Functional imaging of the human brain using a modular, fibre-less, high-density diffuse optical tomography system

Abstract

We present the first three-dimensional, functional images of the human brain to be obtained using a fibre-less, high-density diffuse optical tomography system. Our technology consists of independent, miniaturized, silicone-encapsulated DOT modules that can be placed directly on the scalp. Four of these modules were arranged to provide up to 128, dual-wavelength measurement channels over a scalp area of approximately 60 × 65 mm2. Using a series of motor-cortex stimulation experiments, we demonstrate that this system can obtain high-quality, continuous-wave measurements at source-detector separations ranging from 14 to 55 mm in adults, in the presence of hair. We identify robust haemodynamic response functions in 5 out of 5 subjects, and present diffuse optical tomography images that depict functional haemodynamic responses that are well-localized in all three dimensions at both the individual and group levels. This prototype modular system paves the way for a new generation of wearable, wireless, high-density optical neuroimaging technologies.

Diffuse optical tomography reconstruction method using ultrasound images as prior for regularization matrix

“…These measurements are then used to estimate (recover) optical proprieties of the tissue. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Minimal light absorption in this wavelength range, allows for several centimeters of light penetration in soft tissue, such as breast and brain. 3 Utilizing multiple wavelengths in the NIR range enables this technology to quantify tissue characteristics, such as oxygenated, deoxygenated, and total hemoglobin (HbO2, HbR, and HbT) concentrations as well as hemoglobin oxygen saturation (SO 2 ) and lipid and water concentrations.…”

“…DOT is emerging in many fields, such as brain imaging, monitoring of cerebral hemodynamics, diagnosis of rheumatoid arthritis, breast cancer detection, and treatment monitoring. [6][7][8][9][10] In addition to all of the promising applications of the DOT, it has not been widely used in clinics because of strong light scattering in biological tissues. Light scattering causes poor spatial resolution and location uncertainty of reconstructed lesions.…”

Functional Near Infrared Spectroscopy: Enabling routine functional brain imaging

“…Instead, efforts focusing on developing wearable, fiberless systems have strived recently for higher spatial sampling density [18]. For instance, a recent modular DOT system offers the promise of combining high-density measurements with wearability [19] (Figure 2.d–f), and we envision that similar systems will be developed in the upcoming years to reconcile the needs of portability and spatial mapping accuracy.…”

“…The majority of wearable devices take advantage of light-emitting diodes (LEDs) and photodiodes [19] [20]. Early portable systems used electrical cables, more prone to RF interference, to transfer analog signals to a controller module [21][22], typically held in a backpack.…”

“…Early portable systems used electrical cables, more prone to RF interference, to transfer analog signals to a controller module [21][22], typically held in a backpack. More recent wearable systems implement digital conversion directly in the optode [19] [20]. These systems can be extremely light, but generally afford only low dynamic range on the detected signal, and restricted measurements to fixed source-detector separations and to forehead only.…”