Towards next generation time-domain diffuse optics devices

Abstract

Diffuse Optics is growing in terms of applications ranging from e.g. oximetry, to mammography, molecular imaging, quality assessment of food and pharmaceuticals, wood optics, physics of random media. Time-domain (TD) approaches, although appealing in terms of quantitation and depth sensibility, are presently limited to large fiber-based systems, with limited number of source-detector pairs. We present a miniaturized TD source-detector probe embedding integrated laser sources and single-photon detectors. Some electronics are still external (e.g. power supply, pulse generators, timing electronics), yet full integration on-board using already proven technologies is feasible. The novel devices were successfully validated on heterogeneous phantoms showing performances comparable to large state-of-the-art TD rackbased systems. With an investigation based on simulations we provide numerical evidence that the possibility to stack many TD compact source-detector pairs in a dense, null source-detector distance arrangement could yield on the brain cortex about 1 decade higher contrast as compared to a continuous wave (CW) approach. Further, a 3-fold increase in the maximum depth (down to 6 cm) is estimated, opening accessibility to new organs such as the lung or the heart. Finally, these new technologies show the way towards compact and wearable TD probes with orders of magnitude reduction in size and cost, for a widespread use of TD devices in real life.

Comparison of cerebral metabolic rate of oxygen, blood flow, and bispectral index under general anesthesia

“…In literature, TRS methods were proved to intrinsically provide deeper tissue information than CW-based ones. 49,111,135 We also acknowledge that nowadays two-layers analysis or moments-based methods can be used to ensure deeper tissue information assessment. 136,137 The need for CMRO 2 is an important, yet an unsettled question.…”

New frontiers in time-domain diffuse optics, a review

“…37 Still, TD NIRS will bring absolute quantitation and increased depth penetration, which are two limiting factors in typical NIRS approaches. 194 As discussed, new chip-based photonic components, such as the pulsed VCSEL as source, SIPM for detector, and CMOS TDC, are perfect ingredients for smart wearable devices to be used in brain monitors or muscle oximeters. 3.1), InGaAs detectors (see Sec.…”