An 84-year-old female, an ex-smoker, presenting with a 1.6 cm nodule in the right lower lobe. Navigation to the 7th generation airways was performed using the SPiN Vision™ bronchoscope, with a 4 mm outer diameter (OD) and a 2.0 mm working channel (WC)
The SPiN Thoracic Navigation System™ SYS-4000
SPiN Vision™ Bronchoscope, 4mm OD, 2.0mm WC
adenocarcinoma
Physicians frequently use the term 'GPS' when explaining electromagnetic navigation bronchoscopy to patients. We will begin by explaining what a global positioning system (GPS) is, followed by a detailed discussion of the principles of electromagnetic science. Finally, we will demonstrate how the tracking system operates in this context.
How does GPS work?
GPS, or global positioning system, is a worldwide radio-navigation system consisting of a constellation of satellites orbiting the Earth and their corresponding ground stations. Each satellite broadcasts radio signals containing information about its location and the precise time the signal was sent. A GPS receiver captures these signals and calculates the distance to each satellite. By triangulating signals from at least three satellites (and ideally four), the GPS can determine an exact position on Earth.
The GPS helps identify your current location or the location of your choice. A navigation system, on the other hand, is specialized software that uses GPS signals. After the GPS determines the coordinates, the navigation system consults a map database to calculate and provide routing information. By combining real-time position data with electronic mapping technology, the navigation system generates directions to the desired destination.
In vehicle GPS navigation, the map provides a 2D travel route, guiding the car toward a fixed destination. Movement is along longitude and latitude lines, but altitude and rotational data are not included. Only two degrees of freedom—forward/backward and left/right—are reported, which simplifies the navigation process but omits additional spatial information.
Now that we’ve reviewed how GPS and navigation work, let’s move on to electromagnetic navigation.
If you ask, 'What is electromagnetism?' the answer is that it is one of the four fundamental forces of nature, along with gravity, the weak force, and the strong force. The Earth itself acts as a giant magnet, continuously generating a magnetic field.
To better understand this, imagine using a small compass to map the magnetic field around a bar magnet, as shown below. The compass needle will align itself, pointing away from the north pole and toward the south pole of the magnet. By connecting the points obtained by moving the compass, we can visually outline the magnetic field lines.
A permanent magnet is an object made from a material that is magnetized and creates its own permanent magnetic field. In contrast, an electromagnet is created by wrapping a coil of wire around an iron core and passing an electrical current through it, which generates a magnetic field. The key advantage of an electromagnet is its flexibility: it can be assembled into different configurations and can be switched on and off as needed.
Electromagnetic tracking provides real-time information on the position and orientation of the instruments we use within three-dimensional imaging datasets. This technology allows us to navigate within a patient's body and track the tools in use.
To apply the GPS analogy to procedural navigation applications: the patient’s imaging datasets serve as the 'roadmap,' the target lesion is the 'destination,' and the instrument equipped with a sensor acts as the 'vehicle.' The most crucial element of any navigation system is having an accurate 'roadmap'—no matter how advanced the system or tool being used.
An electromagnetic tracking system generally consists of three main components: the field generator, the sensor, and the central unit.
The field generator contains a series of coils of wire arranged in a specific configuration. It emits low-intensity electromagnetic fields at various frequencies. The electromagnetic sensors, which are embedded into the medical instrument, capture these signals at a set refresh rate. When the sensors detect the electromagnetic fields, they generate electrical signals (or voltage), which are then transmitted to the control unit.
The control unit manages the field generator and collects data from the sensors. It processes this information to calculate the position and orientation of the sensors, and then displays the results on a monitor, providing real-time tracking.
To our knowledge, there is no head-to-head published data comparing different electromagnetic navigation platforms, so no platform has been definitively shown to be superior to others.
Conclusion:
There is ongoing development of various navigational bronchoscopy platforms. It is crucial to understand both the performance and limitations of the navigation system being used. A solid understanding of its fundamental principles is essential for ensuring successful use.
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