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Passive Marker Sphere

Choose from two passive marker spheres, each with a special retro-reflective surface that consists of tens of thousands of microbeads to reflect IR light during tracking.

Detect OEM Surgical Instrument Positions with Pinpoint Accuracy

Passive marker spheres are a key component of the Polaris optical measurement solution: when attached to OEM surgical instruments, these navigation markers act as triangulation points for the instrument within the OR space. This is due to the passive marker sphere’s unique retro-reflective surface, which allows the Polaris optical tracker to ‘see’ it during tracking. The passive marker sphere and Polaris optical tracker are used together as an end-to-end solution to localize, detect and track the OEM surgical instruments with pinpoint accuracy. NDI offers two passive marker spheres: the NDI Passive Sphere™ and Disposable Reflective Marker Sphere*.


Radix™ Lens
How are retro-reflective lenses different than passive marker spheres? Keep reading.

High Visibility and Trackability

Although small (with a diameter that measures < 13.5 mm), passive marker spheres are highly visible—and trackable—throughout the entire measurement volume. The tracking range of the passive marker sphere will depend on the defined viewing angle from the Polaris optical tracker and the passive marker sphere’s location within the characterized measurement volume. For example†, using the default maximum viewing angle of ±90° and distance of 2.4 m out from the Polaris optical tracker, the passive marker sphere has an actual range of use of 168.1°.

Optimal Measurement Performance

Passive marker spheres are also used to calibrate the Polaris optical tracker during factory calibration, and during patient registration of the OEM surgical navigation system. It is engineered to maximize optical measurement performance and provide ease of use within the OR.

    • Coated in a special retro-reflective surface that consists of tens of thousands of microbeads that act like precision lenses to reflect IR light.
    • Delivers reliable tracking across different surgical navigation procedures thanks to consistent sphere shape, surface, and placement.
    • Mounts to OEM surgical instruments via a snap-fit sphere post (NDI Passive Sphere) or threaded sphere post (Disposable Reflective Marker Sphere).
    • Packaged in procedural trays that contain the exact number of spheres required by the surgical navigation procedure.
    • Situated in deep-seated tray pockets that make it easy to remove spheres without dropping or dumping.
NDI Passive Sphere™​

NDI Passive Sphere™

Discover more about this 11.5 mm sphere that mounts to OEM instruments via a snap-fit post.

Disposable Reflective Marker Sphere

Learn about this 13 mm sphere that attaches to OEM instruments via a threaded post.

Disposable Reflective Marker Sphere

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Legal Disclaimer
NDI tracking and measurement products are general metrology components that can be integrated into customer products, research experiments, and/or as components of medical devices that require precision measurement and tracking. While NDI components and technology can be integrated into original equipment manufacturer (OEM) medical devices, they are not specifically intended for a given application and, as such, have not been developed or manufactured in accordance with medical device standards. It remains the responsibility of the OEM customer or end-user to determine and test the suitability of NDI components and technology for their intended use, including performing any required ethics approval, verification, and validation required to demonstrate suitability and compliance. System-level testing, certification, and validation are the responsibility of the original equipment manufacturer or the applicable end-user and should be completed prior to the use of NDI products or technologies in any application.

*The NDI Passive Sphere and Disposable Reflective Marker Sphere are FDA-regulated medical devices. 
Example is based on the NDI Passive Sphere, which measures 11.5 mm in diameter.