Low-cost compact diffuse speckle contrast flowmeter using small laser diode and bare charge-coupled-device

Abstract

We report a low-cost compact diffuse speckle contrast flowmeter (DSCF) consisting of a small laser diode and a bare charge-coupled-device (CCD) chip, which can be used for contact measurements of blood flow variations in relatively deep tissues (up to ∼ 8 mm). Measurements of large flow variations by the contact DSCF probe are compared to a noncontact CCD-based diffuse speckle contrast spectroscopy and a standard contact diffuse correlation spectroscopy in tissue phantoms and a human forearm. Bland–Altman analysis shows no significant bias with good limits of agreement among these measurements: 96.5%±2.2% (94.4% to 100.0%) in phantom experiments and 92.8% in the forearm test. The relatively lower limit of agreement observed in the in vivo measurements (92.8%) is likely due to heterogeneous reactive responses of blood flow in different regions/volumes of the forearm tissues measured by different probes. The low-cost compact DSCF device holds great potential to be broadly used for continuous and longitudinal monitoring of blood flow alterations in ischemic/hypoxic tissues, which are usually associated with various vascular diseases.

Noncontact speckle contrast diffuse correlation tomography of blood flow distributions in tissues with arbitrary geometries

“…This protocol has been extensively used for the validation of NIR instruments. 16,29,30 The forearm has sufficient space to image, and the cuff occlusion can be easily applied on the upper arm to create blood flow variations. Both PST and scDCT data were collected by the upgraded scDCT system.…”

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

“…Briefly, spatial speckle contrast detected by the EMCCD at the position r is defined as $$K_{s}false(\mathrm{bold-italicr}false)=\frac{{\sigma }_s}{\langle I\rangle }$$where σ s is the spatial standard deviation and 〈 I 〉 is the mean intensity in a pixel window of 7 × 7 pixels [1, 12, 13, 18, 20]. K s ( r ) is related to the normalized temporal electric field autocorrelation function g 1 ( r , τ ) [13, 14]: $$\left[K_s{(\mathit{r})}^2\right]=\frac{2\beta }{T}true{\int }_0^T\left(1-\frac{\tau }{T}\right)g_1^{2}false(\mathrm{bold-italicr},\tau false)d\tau$$where T is the EMCCD exposure time and τ is the correlation delay time.…”

“…scDCT examines deep tissue blood flow by monitoring spatial (or temporal) diffuse speckle contrasts as opposed to correlation decay curves [13–18]. APDs were replaced by a single highly sensitive electron-multiplying CCD (EMCCD) camera with zoom lens for rapid and inexpensive measurements.…”

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

“…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.…”