Virtual Placement Research Articles

Incidence of Implant Buccal Plate Fenestration in the Esthetic Zone: A Cone Beam Computed Tomography Study

The aim of this cone beam computed tomography (CBCT) study was to investigate the incidence of fenestration and associated risk factors with virtual placement of an implant in the maxillary incisor region. Edentulous ridges missing a maxillary central or lateral incisor and amenable for single implant placement were included. Root-form implants (4×12 mm and 3.5×12 mm for the central and lateral incisors, respectively) were placed virtually in the edentulous space following the axis of the ipsilateral crown. Buccolingually, the implants were placed in the ideal prosthetic cingulum position. The angles of the ridge (RA) and implants (IA) in relation to the hard palate and the incidence of fenestration were recorded. A total of 48 CBCT scans were analyzed. The mean RA and IA were 124.32 degrees and 110.91 degrees, respectively. Nine cases resulted in fenestration, equivalent to 18.75% of the total cases. The discrepancy between the RA and IA was statistically significantly larger in the fenestration sites (19.93 degrees) than in the nonfenestration sites (13.05 degrees). The concavity depth of the alveolar ridge was statistically significantly higher in the fenestration sites (4.79 mm) than in the nonfenestration sites (3.40 mm). Within the limitations of this study, it can be concluded that the occurrence of fenestration is common (approximately 20%) if an implant is placed in the cingulum position with the axis following that of its restoration.

C1 lateral mass screw placement via the posterior arch: a technique comparison and anatomic analysis

Background contextInstrumentation of C1 is becoming increasingly common. Starting points initially described for C1 lateral mass screws at the lateral mass/posterior arch junction are technically challenging. Recently, a number of techniques have evolved advocating varying starting points and trajectories. Despite being technically easier, there are new safety concerns. Insufficient evidence exists for optimal C1 lateral mass screw placement with starting points in the posterior arch. PurposeTo determine anatomic variability of the C1 lateral mass and posterior ring and to compare safety and feasibility of C1 lateral mass screw placement techniques via the posterior arch. Study designDescriptive anatomy for surgical technique. MethodsOne hundred thin-cut cervical spine computed tomography scans were acquired and formatted for virtual surgery. Four different described techniques were used for virtual placement of C1 lateral mass screws. Success was defined as avoidance of critical structures including the transverse foramen, vertebral groove, and spinal dura. Anatomic variability of the C1 vertebra and safe zones for screw placement were also clarified. ResultsOverall screw placement success for the four techniques was 50% (Resnick), 92% (Tan et al.), 58% (Ma et al.), and 85% (Christensen et al.). Average posterior arch height was 6.7±2.1 mm, and vertebral groove height 4.9±1.1 mm was the most limiting dimension to safe screw placement. A safe zone for screw placement was found in 100% of cases (200 screws), 17.0±1.1 mm from midline and a width of 12.6±1.7 mm. Posterior tubercle morphology was variable. ConclusionsC1 lateral mass screws could be virtually placed bilaterally in each of 100 clinical cases without violating critical structures. However, none of the previously described approaches worked in every case because of significant anatomic variability. The vertical starting point was particularly critical, and vertebral groove height was the most limiting variable. Although a reliable safe zone could be found in every case, preoperative planning is essential to avoid critical structures.

Postoperative assessment of dental implants by using multi-slice computed tomography

Implantology is a fast growing area in dentistry. One of the most common issues encountered in dental implantation procedures is the lack of adequate preoperative planning. Conventional radiography may not be able to assess the true regional three-dimensional anatomical presentation. Multi Slice Computed Tomography provides data in 3-dimentional format offering information on craniofacial anatomy for diagnosis; this technology enables the virtual placement of implant in a 3-Dimensional model of the patient jaw (dental planning). Patients, Material and Methods: The sample consisted of (72) Iraqi patients indicated for dental implant (34 male and 38 female), age range between (20-70) years old. They were examined during a time period started from December 2012 to April 2013. All the patients who subjected to implant treatment depending on the pre-operative panoramic radiograph were referred Al-Kharkh General hospital, spiral CT scan Department, for postsurgical assessment evaluate the angulation of fixture in relation to the angulation of bone in coronal and sagittal sections by using Multi-Detector Computed Tomography. Results: The present study showed that the angulation of implant affected by age, sector, and tooth position in the same jaw, and not affected by gender. Conclusion: Multi-Slice Computed Tomography provides a great understanding about bone angulation, it necessary as a diagnostic tool for treatment planning pre and post-operatively.

Accuracy assessment of cone beam computed tomography‐derived laboratory‐based surgical templates on partially edentulous patients

The aim of the present prospective clinical study was to evaluate the match between the positions and axes of the virtually planned and the placed implants using laboratory-based surgical guides generated from cone beam computed tomography (CBCT). A total of 132 implants were placed with the aid of 3D-based transfer templates in 52 consecutive partially edentulous patients between April 2008 and March 2010. After individual adaptation of the scan templates and CBCT scanning, the acquired data for virtual implant planning and simulation were processed using the med3D software program. After finalizing the virtual placement of the implants the radiographic templates were converted into operative guides containing titanium sleeves for cavity preparation. Preoperative planning was merged with postoperative CBCT data to identify linear and angular deviations between virtually planned and placed implants. Compared with the planned implants the installed implants showed linear deviations in the median at the neck and apex of 0.27 mm (range 0.01-0.97 mm), and of 0.46 mm (range 0.03-1.38 mm), respectively. The angle deviation was 1.84° in median, with a range of 0.07-6.26°. The extent of deviation depends on the size of the tooth gap and the distribution of the remaining teeth. The results of this study suggested that laboratory-fabricated surgical guides using CBCT data may be reliable in implant placement under prosthodontic considerations in partial edentulism.

Incorporating haptic effects into three-dimensional virtual environments to train the hemiparetic upper extremity.

Current neuroscience has identified several constructs to increase the effectiveness of upper extremity rehabilitation. One is the use of progressive, skill acquisition-oriented training. Another approach emphasizes the use of bilateral activities. Building on these principles, this paper describes the design and feasibility testing of a robotic/virtual environment system designed to train the arm of persons who have had strokes. The system provides a variety of assistance modes, scalable workspaces and hand-robot interfaces allowing persons with strokes to train multiple joints in three dimensions. The simulations utilize assistance algorithms that adjust task difficulty both online and offline in relation to subject performance. Several distinctive haptic effects have been incorporated into the simulations. An adaptive master-slave relationship between the unimpaired and impaired arm encourages active movement of the subject's hemiparetic arm during a bimanual task. Adaptive anti-gravity support and damping stabilize the arm during virtual reaching and placement tasks. An adaptive virtual spring provides assistance to complete the movement if the subject is unable to complete the task in time. Finally, haptically rendered virtual objects help to shape the movement trajectory during a virtual placement task. A proof of concept study demonstrated this system to be safe, feasible and worthy of further study.

SU-FF-T-549: Virtual Simulation of Frame Placement for Gamma Knife® PerfexionTM

PURPOSE: To optimize the frame placement for patients receiving stereotactic radio surgery (SRS) using GammaKnife® Perfexion™, a simulation program was developed and its accuracy of collision clearance was compared with the planning system, Leksel Gamma Plan 8.0 (LGP). METHODS AND MATERIALS: A simulation program was designed in Matlab to do the following: import patient DICOM images with or without frame, automatically measure skull dimension from the images, simulate the frame, post, and pin placement, create isocenters, and check for collision for each isocenter. The program employs a graphical user interface that can be compiled to run on a personal computer. MR images from ten study patients were imported into the simulation program. Frame placement at the time of treatment was reproduced using the MR fiducial marker of the image in the simulation program. Post and pin length measured at the time of frame setup were used in the simulation. A total of 600 isocenters were selected for the comparison of clearance computed from the simulation program and from LGP. RESULTS: Average clearance at 600 isocenters tested was 6.7mm (standard deviation (SD) of 2.6 mm) from LGP and 6.9 mm (SD of 2.5 mm) from the simulation program. Mean differences between the computed clearance from the simulation program and LGP were −0.6, −0.3, 0.9 and 0.9 mm in anterior left (AL), anterior right (AR), posterior left (PL) and posterior right (PR) respectively. Standard deviations of the differences were 0.9, 1.0, 1.9, and 1.9 mm in the AL, AR, PL and PR directions respectively. CONCLUSION: A simulation program for virtual frame placement was developed to guide an optimal frame setup for patients receiving SRS using gamma knife Perfexion™. It is a reliable tool that can guide optimal frame setup to reduce the chance of collision.

Real-Time Human Pose Estimation: A Case Study in Algorithm Design for Smart Camera Networks

Monitoring human activities finds novel applications in smart environment settings. Examples include immersive multimedia and virtual reality, smart buildings and occupancy-based services, assisted living and patient monitoring, and interactive classrooms and teleconferencing. A network of cameras can enable detection and interpretation of human events by utilizing multiple views and collaborative processing. Distributed processing of acquired videos at the source camera facilitates operation of scalable vision networks by avoiding transfer of raw images. This allows for efficient collaboration between the cameras under the communication and latency constraints, as well as being motivated by aiming to preserve the privacy of the network users (no image transfer out of the camera) while offering services in applications such as assisted living or virtual placement. In this paper, collaborative processing and data fusion techniques in a multicamera setting are examined in the context of human pose estimation. Multiple mechanisms for information fusion across the space (multiple views), time, and different feature levels are introduced to meet system constraints and are described through examples.

The Virtual Placement: An Alternative to the Traditional Work Placement in the Geographical Sciences?

Work placements are a well-established part of the curricula of many geographical sciences, as are opportunities for online learning. Whilst many aspects of the learning experience for undergraduates have been given an online makeover the placement has remained a ‘real’ experience. This paper considers the potential value of an online placement and outlines pedagogical and technical aspects of the e-MapScholar Virtual Placement. Findings from evaluation of the first Virtual Placement case study are presented and issues regarding wider adoption are raised.

Advanced Surgical Guidance Technology: A Review

To maximize the outcome of implant placement, the use of advanced radiographic procedures such as computerized tomography, along with fabrication of surgical guides, has been advocated to inform surgeons of ideal implant location. More recently, simulation computer software has been introduced to view radiographic images and test potential implant locations. Yet, surgical guides are processed based on ideal tooth position, with little consideration for underlying anatomical limitations, which creates a disconnection between diagnostic planning and surgical restrictions. In response to this "missing link," computer-assisted design and computer-assisted manufacturing, as well as real-time surgical navigation were recently developed to obtain fully integrated surgical and prosthetic planning. Today, there are several technologies available, but, to our knowledge, a systematic assessment of surgical guidance has not yet been performed. Therefore, the aims of this review are to introduce advanced radiographic and software modalities, and present a detailed assessment of computer-assisted design and computer-assisted manufacturing methods and surgical navigation.

Virtual placement of frontal ventricular catheters using frameless neuronavigation: an "unbloody training" for young neurosurgeons.

To evaluate virtually the reliability of freehand puncture of the anterior horn of the lateral ventricle and to provide realistic, but unbloody training for young neurosurgeons. Virtual placement of ventricular catheters was performed repeatedly by neurosurgical doctors and thereafter controlled by neuronavigation. With the help of a frameless stereotactic navigation device they virtually had to hit the anterior horn of the lateral ventricle on the MRI of 29 brains with normal ventricular sizes and 60 pathological ventricles, respectively. The catheter placement was simulated using the pointer of the navigation system (EasyGuide Neuro). The monitor screen was blinded, so that on-line control was impossible. Virtual elongation of the pointer tip was performed on the workstation and the position of the virtual catheter was evaluated on a printout. Virtual freehand catheter placement was performed 145 times into the MRIs of the normal brains. In 66 cases (45%) the site of the catheter tip was judged as accurate as shown by the navigation system. No difference concerning the number of correctly placed catheters was observed when comparing more and less experienced doctors. The results in the 60 pathological MRIs of patients differed with respect to the size of the ventricles: in narrow ventricles an accurate placement succeeded in 7 of 22 cases (32%), moderately enlarged ventricles were accurately hit in 15 out of 32 cases (46%) and wide ventricles in 5 of 6 attempts (83%), respectively. This setup is a simple, practicable tool for neurosurgical education. The virtual freehand placement of ventricular drains controlled by neuronavigation provides an unbloody training of a routine neurosurgical procedure in a realistic setting without the risk of injuring a patient. Neuronavigation systems can serve therefore as a link between learning from observation and handling the real situation.