Evaluating a new generation of wearable high-density diffuse optical tomography technology via retinotopic mapping of the adult visual cortex

Abstract

Significance: High-density diffuse optical tomography (HD-DOT) has been shown to approach the resolution and localization accuracy of blood oxygen level dependent-functional magnetic resonance imaging in the adult brain by exploiting densely spaced, overlapping samples of the probed tissue volume, but the technique has to date required large and cumbersome optical fiber arrays. Aim : To evaluate a wearable HD-DOT system that provides a comparable sampling density to large, fiber-based HD-DOT systems, but with vastly improved ergonomics. Approach : We investigated the performance of this system by replicating a series of classic visual stimulation paradigms, carried out in one highly sampled participant during 15 sessions to assess imaging performance and repeatability. Results : Hemodynamic response functions and cortical activation maps replicate the results obtained with larger fiber-based systems. Our results demonstrate focal activations in both oxyhemoglobin and deoxyhemoglobin with a high degree of repeatability observed across all sessions. A comparison with a simulated low-density array explicitly demonstrates the improvements in spatial localization, resolution, repeatability, and image contrast that can be obtained with this high-density technology. Conclusions : The system offers the possibility for minimally constrained, spatially resolved functional imaging of the human brain in almost any environment and holds particular promise in enabling neuroscience applications outside of the laboratory setting. It also opens up new opportunities to investigate populations unsuited to traditional imaging technologies.

Wearable, Integrated EEG–fNIRS Technologies: A Review

“…Looking towards the future of EEG–fNIRS systems, investigations into ergonomic designs (i.e., wearable, miniaturized, lightweight, flexible) will continue to remain of key interest for long-term monitoring, wearability, and subject comfort. Improvements in resolution, high-speed ADCs, sensitive amplifiers, and precise logic control will be necessary to obtain the large dynamic range needed for high channel count fNIRS systems [ 8 , 62 , 63 , 64 ]. Consequently, more advanced data interfaces and control schemes would be required to ensure a large channel count, large dynamic range, and high-speed data acquisition and transmission.…”

“…Despite the success, the conformability (to the curved human scalp) and subject comfort of these electrodes still can be improved. Besides this, how to fit these relatively bulky electrodes into a miniaturized, compact wearable fNIRS module/functional blocks [ 8 , 61 , 62 , 63 ] remains unclear.…”

Investigation of effect of modulation frequency on high-density diffuse optical tomography image quality

“…The availability of CW-HD-DOT systems is increasing rapidly for both adult and pediatric studies owing to the demonstrated improvements in image quality obtained with HD arrays. 1 , 12 , 13 , 55 – 62 Most research groups still utilize CW systems for wide-field optical imaging of human brain function as these systems are significantly less expensive than FD and TD systems. However, recent studies have highlighted a renewed focused on HD arrangements of FD measurements due to the value in incorporating the additional phase measurements to realize the potential for improved image quality and potential access to absolute oxygenation concentration.…”

Transcranial Sonography in the Diagnosis of Pituitary Tumor—A Direct Comparison With MRI

“…Although MRI is the most widely used method to diagnose pituitary tumors, this technique is quite costly and time-consuming, especially since the pituitary gland requires specialized imaging sequences. In addition, MRI has contraindications for electronic or metal implants (such as pacemakers, cochlear implants, aneurysm clips, and surgical devices) ( 7 ) and claustrophobia.…”