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Portalite wireless cerebral NIRS (9)
This is really dependent on the signal quality. Typically for normal cortical penetration you will want anywhere from 3cm up, the larger the distance the deeper the penetration however at the sake of a reduced signal-to-noise ratio. Typically for normal adults we employ a 3.5cm interoptode distance, for those with darker skin or dark/dense hair you may need to reduce this to achieve an ideal SNR. For younger children and infants often times 2.5cm is more common.
Lasers often require greater consideration in application. There are certainly constraints with regard to motility with a laser based setup that may not be of any concern with LED. Preparation times are often greater with laser than LED, as lasers are often added to a headcap one by one, whereas LED sources could sometimes be “pre-populated”.
Lasers naturally provide a very focal output and are excellent with narrow band frequency emission, thus the ability to discretely “tune” the light output is perhaps of some value, as you might imagine when studying the dispersion of light. Additionally modulation of lasers can take place many times fast than that of LED, as there are some capacitive “left-overs” with LED
fNIRS is of course a completely different modality than fMRI, however while the mechanics may differ there is overlap in the resulting measurements, ultimately cerebral blood flow and metabolic measurements may be obtained, and neuronal activation often assumed. fNIRS is specific to oxygenated and deoxygenated hemoglobin measurement and quantification due to light back reflection, while fMRI aligns the orientation of the hemoglobin depending on the presence of oxygen. fNIRS offers a much better temporal resolution often 100x or more, while spatially fMRI has the upper hand by roughly 10x.
Very good, and important, question. Clearly fNIRS is employing frequencies of light that are purposely used to traverse the skull without much restraint, and this is in fact introducing exogenous stimuli. Well don’t fret, the amount of signal power using fNIRS can be comparable to sunlight. Further, of recent, several studies suggest there are various health benefits to infrared light stimulation at the cellular/metabolic level- even still these studies primarily employ chronic use.
This is a tough one, inherently hair is the nemesis of any fNIRS device on the market and while we all would like to say we have this completely figured out it ultimately comes down to proper preparation, part of which is also a skill in performing. I would use the same criteria with regard screening as you may normally do with EEG.
OxySoft is developed for use with Windows 7 or 10, both are supported however Windows 7 is still preferred. We also offer a free Android application for the PortaLite and PortaMon units for streaming and data logging.
Yes, you may stream up to 7 devices, both wired (OxyMon), and wireless devices (Brite 23, PortaMon/PortaLite) to the same acquisition PC in real time.