Diffuse correlation spectroscopy in the Fourier domain with holographic camera-based detection

Abstract

We present a new approach to Diffuse Correlation Spectroscopy (DCS) which overcomes the limited light throughput of single mode photon counting techniques, and operates with continuous wave illumination without disturbance from ambient light. Heterodyne holographic detection allows parallel measurement of the power spectrum of a fluctuating electric field across thousands of modes, from which we may directly compute flow parameters using a novel Fourier domain DCS model. Our detection and modelling strategy are rigorously validated by modulating the Brownian and flow components of an optical tissue phantom, demonstrating absolute measurements of the Brownian diffusion coefficient in excellent agreement with conventional methods. We demonstrate the feasability of in vivo measurement through the recovery of pulsatile flow rates measured in the human forearm.

Performance optimisation of a holographic Fourier domain diffuse correlation spectroscopy instrument

“…We have previously demonstrated that the SNR of our measurement does not scale linearly with the square root of the number of speckles detected when using a DC subtraction temporal filtering strategy [ 14 , 15 ], as is shown by the red dashed line in Fig. 6(b) for = 0.1 Hz.…”

“…Techniques including multispeckle detection strategies [ 3 , 6 , 7 ], time-domain DCS [ 8 ], DCS in the short-wave infrared region [ 9 , 10 ], interferometric approaches [ 4 , 11 , 12 ], and acousto-optic modulation [ 13 ] have all been proposed. Placing a particular emphasis on scalability, affordability, and robustness to ambient light, we have previously demonstrated a novel Fourier domain DCS (FD-DCS) instrument that makes use of heterodyne holographic camera-based detection, and which is capable of making in vivo pulsatile flow measurements [ 14 , 15 ]. The potential benefits of FD-DCS compared to conventional DCS are multiple: SNR that scales linearly with the square root of the number of camera pixels used, order of magnitude reduction in detector cost, robustness to the effects of ambient light, shot noise limited detection using off-axis holography [ 16 ], potential for detector scalability and sensor partitioning (which could facilitate tomographic and depth discrimination techniques [ 2 , 17 ]), and suitability to a range of design wavelengths (which could confer a further SNR advantage [ 9 ]).…”

Fourier domain diffuse correlation spectroscopy with heterodyne holographic detection

“…We also thank Biju Cletus for his helpful discussion on the optical properties of intralipid tissue phantoms. Portions of this work were previously presented at SPIE BiOS, 2020 [ 52 ], we thank SPIE for granting permission to reproduce material from these proceedings.…”

Diffuse Correlation Spectroscopy: A Review of Recent Advances in Parallelisation and Depth Discrimination Techniques

“…Indeed, as was depicted by Carp et al, the field has seen steady linear growth over the past 15 years, with more than 350 publications [8]. Techniques including multispeckle detection strategies [3,[9][10][11], time-domain DCS (TD-DCS) [12], DCS in the short-wave infrared region [13][14][15], interferometric approaches [5,[16][17][18][19], and acousto-optic modulation [20] have all been proposed. Reducing the cost and enhancing the performance of such systems will allow for more widespread clinical use.…”