MOCA: a systematic toolbox for designing and assessing modular functional near-infrared brain imaging probes

Abstract

. Significance : The expansion of functional near-infrared spectroscopy (fNIRS) systems toward broader utilities has led to the emergence of modular fNIRS systems composed of repeating optical source/detector modules. Compared to conventional fNIRS systems, modular fNIRS systems are more compact and flexible, making wearable and long-term monitoring possible. However, the large number of design parameters makes understanding their impact on a probe’s performance a daunting task. Aim : We aim to create a systematic software platform to facilitate the design, characterization, and comparison of modular fNIRS probes. Approach : Our software—modular optode configuration analyzer (MOCA)—implements semi-automatic algorithms that assist in tessellating user-specified regions-of-interest, in interconnecting modules of various shapes, and in quantitatively comparing probe performance using metrics, such as spatial channel distributions and average brain sensitivity of the resulting probes. There is also support for limited parameter sweeping capabilities. Results : Through several examples, we show that users can use MOCA to design and optimize modular fNIRS probes, study trade-offs between several module shapes, improve brain sensitivity in probes via module re-orientation, and enhance probe performance via adjusting module spatial layouts. Conclusion : Despite its simplicity, our modular probe design platform offers a framework to describe and quantitatively assess probes made by modules, opening a new door for the growing fNIRS user community to approach the challenging problem of module- and probe-parameter selection and fine-tuning.

Flexible-circuit-based 3-D aware modular optical brain imaging system for high-density measurements in natural settings

“…With this information, the computer can determine the spatial orientation of each module in the probe based on the connection topology and the master node can implement spatial multi-plexing patterns generated using the MOCA toolbox. 43…”

“…Source LEDs are grouped into spatial multiplexing group (SMG) based on their spatial distributions during the probe design phase using our MOCA toolbox. 43 LEDs within the same SMG can be illuminated simultaneously due to sufficient spatial separation, provided by the user when creating the probe, and negligible cross-talk while LEDs across SMGs are illuminated sequentially. This approach allows us to accelerate data acquisition by a factor referred to as spatial multiplexing ratio, or SMR, defined as the totally number of source LEDs in a probe divided by the number of SMGs.…”

“…Our open-source MATLAB toolbox for designing and optimizing modular fNIRS probes, 43 as used in this work, can be freely accessed at http://github.com/COTILab/MOCA.…”

Using preregistration as a tool for transparent fNIRS study design

“…Alternatively, procedures that allow for the design of an optode array with respect to anatomical landmarks (e.g., nasion, inion, and left and right preauricular points) and to the standard EEG 10 to 20 positions 96 , 97 are often applied. For this purpose, several software tools have been invented and validated by the fNIRS community [e.g., AtlasViewer, 106 Array Designer, 107 fNIRS optode location designer (fOLD), 108 dev-fOLD, 109 modular optode configuration analyzer (MOCA), 110 and simple and timely optode registration method for functional near-infrared spectroscopy (STORM-Net) 111 ].…”

Using preregistration as a tool for transparent fNIRS study design

“…Alternatively, procedures that allow the design of an optode array with respect to anatomical landmarks (e.g., nasion, inion, left and right preauricular points) and to the standard EEG 10-20 positions 74,75 are often applied. For this purpose, several software tools have been invented and validated by the fNIRS community (e.g., Atlas Viewer 81 , Array Designer 82 , fNIRS Optode Location Designer (fOLD) 83 , dev-fOLD 84 , MOCA 85 ).…”