Planar body-mounted sensors for electromagnetic tracking

Electromagnetic tracking is a safe, reliable, and cost-effective method to track medical instruments in image-guided surgical navigation. However, patient motion and magnetic field distortions heavily impact the accuracy of tracked position and orientation. The use of redundant magnetic sensors can help to map and mitigate for patient movements and magnetic field distortions within the tracking region. We propose a planar inductive sensor design, printed on PCB and embedded into medical patches. The main advantage is the high repeatability and the cost benefit of using mass PCB manufacturing processes. The article presents new operative formulas for electromagnetic tracking of planar coils on the centimetre scale. The full magnetic analytical model is based on the mutual inductance between coils which can be approximated as being composed by straight conductive filaments. The full model is used to perform accurate system simulations and to assess the accuracy of faster simplified magnetic models, which are necessary to achieve real-time tracking in medical applications

Electropermanent magnetic anchoring for surgery and endoscopy

The use of magnets for anchoring of instrumentation in minimally invasive surgery and endoscopy has become of increased interest in recent years. Permanent magnets have significant advantages over electromagnets for these applications; larger anchoring and retraction force for comparable size and volume without the need for any external power supply. However, permanent magnets represent a potential hazard in the operating field where inadvertent attraction to surgical instrumentation is often undesirable. The current work proposes an interesting hybrid approach which marries the high forces of permanent magnets with the control of electromagnetic technology including the ability to turn the magnet OFF when necessary. This is achieved through the use of an electropermanent magnet, which is designed for surgical retraction across the abdominal and gastric walls. Our electropermanent magnet, which is hand-held and does not require continuous power, is designed with a center lumen which may be used for trocar or needle insertion. The device in this application has been demonstrated successfully in the porcine model where coupling between an intraluminal ring magnet and our electropermanent magnet facilitated guided insertion of an 18 Fr Tuohy needle for guidewire placement. Subsequent investigations have demonstrated the ability to control the coupling distance of the system alleviating shortcomings with current methods of magnetic coupling due to variation in transabdominal wall thicknesses. With further refinement, the magnet may find application in the anchoring of endoscopic and surgical instrumentation for minimally invasive interventions in the gastrointestinal tract

Inductive sensor design for electromagnetic tracking in image guided interventions

As the importance and prevalence of electromagnetic tracking in medical and industrial applications increases, the need for customized sensor design has escalated. This work focuses on AC-based electromagnetic tracking systems where off-the-shelf inductive sensors may not be optimal for many medical instruments or tracking applications. We present a repeatable approach for the design, optimisation and implementation of air-core and ferrite-core inductive sensors suitable for AC-based electromagnetic tracking. Coil-based sensors were designed and tested to investigate the effect of the usual coil parameters such as turn count, geometry and core material on sensor tracking accuracy and precision. Our methodologies were experimentally validated using the Anser EMT system which enabled rapid experimental deployment. Experimental performance is reported compared to off-the-shelf sensors. Static tracking errors of less than 2mm were achieved and close correlation with theoretical design sensitivity and precision was observed. This work may represent a valuable tool in the design of bespoke sensors for electromagnetic tracking where customize sensitivity and form factor are critical

ePlant and the 3D Data Display Initiative: Integrative Systems Biology on the World Wide Web

Visualization tools for biological data are often limited in their ability to interactively integrate data at multiple scales. These computational tools are also typically limited by two-dimensional displays and programmatic implementations that require separate configurations for each of the user's computing devices and recompilation for functional expansion. Towards overcoming these limitations we have developed “ePlant” (http://bar.utoronto.ca/eplant) – a suite of open-source world wide web-based tools for the visualization of large-scale data sets from the model organism Arabidopsis thaliana. These tools display data spanning multiple biological scales on interactive three-dimensional models. Currently, ePlant consists of the following modules: a sequence conservation explorer that includes homology relationships and single nucleotide polymorphism data, a protein structure model explorer, a molecular interaction network explorer, a gene product subcellular localization explorer, and a gene expression pattern explorer. The ePlant's protein structure explorer module represents experimentally determined and theoretical structures covering >70% of the Arabidopsis proteome. The ePlant framework is accessed entirely through a web browser, and is therefore platform-independent. It can be applied to any model organism. To facilitate the development of three-dimensional displays of biological data on the world wide web we have established the “3D Data Display Initiative” (http://3ddi.org)

Electromagnetic tracking in guided medical interventions

Electromagnetic tracking is a navigation technology used in guided medical interventions. The technology is gaining popularity in the fields of robotic surgery, catheter navigation and human-machine interface design. Small magnetic sensors provide enable the position and orientation of a surgical instrument to be tracked in real-time without line of sight. This paper discusses how low frequency electromagnetic fields are used as a tracking medium to precisely estimate the pose of magnetic sensors. The quasi-static approach to magnetic field modelling is presented along with number of pose estimation methods. Advantages and disadvantages of each system type are also discussed

Magnetic tracking using a modular C++ environment for image-guided interventions

Magnetic tracking enables instrument tracking for image-guided interventions when no line of sight is available. This paper describes the first steps towards a more cost-effective, modular, and adaptable approach that builds upon prior work in open hardware architectures for magnetic tracking in image-guided interventions. An exemplary C++ framework is implemented and demonstrated with the open-hardware Anser EMT system. System performance in speed, accuracy, and precision of the C++ implementation is analysed. Static positioning accuracy and precision are calculated within the Region of Interest (ROI) and an average position error of 1.0 (Formula presented.) 0.1 mm is demonstrated. Results show an indicative increase in the update rate using the C++ framework and substantially lower memory requirements, compared to the previously optimised Python and Matlab solvers. These preliminary results provide the basis for future development which will integrate the C++ framework in a 3D Slicer module, greatly extending the adaptability of the platform for customisation in advanced image-guided procedures

Cardiovascular Disease, Mortality Risk, and Healthcare Costs by Lipoprotein(a) Levels According to Low-density Lipoprotein Cholesterol Levels in Older High-risk Adults

BackgroundThe value of lipoprotein(a) (Lp[a]) for predicting cardiovascular disease (CVD) across low-density lipoprotein cholesterol (LDL-C) is uncertain.HypothesisIn older high-risk adults, higher LDL and Lp(a) combined would be associated with higher CVD risk and more healthcare costs.MethodsWe included 3251 high-risk subjects (prior CVD, diabetes, or 10-year Framingham CVD risk >20%) age ≥65 years from the Cardiovascular Health Study and examined the relation of Lp(a) tertiles with incident CVD, coronary heart disease (CHD), and all-cause mortality within LDL-C strata (spanning <70 mg/dL to ≥160 mg/dL). We also examined 1-year all-cause and CVD healthcare costs from Medicare claims.ResultsOver a 22.5-year follow-up, higher Lp(a) levels predicted CVD and total mortality (both standardized hazard ratio [HR]: 1.06, P < 0.01), whereas higher LDL-C levels predicted higher CHD (standardized HR: 1.09, P < 0.01) but lower total mortality (standardized HR: 0.94, P < 0.001). Adjusted HRs in the highest (vs lowest) tertile of Lp(a) level were 1.95 (P = 0.06) for CVD events and 2.68 (P = 0.03) for CHD events when LDL-C was <70 mg/dL. One-year all-cause healthcare costs were increased for Lp(a) ($771 per SD of 56 µg/mL [P = 0.03],$1976 for Lp(a) 25-64 µg/mL vs <25 µg/mL [P = 0.02], and $1648 for Lp(a) ≥65 µg/mL vs <25 µg/mL [P = 0.054]) but not LDL-C.ConclusionsIn older high-risk adults, increased Lp(a) levels were associated with higher CVD risk, especially in those with LDL-C <70 mg/dL, and with higher healthcare costs