Estimating the spatial resolution of fNIRS sensors for BCI purposes

Rand Kasim Almajidy; Robert D. Kirch; Olaf Christ; Ulrich G. Hofmann

doi:10.1117/12.2037351

3 March 2014 Estimating the spatial resolution of fNIRS sensors for BCI purposes

Rand Kasim Almajidy, Robert D. Kirch, Olaf Christ, Ulrich G. Hofmann

Proceedings Volume 8945, Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue VI; 894504 (2014) https://doi.org/10.1117/12.2037351
Event: SPIE BiOS, 2014, San Francisco, California, United States

Abstract

Differential near infrared sensors recently sparked a growing interest as a promising measuring modality for brain computer interfacing. In our study we present the design and characterization of novel, differential functional NIRS sensors, intended to record hemodynamic changes of the human motor cortex in the hand-area during motor imagery tasks. We report on the spatial characterization of a portable, multi-channel NIRS system with one module consisting of two central light emitting diodes (LED) (770 nm and 850 nm) and four symmetric pairs of radially aligned photodiodes (PD) resembling a plus symbol. The other sensor module features four similar, differential light paths crossing in the center of a star. Characterization was performed on a concentric, double beaker phantom, featuring a PBS/intralipid/blood mixture (97/1/2%). In extension of previous work, the inner, oxygenated beaker was covered by neoprene sleeves with holes of various sizes, thus giving an estimate on the spatial limits of the NIRS sensor’s measurement volume. The star shaped sensor module formed a diffuse focus of approximately 3 cm in diameter at 1.4 cm depth, whereas the plus shaped arrangement suggested a concentric ring of four separate regions of interest, overall larger than 6 cm. The systems measurement sensitivity could be improved by removing ambient light from the sensing photodiodes by optical filtering. Altogether, we conclude that both our novel fNIRS design as well as its electronics perform well in the double-layered oxygenation phantom and are thus suitable for in-vivo testing.

Citation Download Citation

Rand Kasim Almajidy, Robert D. Kirch, Olaf Christ, and Ulrich G. Hofmann "Estimating the spatial resolution of fNIRS sensors for BCI purposes", Proc. SPIE 8945, Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue VI, 894504 (3 March 2014); https://doi.org/10.1117/12.2037351

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available