A portable NIRScout system (NIRx Medical Technologies, LLC) is provided by the Waisman Brain Imaging Core (WBIC). This imaging system is intended for non-invasive transcranial near-infrared spectroscopy (NIRS) of blood perfusion dynamics in the human head. NIRScout performs dual-wavelength (760 nm and 850 nm) continuous-wave (CW) near infrared (NIR) diffuse tomographic measurements on large tissue structures at high sampling rates (up to 100 Hz). The NIRScout system uses low-power (5mW/wavelength) NIR light-emitting diode (LED) optodes to illuminate brain activity. The instrument uses parallel readout of avalanche photodiode (APD) detectors, which measure changes in the intensity of light detected. The changes in light intensity reveal the biological chromophore (e.g., hemoglobin) metabolism in the region underneath a paired light source and detector at a distance of 3-cm, with a spatial resolution about 1 cm.
The NIRx system at WBIC uses 16 LED light sources and 16 APD detectors. This configuration can be altered with purchase of other combinations of sources and detectors. The current configuration allows us to cover broad brain regions of interest on both the right and left hemispheres of an individual subject, or to perform hyper-scanning on two subjects simultaneously. The system comes with NIRx caps that come in different sizes, ranging from 42 cm to 48 cm for children above 2 years old and from 54 cm to 60 cm for adults. This allow us the flexibility to test subjects with different head sizes. Data collection is achieved using a software package provided by the NIRx company, the NIRStar software, which is installed on a laptop computer. All the peripherals needed for fNIRS testing are stored on a mobile cart.
Removal of artifact: As continuous-wave fNIRS system cannot distinguish between changes in blood metabolism from the superficial brain tissue (extracerebral) and from the deeper scalp (cerebral tissue), we have implemented the use of specialized light detectors developed by NIRx. When paired with light sources these detectors provide “short channels” that span 0.8-cm and are aimed to help measure the extracerebral components, thereby helping to reduce extracerebral components in the NIRS signal and improving neural signal to noise ratio.
For more information regarding the fNIRS system please reach out to Michael Anderle.