Abstract
Diffuse correlation spectroscopy (DCS), combined with time-resolved reflectance spectroscopy (TRS) or frequency domain spectroscopy, aims at path length (i.e. depth) resolved, non-invasive and simultaneous assessment of tissue composition and blood flow. However, while TRS provides a path length resolved data, the standard DCS does not. Recently, a time domain DCS experiment showed path length resolved measurements for improved quantification with respect to classical DCS, but was limited to phantoms and small animal studies. Here, we demonstrate time domain DCS for in vivo studies on the adult forehead and the arm. We achieve path length resolved DCS by means of an actively mode-locked Ti:Sapphire laser that allows high coherence pulses, thus enabling adequate signal-to-noise ratio in relatively fast (~1 s) temporal resolution. This work paves the way to the translation of this approach to practical in vivo use.
Highlights
Time domain near infrared spectroscopy, known as time-resolved reflectance spectroscopy (TRS), measures the distribution of photon path lengths in tissue to characterize the probed volume in terms of its wavelength dependent reduced scattering and absorption coefficients [1,2]
The small distortions of the early gates with respect to the late in the DH case are due to the contributions of instrument response function, the contributions of the photons that underwent a small number of scattering events and the finite gate width
The effects of these contributions are different depending on the position of the center of the gate with respect to the distribution of times of flight (DTOF) curve, which is a topic for future study
Summary
Time domain near infrared spectroscopy, known as time-resolved reflectance spectroscopy (TRS), measures the distribution of photon path lengths (or photon time-offlights) in tissue to characterize the probed volume in terms of its wavelength dependent reduced scattering ( μs ' ) and absorption ( μa ) coefficients [1,2]. Since the probability distribution for the maximum penetration depth moves towards deeper layers when photon time-of-flight increases [3], the contributions from deeper tissue volumes can be better separated from superficial ones if the longer path length (longer timeof-flight) photons are analysed This ability to path length-resolve is crucial for the clinical success of this technique for many scenarios such as neuro-monitoring and neuro-imaging due to overlaying extracerebral tissue contamination of the signals. Traditional DCS uses continuous wave (CW) lasers and it does not readily contain a way to separate or gate short and long path lengths in a similar manner as TRS
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
