Fiber-based multispeckle detection for time-resolved diffusing-wave spectroscopy: characterization and application to blood flow detection in deep tissue

Abstract

We present a technique for the measurement of temporal field autocorrelation functions of multiply scattered light with subsecond acquisition time. The setup is based on the parallel detection and autocorrelation of intensity fluctuations from statistically equivalent but independent speckles using a fiber bundle, an array of avalanche photodiodes, and a multichannel autocorrelator with variable integration times between 6.5 and 104 ms. Averaging the autocorrelation functions from the different speckles reduces the integration time in diffusing-wave spectroscopy experiments drastically, thus allowing us to resolve nonstationary scatterer dynamics with single-trial measurements. We present applications of the technique to the measurement of arterial and venous blood flow in deep tissue. We find strong deviations both of the shape and characteristic decay time of autocorrelation functions recorded at different phases of the pulsation cycle from time-averaged autocorrelation functions.

Speckle contrast optical tomography: A new method for deep tissue three-dimensional tomography of blood flow

“…Diffuse correlation spectroscopy (DCS) [3,10] based on similar physical principles as LSF and LDF but for deep tissues has been extended to three-dimensional tomography (diffuse correlation tomography (DCT) [11][12][13][14][15][16]). However DCT instrumentation is limited by fairly low signal-to-noise, low dynamic range in terms of detectable intensity and relatively expensive detectors that have kept the detector channel counts to less than ∼28 [17]. In this work, we present a new speckle contrast based tomographic approach-speckle contrast optical tomography (SCOT)-that provides efficient three-dimensional imaging of flow in turbid media that can be expanded to significantly large detector channel counts.…”

“…collecting photons of order 10,000 per second. Since SNR increases as the square root of number of speckles, obtaining significant benefits in SNR as well as the dynamic range by doing multi-speckle measurements [17] by employing a large number of detectors at a given spot on the tissue surface is not feasible for the type of dense sampling [20] that is desired for practical DCT applications.…”

Pulse wave analysis with diffusing-wave spectroscopy

“…Diffusing wave spectroscopy measurements were performed with a fiber-multispeckle setup described earlier [8]. Light from a diode laser (TOPTICA, TA100) operating at λ = 802nm is coupled into a multimode optical fiber to deliver light to the tissue surface.…”

“…Here we present a proof of principle study of the application of a relative new optical measurement technique, Diffusing Wave Spectroscopy (DWS) also known as Diffuse Correlation Spectroscopy [8][9][10][11][12], which measures blood flow non-invasively. We show that this technique provides accurate temporal profiles of the blood flow pulse wave when a fast measurement system is used.…”

Near-infrared diffuse correlation spectroscopy in cancer diagnosis and therapy monitoring

“…In nonmuscular tissues moving red blood cells (RBCs) inside vessels are primarily responsible for these fluctuations, but complications such as fiber shearing and motion artifacts can arise, especially in muscular tissues. 21,22 DCS provides several new attractive features for blood flow measurement in microvasculature, such as noninvasiveness, portability, 23 high temporal resolution (up to 100 Hz), 24 and relatively large penetration depth (up to several centimeters). [25][26][27] DCS can be easily and continually applied at the bedside in clinical rooms.…”