Speckle contrast diffuse correlation tomography of complex turbid medium flow

Abstract

Purpose: Developed herein is a three-dimensional (3D) flow contrast imaging system leveraging advancements in the extension of laser speckle contrast imaging theories to deep tissues along with our recently developed finite-element diffuse correlation tomography (DCT) reconstruction scheme. This technique, termed speckle contrast diffuse correlation tomography (scDCT), enables incorporation of complex optical property heterogeneities and sample boundaries. When combined with a reflectance-based design, this system facilitates a rapid segue into flow contrast imaging of larger, in vivo applications such as humans. Methods: A highly sensitive CCD camera was integrated into a reflectance-based optical system. Four long-coherence laser source positions were coupled to an optical switch for sequencing of tomographic data acquisition providing multiple projections through the sample. This system was investigated through incorporation of liquid and solid tissue-like phantoms exhibiting optical properties and flow characteristics typical of human tissues. Computer simulations were also performed for comparisons. A uniquely encountered smear correction algorithm was employed to correct pointsource illumination contributions during image capture with the frame-transfer CCD and reflectance setup. Results: Measurements with scDCT on a homogeneous liquid phantom showed that speckle contrastbased deep flow indices were within 12% of those from standard DCT. Inclusion of a solid phantom submerged below the liquid phantom surface allowed for heterogeneity detection and validation. The heterogeneity was identified successfully by reconstructed 3D flow contrast tomography with scDCT. The heterogeneity center and dimensions and averaged relative flow (within 3%) and localization were in agreement with actuality and computer simulations, respectively. Conclusions: A custom cost-effective CCD-based reflectance 3D flow imaging system demonstrated rapid acquisition of dense boundary data and, with further studies, a high potential for translatability to real tissues with arbitrary boundaries. A requisite correction was also found for measurements in the fashion of scDCT to recover accurate speckle contrast of deep tissues. C 2015 American Association of Physicists in Medicine. [http://dx

Clinical applications of near-infrared diffuse correlation spectroscopy and tomography for tissue blood flow monitoring and imaging

“…Exploiting the high mathematical similarity of the forward and inverse problems (e.g., boundary conditions and mathematical assumptions) between DOT and DCT, our group first reported the application of FEM in DCT (Lin et al , 2014; Huang et al , 2015a; He et al , 2015; Huang et al , 2015b). We introduced this concept into the FEM-based light transport and image reconstruction modules in NIRFAST (Dehghani et al , 2009), as a shortcut for FEM implementation of DCT.…”

“…We introduced this concept into the FEM-based light transport and image reconstruction modules in NIRFAST (Dehghani et al , 2009), as a shortcut for FEM implementation of DCT. Specifically, we used the “ effective μ a ( r⃗ )” (i.e., ${\mu }_a(\overrightarrow{r})+2{\mu }_s^{\prime }(\overrightarrow{r})k_0^2\mathrm{\Delta }\alpha D_B(\overrightarrow{r})\tau$) and measured G 1 ( r⃗ , τ ) to replace the μ a ( r⃗ ) and photon fluence rate Φ( r⃗ , t ) respectively in the NIRFAST for the accomplishment of DCT in tissues with complex boundaries (Lin et al , 2014; Huang et al , 2015a; He et al , 2015; Huang et al , 2015b). Computer simulations, phantom tests, and in-vivo studies have verified the accuracy of our modifications of NIRFAST adapted for DCT.…”

“…With current ncDCT, the ROI must be mechanically scanned for a complete tissue coverage, which can take up to 40 minutes and may result in motion artifacts. To overcome these limitations, we recently developed and tested a non-scanning, noncontact, fast, portable, cost-effective device, namely speckle contrast diffuse correlation tomography (scDCT), for 3-D imaging flow distributions (Huang et al , 2015a; Huang et al , 2016). The scDCT used a charge-coupled-device (CCD) as a 2-D detector array to cover a ROI, thus eliminating the mechanical scanning and consequent problems.…”

“…An early contact-measurement based 3-D diffuse correlation tomography (DCT) approach using an optical fiber array was applied to tissue phantoms with a semi-infinite geometry (Boas and Yodh, 1997), but is disadvantaged in vivo due to the irregular geometries of biological tissues. A few noncontact-measurement based DCT examinations have been recently conducted to avoid tissue hemodynamic variations induced by the probe compression or the disturbance of sensitive tissue areas (Culver et al , 2003; Huang et al , 2015a; Zhou et al , 2006; Lin et al , 2014; He et al , 2015; Huang et al , 2015b). In these noncontact measurement systems, lenses were positioned between a sample and an optical fiber array connected to the light sources and detection elements.…”

Noncontact 3-D Speckle Contrast Diffuse Correlation Tomography of Tissue Blood Flow Distribution

“…Very recently, our group developed a reflectance diffuse speckle contrast tomography technique, namely speckle contrast DCT (scDCT) [13]. scDCT examines deep tissue blood flow by monitoring spatial (or temporal) diffuse speckle contrasts as opposed to correlation decay curves [13–18].…”