Navigation Protocol Research Articles

Non-assisted versus neuro-navigated and XperCT-guided external ventricular catheter placement: a comparative cadaver study

Accurate placement of an external ventricular drain (EVD) for the treatment of hydrocephalus is of paramount importance for its functionality and in order to minimize morbidity and complications. The aim of this study was to compare two different drain insertion assistance tools with the traditional free-hand anatomical landmark method, and to measure efficacy, safety and precision. Ten cadaver heads were prepared by opening large bone windows centered on Kocher's points on both sides. Nineteen physicians, divided in two groups (trainees and board certified neurosurgeons) performed EVD insertions. The target for the ventricular drain tip was the ipsilateral foramen of Monro. Each participant inserted the external ventricular catheter in three different ways: 1) free-hand by anatomical landmarks, 2) neuronavigation-assisted (NN), and 3) XperCT-guided (XCT). The number of ventricular hits and dangerous trajectories; time to proceed; radiation exposure of patients and physicians; distance of the catheter tip to target and size of deviations projected in the orthogonal plans were measured and compared. Insertion using XCT increased the probability of ventricular puncture from 69.2 to 90.2 % (p = 0.02). Non-assisted placements were significantly less precise (catheter tip to target distance 14.3 ± 7.4 mm versus 9.6 ± 7.2 mm, p = 0.0003). The insertion time to proceed increased from 3.04 ± 2.06 min. to 7.3 ± 3.6 min. (p < 0.001). The X-ray exposure for XCT was 32.23 mSv, but could be reduced to 13.9 mSv if patients were initially imaged in the hybrid-operating suite. No supplementary radiation exposure is needed for NN if patients are imaged according to a navigation protocol initially. This ex vivo study demonstrates a significantly improved accuracy and safety using either NN or XCT-assisted methods. Therefore, efforts should be undertaken to implement these new technologies into daily clinical practice. However, the accuracy versus urgency of an EVD placement has to be balanced, as the image-guided insertion technique will implicate a longer preparation time due to a specific image acquisition and trajectory planning.

Sensor Network Navigation without Locations

We propose a pervasive usage of the sensor network infrastructure as a cyber-physical system for navigating internal users in locations of potential danger. Our proposed application differs from previous work in that they typically treat the sensor network as a media of data acquisition while in our navigation application, in-situ interactions between users and sensors become ubiquitous. In addition, human safety and time factors are critical to the success of our objective. Without any preknowledge of user and sensor locations, the design of an effective and efficient navigation protocol faces nontrivial challenges. We propose to embed a road map system in the sensor network without location information so as to provide users navigating routes with guaranteed safety. We accordingly design efficient road map updating mechanisms to rebuild the road map in the event of changes in dangerous areas. In this navigation system, each user only issues local queries to obtain their navigation route. The system is highly scalable for supporting multiple users simultaneously. We implement a prototype system with 36 TelosB motes to validate the effectiveness of this design. We further conduct comprehensive and large-scale simulations to examine the efficiency and scalability of the proposed approach under various environmental dynamics.

Reducing Energy Consumption in Wireless Sensor Networks Using Hash Distribution Table

Reducing Energy Consumption in Wireless Sensor Networks Using Hash Distribution Table Wireless sensor networks include many small sensor nodes. These nodes have limitations with respect to energy level, bandwidth, processing power, and memory. Because of these limitations, navigation, clustering, reduction of energy consumption, an increase of lifespan are much challenges in navigation through wireless sensor networks. This article presents a dispersed navigation protocol called “Bloom Filter”, which is based on older navigation protocols including Anita Kanavalli. Its aim is to optimize energy consumption of networks. This protocol was simulated using NS_2 and assessed. This study well with inexact and nonhomogeneous input and does not require heavy processing. This scheme uses the number of “sends” to a node instead of that node’s residual energy to determine its eligibility as a receiving node, and these results in drastic energy savings.

Geometric properties of graph layouts optimized for greedy navigation

The graph layouts used for complex network studies have been mainly developed to improve visualization. If we interpret the layouts in metric spaces such as Euclidean ones, however, the embedded spatial information can be a valuable cue for various purposes. In this work, we focus on encoding useful navigational information to geometric coordinates of vertices of spatial graphs, which is a reverse problem of harnessing geometric information for better navigation. In other words, the coordinates of the vertices are a map of the topology, not the other way around. We use a recently developed user-centric navigation protocol to explore spatial layouts of complex networks that are optimal for navigation. These layouts are generated with a simple simulated annealing optimization technique. We compare these layouts to others targeted at better visualization and discuss the spatial statistical properties of the optimized layouts for better navigability and its implication.

Navigability and Reachability Index for Emergency Navigation Systems Using Wireless Sensor Networks

Emergency navigation with a large number of sensors can serve as a safety service in emergencies. Recent studies have focused on navigation protocols to safely guide people to exits while helping them avoid hazardous areas. However, those approaches are not applicable in all circumstances. Both the dynamics of the environment and the mobility of users are key challenges for the efficiency and effectiveness of navigation protocols. The concepts of navigability and reachability are used to evaluate three typical navigation approaches. A large number of simulation results show that these two indicators effectively identify the performance levels of navigation protocols in changing environments.

Traumatic Intracerebral Hemorrhage—To Operate or Not?

To report our clinical experience with an advanced navigation protocol that provides seamless integration into the operating workflow of endoscopic transsphenoidal surgery.From 32 consecutive cases of endoscopic transsphenoidal surgery, an optimal setup of continuous electromagnetic instrument navigation was created. Additionally, our standard multimodality image navigation of T1-weighted magnetic resonance (MR) images for soft tissue, MR angiogram for vascular structures, and computed tomography (CT) for solid bone was advanced by the addition of a CT surface rendering for fine paranasal sinus structures. The anatomic structures visualized and their clinical impacts were compared between standard and advanced visualization protocol. Bone-windowed CT images served as reference. The accuracy of the navigation setup was assessed by intraoperative landmark tests. Potential tissue shift was calculated by comparing pre- and postoperative MR angiograms of 20 macroadenomas.After a learning curve of 2 cases (1 ferromagnetic interference and 1 dislocation of the patient reference tracker), the advanced navigation protocol was feasible in 30 cases. Advanced multimodality imaging was able to visualize significantly finer paranasal sinus structures than multimodality image navigation without CT surface rendering, equal to bone-windowed CT images (P < 0.001, McNemar test). This was found helpful for orientation in cases of complex sphenoid sinus anatomy. The accuracy of the advanced navigation setup corresponded to standard optic navigation with skull fixation. A tissue shift of median 2 mm (range 0–9 mm) was observed in the posterior genu of the internal carotid arteries after tumor resection.The advanced navigation protocol permits continuous suction-tracked navigation guidance during endoscopic transsphenoidal surgery and optimal visualization of solid bone, fine paranasal sinus structures, soft-tissue and vascular structures. This may add to the safety of the procedure especially in cases of anatomical variations and in cases of recurrent adenomas with distorted anatomy.

Fijación vertebral posterior guiada por neuronavegación: Experiencia en 121 casos

The authors present the results of a series of 121 cases of posterior vertebral fixation carried out from Sept 2008 to Sept 2010 using Flouro 2D-TC assisted Vector Vision o Kolibri navigator. ( Brain LAB, Feldkirchen, Germany). The sample included 68 males and 53 females. Age range was 24-75 with an average of 50.35., all with indication for instrumentation by different pathologies. Patients presenting vertebral lesions of varying ethiology and lesion level with vertebral posterior fixation indication were included in the study. All underwent a CT before surgery, according to navigation protocol, and the images obtained were merged in the navigator with those obtained in the operating room with a Flouro 2D, which allowed a high quality 3D reconstruction to be performed and thus the capacity to navigate in a real-virtual manner. To evaluate the results of the implant a post-op CT was performed and the position of the implant was defined according to the Heary scale. The calabration time of the material was also evaluated, number of shots with the Flouro-2D, and for clinical evaluation VAS scales were employed, Oswestry and JOA (L), as well as the degree of satisfaction and acceptance of the procedure. A total of 580 screws were implanted, distributed in 62 cervicals of which 24 were in C1-C2, 38 dorsals, 370 lumbar and 110 sacral. Open surgery was performed in 42 cases, MIS in 28 and percutaneous in 51. The presision of the implant was 98.45% with a global deviation of 1.55%, that according to the Heary scale was distributed in grade ll: 2 (1 cervical, 1 lumbar) grade lll: 4 (1 cervical, 2 dorsal, 1 lumbar), grade IV: 3 (1 cervical, 2 lumbar). General average time of calibration per procedure was 2 min. 49 seconds and the mean flouroscopic exposure was one shot at cervical and dorsal and two shots at lumbar level. The clinical evaluation at one month of 121 patients was 8.6/3.0 in the VAS, 68.0% / 23.0% in Oswestry and 6.4/13.1 in JOA (L), with those parameters remaining stable at 3 months in 100 and at 6 months in 87 patients respectively, and the degree of satisfaction between being completely and very satisfied with the procedure was 94.9%, and those who would submit to another treatment was more than 94%. Navigation with Flouro-2D-CT is a high precision technique that reduces complications of varying severity according to the level operated well as number of reinterventions, radiation exposure and surgical time.

The Contribution of Mobile Bearing Knee Design in Optimizing Tibial Rotation in Total Knee Arthroplasty

Abstract This study assessed the alignment and rotation in mobile bearing total knee arthroplasty (TKA) with the tibia cut first technique using an imageless referencing computer navigation protocol evaluating 41 patients. Prerelease mechanical alignment (MA) averaged 7° varus +/−5° (Range: 8° valgus to 20° varus). Post implant MA was 0.5° varus +/−1.2° (Range: 2° valgus to 3° varus). Post operative radiographic MA was 0.3° varus +/−1.3° (Range: 2° valgus to 2° varus). The baseline measurement of tibial rotation from 0° to 90° flexion was 6°+/−7.2° of tibial internal rotation (Range: 8° external rotation to 19.5° internal rotation). The post implant tibial rotation from 0° to 90° flexion was 3.6°+/−8° of tibial internal rotation (Range: 17° external rotation to 29° internal rotation). Of the baseline group, 25 % demonstrated tibial external rotation with flexion. After TKA, 28 % had tibial external rotation with flexion. When comparing the nominal tibial position in relation to the femur at 0° before and after TKA, the tibial rotation point at 0° moved more externally in 21 % and more internally in the rest with mean change for the overall group of 3.9° of internal rotation (Range: 17° internal to 5° external). This study identified significant changes in knee rotation that may be caused by correction of alignment and deformity. Mobile bearing implants by nature of unconstrained rotation are likely to accommodate these variations. This feature could be defined as a significant advantage over fixed-bearing prostheses.

Map-reading Strategy to Diagnose Root Perforations Near Metallic Intracanal Posts by Using Cone Beam Computed Tomography

Introduction To determine the diagnostic hypothesis on the basis of periapical radiography (PR) is a great challenge for radiologists and endodontists. Visualization of three-dimensional structures, available with cone beam computed tomography (CBCT), favors precise definition of the problem and treatment planning. However, metallic artifact effect of intracanal posts might also induce untrue images. The aim of this article is to suggest a map-reading strategy to diagnose root perforations near metallic intracanal posts (ICPs) by using CBCT. Methods and Results The incapacity to locate correctly the position of root perforation might lead to clinical failures. One strategy to minimize metallic artifact in root perforation associated with ICP is to obtain sequential axial slices of each root, with an image navigation protocol from coronal to apical (or from apical to coronal), with axial slices of 0.2 mm/0.2 mm. This map reading provides valuable information showing dynamic visualization toward the point of communication between the root canals and the periodontal space, associated with radiolucent areas, suggesting root perforation. Conclusions The accurate management of CBCT images might reveal abnormality that is unable to be detected in conventional PR. A map-reading approach reduces problems related to detection of root perforations near metallic artifacts. The final diagnosis should always be made in conjunction with the clinical findings.

CT-Based, Fiducial-Free Frameless Stereotaxy for Difficult Ventriculoperitoneal Shunt Insertion: Experience in 26 Consecutive Patients

Background:Patients with small or dysmorphic ventricles requiring ventriculoperitoneal shunt (VPS) insertion for hydrocephalus can be challenging. The ‘freehand’ technique does not always provide for accurate catheter insertion, particularly in patients with slit ventricles, complex hydrocephalus or displaced ventricles. Consequently, many surgeons use stereotaxy for assistance. We have employed a frameless stereotactic technique, obviating the need for fiducials or preoperative MRI, for difficult ventricular catheter placement over the past 1.5 years with excellent results. We describe our experience with frameless stereotactic VPS insertion. Methods:We retrospectively reviewed the charts of 26 patients who underwent frameless stereotactic VPS insertion. All patients had preoperative CT scans using a navigation protocol and were registered into the Stealth Station via the face tracer program. Catheters were inserted using the Medtronic frameless trajectory guide kit. We recorded demographic data, operative time, complications and follow-up. Results:The mean patient age was 31 years. The average operative time was 46 min. There were 3 complications. The average follow-up was 5 months. Twenty-one patients had postoperative imaging, with 20 having excellent catheter positioning. Conclusions:Our results confirm that frameless stereotactic VPS without fiducial marker placement is a feasible technique for catheter insertion in patients who have small/dysmorphic ventricles. In experienced hands, there is negligible added operative time and a low complication rate.

Multi-factorial analysis of time efficiency in total knee arthroplasty

The objective of this retrospective review was to determine whether time efficiency could be gained by optimizing the navigation protocol based on a surgeon's specific technique and work flow. Three groups of 30 consecutive patients operated on by the same surgeon were studied. The groups were from three distinct periods between 2002 and 2008. The first group consisted of patients in which no navigation was performed (the control group); the second group consisted of patients in which navigation was performed using a standard protocol; and the third group consisted of patients in which navigation was performed using a customized protocol that eliminated certain steps. Statistical analysis considered analysis of variance for covariates of total time in the operating room, duration of the procedure, and tourniquet time. Chi-square analysis considered categorical variables of age, gender, body mass index (BMI), Knee Society score, and patellar resurfacing against the surgical group. Multiple linear regression analysis evaluated surgical time adjusted for preoperative deformity, BMI, and patellar resurfacing. In the adjusted model, the customized navigation protocol significantly reduced the surgical time by 10 minutes compared to the non-customized navigation. Not resurfacing the patella significantly reduced the surgical time by 9 minutes. Variables of age, gender, BMI, preoperative deformity and Knee Society score were not related to differences in operating time. Time efficiency may be gained with the use of improved computer navigation protocols and patellar non-resurfacing. [Level of evidence: Level 3.]

Accuracy and Precision of Measurements of Transect Length and Width Made with a Remotely Operated Vehicle

Remotely operated vehicles (ROVs) have been used to estimate the density of fish and invertebrates on strip transects. However, there is little published information about the accuracy and precision of measurements of transect length and width, a critical component of the density estimate. In this study, we evaluate straight line constant velocity protocols, the accuracy and precision of estimates of transect length from ultra short baseline acoustic tracking, and compare measurements of transect width based on sonar and lasers. When ROV tracking was compared to distances measured on sonar maps, the difference between linear tracked and mapped distance (|LDt-LDm|) averaged 1.7 ± 0.5 m. The error was not significantly different with distance. Our navigation protocols allowed us to maintain relatively constant heading and speed. Distance computed from velocity exceeded mapped distance by 2-4 m. The error was not significantly different with distance. Measurements of transect width made with lasers and sonar were comparable, particularly when the ROV was within 4 m of the substrate. Based on our data, ROV tracking can be used to measure transect length within 2 m. If tracking fails, distance can be estimated from velocity within 2-4 m. Sonar can be used to measure transect width with considerable cost savings.

A multidimensional framework for SME e‐business progression

PurposeThis paper sets out to critique the applicability of e‐commerce staged models in explaining the progression of small and medium‐sized businesses (SMEs) in their use of internet technologies. The premise of this study is that examining the evolution of web sites over time gives us insights into actual evolving strategies and motivations behind internet investments.Design/methodology/approachAn alternative multidimensional framework is proposed that combines three different dimensions of organizational change (process, content, and drivers). The content or categories of the dimensions are defined and justified. A study of 192 web sites and their evolution is described. This helps to demonstrate the relevance and applicability of the dimensions of the framework.FindingsThe study describes the different approaches (monitoring, content analysis and case studies) and the characteristics of changes on these web sites. It was found that the main evolution strategies were “content updates” and “dormant sites”. In addition, the majority of companies seem to have evolved their web sites to refresh the image and change navigation protocols and not to add transactional e‐commerce features.Practical implicationsThe proposed framework is argued to be useful to academics, providing multiple perspectives, enabling more insightful study of SMEs' e‐business adoption and progression, and avoiding over‐simple a priori theory, e.g. staged models. The framework is also argued to be useful for SME managers seeking to make the most of their limited resources in this context.Originality/valueThe paper provides a multidimensional framework which is new and comprehensive. It also provides some research findings using the framework relating to a pilot study of 192 SME web sites. Little prior research has been carried out on the evolution of SMEs' web sites, in terms of the type of drivers, the features that have been incorporated over time, and how they have changed.

Navigation protocols in sensor networks

We develop distributed algorithms for adaptive sensor networks that respond to directing a target through a region of space. We model this problem as an online distributed motion planning problem. Each sensor node senses values in its perception space and has the ability to trigger exceptions events we call “danger” and model as “obstacles”. The danger/obstacle landscape changes over time. We present algorithms for computing distributed maps in perception space and for using these maps to compute adaptive paths for a mobile node that can interact with the sensor network. We give the analysis to the protocol and report on hardware experiments using a physical sensor network consisting of Mote sensors. We also show how to reduce searching space and communication cost using Voronoi diagram.

Web Presence Transformations in the 1990s: An Analysis of Press Releases

Many organizations are constantly changing their web presence. Despite the frequency of these redesigns, there appears to be little evidence to explain what kinds of changes are incorporated into each updated version of a web presence. To understand how commercial organizations transform their web presence, we conduct a content analysis and a cluster analysis of press releases describing redesign initiatives in the late 1990s. Findings suggest that the majority of companies redesigned their web presence to expand information and change navigation protocols. Surprisingly, the addition of interactive features such as online ordering and community communication channels is present in only 20% of the redesign cases studied. According to the groups provided by the cluster analysis, most of the changes reported in these press releases are centered on improving the usability of the web presence. Based on this evidence we conclude that initial transformations to commercial websites were more driven by the need to effectively communicate new information than by the addition of e-commerce features.

Navigated vs. conventional implant insertion for maxillary single tooth replacement

Abstract Introduction: Computer-guided navigation has proven a valuable tool in several surgical disciplines. During oral implant placement, its application is intended to accomplish optimal implant localization and to reduce the risk of damage to adjacent structures. The aim of this study was to compare the precision limits of conventional vs. navigated implant insertion in practice. In cast models of the maxilla, implants were inserted to replace the left central incisor (n = 40) and the right canine (n = 40); each of those were inserted either conventionally (n = 20) or navigated (n = 20). Implant position, angulation and insertion depth were calculated from computer tomography scans of the implants that were connected to an index abutment of 40 cm length. The variations of implant positions were reduced for implants that were inserted by navigation (P < 0.05). In both the axial and the transversal plane, the variations of implant angulations were reduced for implants that were inserted by a navigation protocol (P < 0.05). The variations of insertion depth were less (P < 0.05) when the implants were placed by navigation in comparison with conventional insertion procedures. Given the experimental conditions, although they tried to mimic a clinical situation, no final conclusions can be drawn. The in vitro application of a navigation system resulted in an improved precision of insertion surgery regarding the position, angulation and depth of an implant. Clinical studies will have to prove if routine image guidance will result in superior surgical outcome.

Anatomical landmarks for image registration in frameless stereotactic neuronavigation.

Frameless stereotactic navigation devices require preoperative application of skin markers (SM) and planning radiography, which limits their even wider use. Therefore, we prospectively studied the applicability and accuracy of anatomic "natural" markers (NM) for image registration. The accuracy of NM was evaluated in 26 patients operated on in the supine (n=24) or sitting (n=2) position, either by comparison to our standard navigation protocol using SM and planning radiography or by the deviation of anatomic landmarks using a routine diagnostic radiograph. In 21 cases, NM were compared to SM with planning radiography (computed tomography, or CT, in nine cases and magnetic resonance imaging, or MRI, in 12). The root mean square error (RMSE) of the registered volume was calculated by the Philips EasyGuide Neuro frameless stereotactic navigation system and compared between the two registration modalities. The mean RMSE was 3.2 mm+/-1.0 mm standard deviation using NM vs 2.9+/-1.0 mm using self-adhesive SM (P=0.13, Student's t-test). Computed tomography was slightly more accurate than MRI planning (mean RMSE 3.2 mm vs 3.3 mm). In three cases, diagnostic radiography (MRI) was used with a mean RMSE of 5.3 mm but acceptable intraoperative landmark correlation. Our pilot study demonstrates insignificant loss of registration accuracy using NM compared to SM. Additionally, the radiologic planning investigation and accuracy loss due to SM movement may be avoided.