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Handheld Optical Measurement for Electrode Localization


The Polaris® Krios handheld digitizing scanner integrates into OEM neurodiagnostic equipment to measure, identify, and map electrode positions (via attached markers) in EEG, MEG, NIRS, PSG, and ECG tests. The Polaris Krios is based on optical 3D measurement technology that scans up to 256 markers in less than 2 minutes to an accuracy within 0.5 mm and repeatability of 0.1 mm. Real-time compensation for data variability ensures only actual markers are measured for mapping and registration purposes.

NDI’s extensive API library provides neurodiagnostic equipment manufacturers with seamless integration and management of this electrode measurement data; for example, recording and naming electrodes against a preset 10-20 electrode placement model. The Krios complements the workflow of existing neurodiagnostic systems by reducing the time and complexity of electrode registration and identification. The electrode setup process, which can be time-consuming and difficult for operators, now takes only minutes.


Benefits of the Polaris® Krios to Neurodiagnostic OEMs and Operators

  • Lightweight Ergonomic Scanner
    Operate the Krios with ease – its balanced one-hand grip, handy start/stop trigger button, color-coded LED status indicator lights, and audio cues maximize scanning efficiency.
  • Integrated Touch Probe
    Improve the detection of obstructed electrodes and electrode positioning with one-touch localization and registration of fiducial points such as the nasion, inion, and preauricular points.
  • No Marker Calculations
    Scan right away – self-calibrating markers attach to any sized or shaped electrode, in any order. No position calculations or sequencing are required. Marker positions are automatically mapped.
  • Accurate and Reliable Data Collection
    Capture marker positions to an accuracy within 0.5mm and repeatability of 0.1mm. Only actual markers are measured for electrode mapping purposes.
  • Automatic Registration Process
    Save significant electrode registration time – up to 256 markers can be scanned in less than 2 minutes. Markers are then automatically mapped and registered within the OEM’s neurofeedback software.


How the Polaris® Krios Works

The Polaris Krios is based on optical measurement technology; the scanner uses light reflected by markers to determine their position coordinates.

place scan probe
  1. Attach each electrode (with a prefixed marker) to the scalp or cap.
  1. Scan the head with the Krios to localize each marker’s position. This localization process creates a digital point cloud (3D model) and a rigid body of marker coordinates.
  1. Probe anatomical features to establish fiducial (reference) points with respect to the rigid body, such as the nasion, inion, and preauricular points of the subject’s head.


The rigid body is transformed from the Krios coordinate system to the subject coordinate system. Using the Krios software, operators can append notes to electrode positions. The final point cloud with all identified marker coordinates, fiducial points, and notes, is saved as a .CSV file for export to the neurofeedback software.  The point cloud can then be mapped to a pre-defined electrode configuration within the neurofeedback software.


Polaris® Krios Technical Specifications

Scanner Specifications
Dimensions (LxWxH) 155 mm x 75 mm x 300 mm
Weight 860 g
Power Requirements 100-250 V AC ~50/60 Hz, 1 A
Sensor Specifications
Measurement Volume 883 mm x 840 mm x 928 mm
Update Frequency 20, 30, 60 Hz
Scan Rate 256 markers < 2 minutes
Accuracy Within 0.5 mm RMS
Stand-off 105 mm from the scanner
Depth of View 778 mm
Near field width 276 mm
Far field width 840 mm
Safety IEC 60601-1 3rd Edition
Legal Disclaimer
NDI tracking and measurement products (listed below) 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 use of NDI products or technologies in any application.