Lightweight sCMOS-based high-density diffuse optical tomography

Abstract

Though optical imaging of human brain function is gaining momentum, widespread adoption is restricted in part by a tradeoff among cap wearability, field of view, and resolution. To increase coverage while maintaining functional magnetic resonance imaging (fMRI)-comparable image quality, optical systems require more fibers. However, these modifications drastically reduce the wearability of the imaging cap. The primary obstacle to optimizing wearability is cap weight, which is largely determined by fiber diameter. Smaller fibers collect less light and lead to challenges in obtaining adequate signal-to-noise ratio. Here, we report on a design that leverages the exquisite sensitivity of scientific CMOS cameras to use fibers with smaller cross-sectional area than current high-density diffuse optical tomography (HD-DOT) systems. This superpixel sCMOS DOT (SP-DOT) system uses -diameter fibers that facilitate a lightweight, wearable cap. We developed a superpixel algorithm with pixel binning and electronic noise subtraction to provide high dynamic range ( ), high frame rate ( ), and a low effective detectivity threshold ( ), each comparable with previous HD-DOT systems. To assess system performance, we present retinotopic mapping of the visual cortex ( subjects). SP-DOT offers a practical solution to providing a wearable, large field-of-view, and high-resolution optical neuroimaging system.

High-density speckle contrast optical tomography of cerebral blood flow response to functional stimuli in the rodent brain

“…For example, it allows the collection of highly dense data at multiple locations with lesser mechanical limitations such as those due to the location and the physical diameter of the fiber cladding. 30 However, noncontact measurements have limitations and we note here, that contact measurements can be implemented with SCOT, 30,52 which would allow for measurements through the hair when translating to studies on humans. 30 Other implementations can also be envisioned combining spatial, spectral, and temporal information efficiently.…”

Scalable, modular continuous wave functional near-infrared spectroscopy system (Spotlight)

“…This metric can be thought of as the noise density at 1 Hz and has the units W/rtHz. Note that this noise figure is different from the device-level NEP commonly presented in avalanche photodiodes (APD)-based fNIRS devices, 34 taking into account noise effects from the SiPM device, optode assembly, and system operation. 3.…”

“…The average coupling efficiency of the detector ferrule, which measures the percentage of optical power transmitted to the detector via the ferrule, was 11%. Detector SiPM NEP was calculated from datasheet values to be 1.27 fW-rms (850 nm) and 0.77 fW-rms (680 nm), translating to detectivity 34 of 40.4 and 24.5 fW-rms/mm2 (see Sec. 1.3 in the Supplementary Material).…”

Decoding visual information from high-density diffuse optical tomography neuroimaging data

“…Decoding in other populations, such as infants and patients with neurological disorders who have participated in prior fNIRS decoding studies ( Abdalmalak et al, 2017 ; Emberson et al, 2017 ), will present additional data acquisition challenges such as increased levels of motion and the need for imaging at the bedside. However, previous HD-DOT brain mapping studies have already established the feasibility of imaging at the bedside in neonates and stroke patients ( Culver et al, 2016 ; Ferradal et al, 2016 ; Liao et al, 2012 ), while newer lightweight ( Bergonzi et al, 2018 ) or fiber-less ( Zhao and Cooper, 2017 ) designs will further increase portability and reduce motion artifacts facilitating decoding studies in such populations.…”