CAV-III Front Panel

CAV-III Rear Panel

The CAV-III Cortical Activity Viewing fNIRS System

The CAV-III Cortical Activity Viewer is a dual-wavelength absorption spectrometer optimized for fNIRS applications. The instrument achieves high sensitivity through patent-pending spread spectrum measurement technology, and yields high per-subject success rates via a unique hair-penetrating brush optode design. Tests have shown an average signal increase of 10x as compared to flat optodes, with no need to discard individual data sets.

Advanced Signal Processing

A new patent-pending signal processing architecture contributes to the high performance of the CAV-III. The system uses spread spectrum modulation methods to multiplex the multiple LED transmit signals. This is similar to the operation of a lock-in-amplifier (LIA). LIAs chop a single transmit signal to gain much higher SNR. MRRA Inc.'s system chops multiple signals simultaneously in a manner such that they can be de-multiplexed at the receiver while still maintaining the LIA's high SNR advantage. This is very similar to the modulation method used in the Military's GPS system and is the most common form of CDMA modulation used in cell phones. This breakthrough technology enables high-SNR fNIRS measurements using modest detectors.

Improved Optode Design

The most visible difference in MRRA Inc.'s technology is our optodes. Customer interviews revealed that fNIRS users discard up to 50% of their data sets because of low quality signals due to hair obscuration. To solve this problem we developed the hair penetrating optode. The optode uses thin fibers in a brushed arrangement to penetrate hair to make solid optical contact with the scalp. The optodes are also somewhat resistant to movement artifacts since the flexible brush fibers form a 'shock absorber' between the optode and the scalp. For more information on this technology, see our paper here.

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CAV-III System Specifications:

Sensitivity: > OD 9.7
Wavelengths: 700nm, 850 nm
LED Power: 5 mW optical power at scalp per LED
1 cm hemodynamic reference channel optional
Optodes: Up to 16 tx, 32 rx hair penetrating brush optodes
Possible Measurement Channels: 1024
Communications: Ethernet
Control Computer: Windows laptop, included
Power: Rechargeable NiMh Batteries, 6 VDC
Run Time: > 1.5 hours
Dimensions: approx 33 cm h x 27 cm w x 11 cm d
Battery Charger: 110/220 VAC
Sample Rate: 5 Hz
Optode Mounting: 6.35mm (1/4 inch) aperture

This instrument is for research purposes only. It is only for use by qualified researchers and under their direct supervision.

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