Direct measurement of tissue blood flow and metabolism with diffuse optics

Abstract

Diffuse optics has proven useful for quantitative assessment of tissue oxy-and deoxyhaemoglobin concentrations and, more recently, for measurement of microvascular blood flow. In this paper, we focus on the flow monitoring technique: diffuse correlation spectroscopy (DCS). Representative clinical and pre-clinical studies from our laboratory illustrate the potential of DCS. Validation of DCS blood flow indices in human brain and muscle is presented. Comparison of DCS with arterial spin-labelled MRI, xenon-CT and Doppler ultrasound shows good agreement (0.50 < r < 0.95) over a wide range of tissue types and source detector distances, corroborating the potential of the method to measure perfusion non-invasively and in vivo at the microvasculature level. Alloptical measurements of cerebral oxygen metabolism in both rat brain, following middle cerebral artery occlusion, and human brain, during functional activation, are also described. In both situations, the use of combined DCS and diffuse optical spectroscopy/near-infrared spectroscopy to monitor changes in oxygen consumption by the tissue is demonstrated. Finally, recent results spanning from gene expression-induced angiogenic response to stroke care and cancer treatment monitoring are discussed.

Modified Beer-Lambert law for blood flow

“…Since early work with in-vitro phantoms and in-vivo tissues [15, 23- [39][40][41][42]. In addition, the DCS blood flow index has been successfully validated against a plethora of gold-standard techniques [3,43]. Several recent reviews highlight the theory, implementation and applications of DCS [1,3,13,14,44], and therefore our background discussion will be brief.…”

“…Diffuse optical techniques, such as near-infrared or diffuse optical spectroscopy (DOS, NIRS) and diffuse correlation spectroscopy (DCS), have been employed with remarkable success over the last two decades to probe hemodynamic processes in highly scattering tissues such as human brain, muscle and breast [1][2][3][4][5][6][7][8][9][10][11]. In total, this research has discovered new indicators of tissue function and health that are proving to be clinically relevant [6][7][8][9][10][11][12][13][14].…”

Photodynamic Therapy-Induced Microvascular Changes in a Nonmelanoma Skin Cancer Model Assessed by Photoacoustic Microscopy and Diffuse Correlation Spectroscopy

“…We used DCS to monitor changes in blood flow caused by PDT [16,[28][29][30][31][32][33][34][35]. Briefly, the DCS setup consisted of a long coherence length, 785 nm laser (CrystaLaser), four photon-counting detectors (Perkin Elmer, Waltham, MA, USA) and a custom-built autocorrelator board (Correlator.com).…”

Blood flow dynamics during local photoreaction in a head and neck tumor model

“…Empirically it has been observed in a broad range of studies at preclinical and clinical settings that diffusion model fits the autocorrelation curves better than random flow model and αD B characterizes the blood flow in deep tissue [40][41][42][43][44][45][46][47]. Here α is a factor representing the probability that a scattering event in tissue is from a moving scatterer (α is generally proportional to tissue blood volume fraction).…”