Comparing fNIRS Hemodynamics to fMRI Hemodynamics
Compared to fMRI, fNIRS has different advantages and disadvantages. While fMRI has become the gold standard for in vivo imaging of the human brain, fNIRS stands out for its portability and robustness to noise, bringing functional imaging into realistic environments. While limited by its inferior spatial resolution and penetration depth, fNIRS has a much higher temporal resolution than fMRI, allowing measurements of concentration changes in both oxygenated and deoxygenated hemoglobin.
It is therefore of interest to many researchers how NIRS compares to fMRI in studies of brain function. While concurrent fMRI and fNIRS measurements have been mostly aiming at validating fNIRS as newer technology and studying the spatial and temporal correlations between the fMRI BOLD signal and the concentration changes in oxygenated and deoxygenated hemoglobin, it is evident that combined fNRIS and fMRI can give new insights into brain function by overcoming some of their intrinsic limitations.
The optical nature of the NIRS signal and its robustness to motion, as well as the size and portability of fNIRS devices, makes fNIRS an ideal candidate for multimodality studies. fNIRS can efortlessly be combined with fMRI, EEG, TMS, tDSC and many other brain imaging modalities, without causing any measurement interferences.
Multimodal fNIRS-fMRI with NIRx systems
All NIRx NIRSport and NIRScout systems can be provided as MRI compatible modules, with sufficiently long optical fibers and MRI compatible optodes, for seamless installation in an MRI environment. Digital trigger inputs allow for fNIRS fMRI integration. Thanks to the modular design of NIRx devices, the number of NIRS sources and detectors can be customized based on the intended coverage.
Statistical results of OT (top row) and fMRI (bottom row) using right and left finger tapping. Note that the high activation is coded in blue (negative t-values) in the OT maps. The fMRI results show associated regions of the motor system (p<0.05, corrected).
Mehnert, J., Schmitz,C., Noller, H.E., Obrig, H., & Mueller, K. (2010) Simultaneous optical tomography (OT) and fMRI with and wothout task activation. Poster presented at the International Soviety for Magnetic Resonance Imaging (ISMRM), 18th Scientific Meeting, Stockhold, Sweden.
NIRScout is an ultra-compact fNIRS neuroimaging solution that offers the versatility and scalability to fit a broad range of research applications. For example, investigating motor sensory functions, traumatic brain injury, learning/attention disorders and brain computer interfaces.
NIRSport is the first freely configurable, wearable, multichannel NIRS imaging system to be used on any part of the head. This pocket-book sized device combines LED illumination and innovative active detection technology into a truly wearable brain imaging solution.