas were mapped with allowance for the preoperative planning data (obtained with a navigation station) synchronized with functional MRI. In this case, a broader representation of the motor and speech centers was revealed in 12 (19%) patients. During speech mapping, no speech disorders were detected in 7 patients; in 9 patients, stimulation of the cerebral cortex in the intended surgical area induced motor (3 patients), sensory (4), and amnesic (2) aphasia. In the total group, we identified 11 patients in whom the tumor was located near the internal capsule. Upon mapping of the conduction tracts in the internal capsule area, the stimulus strength during tumor resection was gradually decreased from 10 mA to 5 mA. Tumor resection was stopped when responses retained at a stimulus strength of 5 mA, which, when compared to the navigation data, corresponded to a distance of about 5 mm to the internal capsule. Completeness of tumor resection was evaluated (contrast-enhanced MRI) in all patients on the first postoperative day. According to the control MRI data, the tumor was resected totally in 60% of patients, subtotally in 24% of patients, and partially in 16% of patients. In the early postoperative period, the development or aggravation of a motor neurological deficit was detected in 18 patients: worsening of paresis was observed in 11 patients, and worsening of speech disorders occurred in 7 patients. After 4 months, motor and speech disorders regressed in 10 patients. Therefore, a persistent neurological deficit developed after surgery in 8 (12%) patients (motor deficit in 5 cases; speech deficit in 3 cases). Resection of eloquent brain area tumors using intraoperative neurophysiological monitoring enables complete resection of the tumor at a low risk of persistent neurological deficits, which ultimately improves the patient's life prognosis.

Accuracy evaluation of computer-designed surgical guide template in oral implantology.

The purpose of this study was to assess the accuracy of implant placement using surgical guide templates, and to compare the results with implant placement based on computer-aided design (CAD) planning merely. A total of 60 patients with dentition defects were included in our study, who were equally divided into group I and group II. Preoperative cone beam computed tomography (CBCT) was performed and preoperative planning was designed with Simplant software for all 60 patients. A total of 52 implants were placed in group I patients based on the preoperative planning without surgical guide templates. Implant surgical guide templates for group II patients were designed and produced by a rapid prototyping (RP) technique. A total of 57 implants were inserted in group II patients with the assistance of surgical templates. Postoperative CBCT was performed for all 60 patients. Image registration was carried out between postoperative CBCT data and that of preoperative planning data. Deviations of the implant between the actual and planned positions were measured and compared. There was no significant structure damage during the surgery. Osseointegration was achieved in all implants, and both soft and hard tissues around implants were stable. Variation at the implant shoulder in group II was 1.18 ± 0.72 mm, apex 1.43 ± 0.74 mm, angulation 4.21 ± 1.91 mm, and depth 0.54 ± 0.29 mm, whereas the variation in group I was 2.07 ± 0.51 mm (P < 0.01), 2.89 ± 1.02 mm (P < 0.01), 8.84 ± 4.64 mm (P < 0.05), and 0.78 ± 0.33 mm (P > 0.05). The use of surgical guide templates can achieve higher precision and accuracy in implant shoulder, apex, and angulation, which is much more suitable for complicated procedures and conditions such as the flapless method, immediate loading, aesthetic restoration, and insufficient bone height.

Physics-based shape matching for intraoperative image guidance.

Soft-tissue deformations can severely degrade the validity of preoperative planning data during computer assisted interventions. Intraoperative imaging such as stereo endoscopic, time-of-flight or, laser range scanner data can be used to compensate these movements. In this context, the intraoperative surface has to be matched to the preoperative model. The shape matching is especially challenging in the intraoperative setting due to noisy sensor data, only partially visible surfaces, ambiguous shape descriptors, and real-time requirements. A novel physics-based shape matching (PBSM) approach to register intraoperatively acquired surface meshes to preoperative planning data is proposed. The key idea of the method is to describe the nonrigid registration process as an electrostatic-elastic problem, where an elastic body (preoperative model) that is electrically charged slides into an oppositely charged rigid shape (intraoperative surface). It is shown that the corresponding energy functional can be efficiently solved using the finite element (FE) method. It is also demonstrated how PBSM can be combined with rigid registration schemes for robust nonrigid registration of arbitrarily aligned surfaces. Furthermore, it is shown how the approach can be combined with landmark based methods and outline its application to image guidance in laparoscopic interventions. A profound analysis of the PBSM scheme based on in silico and phantom data is presented. Simulation studies on several liver models show that the approach is robust to the initial rigid registration and to parameter variations. The studies also reveal that the method achieves submillimeter registration accuracy (mean error between 0.32 and 0.46 mm). An unoptimized, single core implementation of the approach achieves near real-time performance (2 TPS, 7-19 s total registration time). It outperforms established methods in terms of speed and accuracy. Furthermore, it is shown that the method is able to accurately match partial surfaces. Finally, a phantom experiment demonstrates how the method can be combined with stereo endoscopic imaging to provide nonrigid registration during laparoscopic interventions. The PBSM approach for surface matching is fast, robust, and accurate. As the technique is based on a preoperative volumetric FE model, it naturally recovers the position of volumetric structures (e.g., tumors and vessels). It cannot only be used to recover soft-tissue deformations from intraoperative surface models but can also be combined with landmark data from volumetric imaging. In addition to applications in laparoscopic surgery, the method might prove useful in other areas that require soft-tissue registration from sparse intraoperative sensor data (e.g., radiation therapy).

P17.75 * UTILITY OF 3D SURGICAL PLANNING FOR RESECTION OF HIGH-GRADE GLIOMAS

OBJECTIVES: Surgical resection of gliomas involving eloquent brain areas carries a high risk of postoperative neurological deterioration. METHODS: Total of 129 patients (75 males, 54 females, mean age 45.5 years, range 20-70 years) underwent preoperative MRI with Gd-enhancement (3D-T1W, T2W, FLAIR, DTI-FT, fMRI). Brain tumors located in eloquent areas (Sawaya grade III) in 93 (72.1%) patients and close to eloquent areas (Sawaya grade II) in 36 (27.9%) patients. The surgical planning and tumor microsurgery resection were carried out using StealthStation navigation system (Medtronic Inc., USA). The surgical planning was performed with a 3D volumetric reconstruction of cerebral hemispheres' surface, tumor, corticospinal tracts, motor areas, ventricles, cerebral arteries, dural sinuses and cortical surface veins. The surgical trajectory and volume of safe tumor resection were defined and calculated preoperative. RESULTS: A gross total tumor resection was achieved in 54 (41.9%) patients, subtotal resection in 61 (47.3%), partial resection in 14 (10.8%). Glioblastomas (WHO Grade IV) were found in 61 (47.3%) cases, anaplastic gliomas (WHO Grade III) _ in 68 (52.7%). Median KPS score increased from 68.4 to 84.8 after surgery (p < 0.05). The neuronavigation system supports the ability of multimodal data sets integration and preoperative planning with using of 3D models presenting anatomical and functional structures. The 3D modeling reveals anatomical relations of tumor with the surrounding eloquent areas and vessels that creates conditions for determination of the optimal surgical tactics. The use of multimodal neuronavigation provided intraoperative orientation by comparing position of virtual structures from preoperative planning data with the anatomical structures in the operative field. CONCLUSION: The 3D surgical planning allows evaluating the risk of injury of eloquent structures, facilitates the orientation in operative field, and reduces the level of neurological disorders in operated patients.

3D–2D registration for surgical guidance: effect of projection view angles on registration accuracy

An algorithm for intensity-based 3D–2D registration of CT and x-ray projections is evaluated, specifically using single- or dual-projection views to provide 3D localization. The registration framework employs the gradient information similarity metric and covariance matrix adaptation evolution strategy to solve for the patient pose in six degrees of freedom. Registration performance was evaluated in an anthropomorphic phantom and cadaver, using C-arm projection views acquired at angular separation, Δθ, ranging from ∼0°–180° at variable C-arm magnification. Registration accuracy was assessed in terms of 2D projection distance error and 3D target registration error (TRE) and compared to that of an electromagnetic (EM) tracker. The results indicate that angular separation as small as Δθ ∼10°–20° achieved TRE <2 mm with 95% confidence, comparable or superior to that of the EM tracker. The method allows direct registration of preoperative CT and planning data to intraoperative fluoroscopy, providing 3D localization free from conventional limitations associated with external fiducial markers, stereotactic frames, trackers and manual registration.