No abstract

A novel brush optode was designed and demonstrated to overcome poor optical contact with the scalp that can occur during functional near infrared spectroscopy (fNIRS) and imaging due to light obstruction by hair. The brush optodes were implemented as an attachment to existing commercial flat-faced (conventional) fiber bundle optodes. The goal was that the brush optodes would thread through hair and improve optical contact on subjects with dense hair. Simulations and experiments were performed to assess the magnitude of these improvements. FNIRS measurements on 17 subjects with varying hair colors (blonde, brown, and black) and hair densities (0–2.96 hairs/mm2) were performed during a finger tapping protocol for both flat and brush optodes. In addition to reaching a study success rate of almost 100% when using the brush optode extensions, the measurement setup times were reduced by a factor of three. Furthermore, the brush optodes enabled improvements in the activation signal-to-noise ratio (SNR) by up to a factor of ten as well as significant (p < 0.05) increases in the detected area of activation (dAoA). The measured improvements in SNR were matched by Monte Carlo (MC) simulations of photon propagation through scalp and hair. In addition, an analytical model was derived to mathematically estimate the observed light power losses due to different hair colors and hair densities. Interestingly, the derived analytical formula produced excellent estimates of the experimental data and MC simulation results despite several simplifying assumptions. The analytical model enables researchers to readily estimate the light power losses due to obstruction by hair for both flat-faced fiber bundles and individual fibers for a given subject.

Abstmd-It has proven desirable to use multistage etalons and resonators in lightwave communication systems. The design of these linear structures, however, is made difficult by the manner in which their transfer functions are nonlinear with respect to their composite reflection coefficients. If we interpret the etalons as discrete-time lattice filters, then z-transform techniques may be used to recursively synthesize filters with desirable properties. An algorithm is developed which can be used to design the arbitrary all-pole transfer functions in transmission, and the restricted class of pole-zero transfer functions in reflection, which are possible to implement with this architecture. We present some design examples such as notch, or channel-blocking, filters and flattop bandpass, or channel-passing, filters which are appropriate for frequency-division multiple access and wavelength-division multiplexed communications systems. The theory predicts, and we show experimentally, how these structures may be used to discriminate, or route, signals based on their modulated or coded characteristics.

Abstract. Sensorimotor cortex plasticity induced by constraint-induced movement therapy (CIMT) in six children (10.2 AE 2.1 years old) with hemiplegic cerebral palsy was assessed by functional near-infrared spectroscopy (fNIRS). The activation laterality index and time-to-peak/duration during a finger-tapping task and the resting-state functional connectivity were quantified before, immediately after, and 6 months after CIMT. These fNIRS-based metrics were used to help explain changes in clinical scores of manual performance obtained concurrently with imaging time points. Five age-matched healthy children (9.8 AE 1.3 years old) were also imaged to provide comparative activation metrics for normal controls. Interestingly, the activation time-to-peak/duration for all sensorimotor centers displayed significant normalization immediately after CIMT that persisted 6 months later. In contrast to this improved localized activation response, the laterality index and resting-state connectivity metrics that depended on communication between sensorimotor centers improved immediately after CIMT, but relapsed 6 months later. In addition, for the subjects measured in this work, there was either a trade-off between improving unimanual versus bimanual performance when sensorimotor activation patterns normalized after CIMT, or an improvement occurred in both unimanual and bimanual performance but at the cost of very abnormal plastic changes in sensorimotor activity. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

A true three-dimensional monitor is being developed for the direct display of three- (or higher-) dimensional information. The device is constructed of a three-dimensional array of pixels, actually voxels or volume elements, which in their quiescent state are transparent. When these elements are excited optically through a fiber-optic pigtail, they fluoresce. The sum of many fluorescing elements thus compose a three-dimensional image.