Distorter Characterisation Using Mutual Inductance in Electromagnetic Tracking

In the context of climate change conditions, addressing the shifting composition of forest stands and changes in traditional forest management practices are necessary. For this purpose, understanding the biomass allocation directly influenced by crown architecture is crucial. In this paper, we want to demonstrate the possibility of 3D mensuration of canopy architecture with the digitizer sensor Fastrak Polhemus and demonstrate its capability for assessing important structural information for forest purposes. Scots pine trees were chosen for this purpose, as it is the most widespread tree species in Europe, which, paradoxically, is very negatively affected by climate change. In our study, we examined young trees since the architecture of young trees influences their growth potential. In order to get the most accurate measurement of tree architecture, we evaluated the use of the Fastrak Polhemus magnetic digitizer to create a 3D model of individual trees and perform a subsequent statistical analysis of the data obtained. It was found that the stand density affects the number of branches in different orders and the heights of the trees in the process of natural regeneration. Regarding the branches, in our case, the highest number of branch orders was found in the clear-cut areas (density = 0.0), whereas the lowest branching was on-site with mature stands (density = 0.8). The results showed that the intensity of branching (assessed as the number of third-order branches) depends on the total number of branches of the tree of different branch orders but also on stand density where the tree is growing. An important finding in this study was the negative correlation between the tree branching and the tree height. The growth in height is lower when the branching expansion is higher. Similar data could be obtained with Lidar sensors. However, the occlusion due to the complexity of the tree crown would impede the information from being complete when using the magnetic digitizer. These results provide vital information for the creation of structural-functional models, which can be used to predict and estimate future tree growth and carbon fixation.

Section: Discussionmentioning

confidence: 99%

Measuring the Canopy Architecture of Young Vegetation Using the Fastrak Polhemus 3D Digitizer

Šleglová,

Brichta,

Bílek

et al. 2023

“…AC electromagnetic tracking systems are typically based on Faraday’s law to induce a voltage in a search coil [ 1 , 17 , 20 , 21 ]. EM tracking generally operates with magnetic fields from multiple sources that are spatially varying functions given by:

where x , y , and z are the Cartesian coordinates of a sensor relative to the magnetic source.…”

Section: Methodsmentioning

confidence: 99%

A Radiolucent Electromagnetic Tracking System for Use with Intraoperative X-ray Imaging

O’Donoghue¹,

Jaeger²,

Cantillon-Murphy

2021

In recent times, the use of electromagnetic tracking for navigation in surgery has quickly become a vital tool in minimally invasive surgery. In many procedures, electromagnetic tracking is used in tandem with X-ray technology to track a variety of tools and instruments. Most commercially available EM tracking systems can cause X-ray artifacts and attenuation due to their construction and the metals that form them. In this work, we provide a novel solution to this problem by creating a new radiolucent electromagnetic navigation system that has minimal impact on -ray imaging systems. This is a continuation of our previous work where we showed the development of the Anser open-source electromagnetic tracking system. Typical electromagnetic tracking systems operate by generating low frequency magnetic fields from coils that are located near the patient. These coils are typically made from copper, steel, and other dense radiopaque materials. In this work, we explore the use of low density aluminum to create these coils and we demonstrate that the effect on X-ray images is significantly reduced as a result of these novel changes in the materials used. The resulting field generator is shown to give at least a 60% reduction in the X-ray attenuation in comparison to our earlier designs. We verify that the system accuracy of approximately 1.5 mm RMS error is maintained with this change in design.

“…For example, a set of sensors placed around the operative region can track and compensate for respiratory or cardiac movements [ 23 ], or they can evaluate the field at multiple locations and perform the real-time compensation of field distortions by dynamically correcting the field model. Another possible application of the methods presented in this article involves the tracking of the planar transmitter coils of one or more field generators [ 24 , 25 ]. In this scenario, the reciprocal position between two boards can be determined by tracking the position of the coils of one board with respect to the other.…”

Section: Introductionmentioning

confidence: 99%

Planar Body-Mounted Sensors for Electromagnetic Tracking

Cavaliere

Jaeger

O’Donoghue³

et al. 2021

Self Cite

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.