Spread spectrum time-resolved diffuse optical measurement system for enhanced sensitivity in detecting human brain activity

Abstract

Spread spectrum time-resolved diffuse optical measurement system for enhanced sensitivity in detecting human brain activity," J. Biomed. Opt. Abstract. Diffuse optical spectroscopy (DOS) and imaging methods have been widely applied to noninvasive detection of brain activity. We have designed and implemented a low cost, portable, real-time one-channel timeresolved DOS system for neuroscience studies. Phantom experiments were carried out to test the performance of the system. We further conducted preliminary human experiments and demonstrated that enhanced sensitivity in detecting neural activity in the cortex could be achieved by the use of late arriving photons. © 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 dual-wavelength spread spectrum-based spectroscopic system For time-domain near-infrared diffuse optical imaging

“…The core idea behind spread spectrum techniques is that a signal of specific bandwidth can be spread in the frequency domain, resulting into a lower instantaneous power signal which makes use of the full bandwidth of the communication channel. This idea has been successfully applied to TD NIRS as an alternative to pulsed excitation [5][6][7][8] , aiming at overcoming some of the aforementioned instrumentational challenges of traditional TD systems. Following a spread spectrum-based approach in TD NIRS would allow us to use lower power sources for tissue excitation, such as VCSELs, which are significantly cheaper compared to traditional pulsed excitation lasers, and can be modulated constantly at very high speed rates.…”

“…However, TD NIRS systems, in contrast to CW instruments, are typically bulky and expensive, and employ sensitive optoelectronics that often inhibit translation of the technique beyond the research environment. Spread spectrum methods are being investigated in an attempt to overcome some of the challenges involved in using conventional pulsed laser sources and time-of-flight (ToF) technology [5][6][7][8] . Herein, we demonstrate characterisation and preliminary in vivo results of the first dual-wavelength instrument in literature that exploits a spread spectrum approach for TD NIRS measurements.…”

A spread spectrum approach to time-domain near-infrared diffuse optical imaging using inexpensive optical transceiver modules

“…So far, other research groups have demonstrated the benefits of spread spectrum techniques into TD NIR imaging by using either bulky PRBS generators [ 21 – 25 ] or FPGAs [ 26 ], programmed to generate PRBSs to modulate fast vertical-cavity surface-emitting lasers (VCSELs), as also shown in [ 27 ], where an FPGA was employed, in order to generate a dual-channel 2 10 -1 PRBS at 2.5Gb/s line rate. The core principle in [ 27 ] relies upon the modulation and demodulation of the produced PRBSs with a low-frequency reference signal, by means of an analogue modulator (AM), thermoelectrically cooled avalanche photodiodes and a data acquisition (DAQ) device, which eventually leads to a significant compromise with respect to the resolution of the system’s IRF and acquired TPSFs.…”

Voxel-based measurement sensitivity of spatially resolved near-infrared spectroscopy in layered tissues

“…CWS, which uses an adaptation of the Beer-Lambert law, is the simplest to apply and the most widely used. Recent TRS 5 using data processing methods and high-performance FDS 6 have been developed to measure scattering and absorption coefficients, but these systems have not been widely introduced to clinical tests because it is a complex and expensive system. Both SRS and CWS are simple and low-cost approaches to light radiation and detection and benefit from a high signal-tonoise ratio.…”