Noninvasive observation of skeletal muscle contraction using near-infrared time-resolved reflectance and diffusing-wave spectroscopy

Abstract

Abstract. We introduce a method for noninvasively measuring muscle contraction in vivo, based on near-infrared diffusing-wave spectroscopy ͑DWS͒. The method exploits the information about time-dependent shear motions within the contracting muscle that are contained in the temporal autocorrelation function g ͑1͒ ͑ , t͒ of the multiply scattered light field measured as a function of lag time, , and time after stimulus, t. The analysis of g ͑1͒ ͑ , t͒ measured on the human M. biceps brachii during repetitive electrical stimulation, using optical properties measured with time-resolved reflectance spectroscopy, shows that the tissue dynamics giving rise to the speckle fluctuations can be described by a combination of diffusion and shearing. The evolution of the tissue Cauchy strain e͑t͒ shows a strong correlation with the force, indicating that a significant part of the shear observed with DWS is due to muscle contraction. The evolution of the DWS decay time shows quantitative differences between the M. biceps brachii and the M. gastrocnemius, suggesting that DWS allows to discriminate contraction of fast-and slow-twitch muscle fibers.

Direct measurement of tissue blood flow and metabolism with diffuse optics

“…This problem is especially important for exercise experiments. While some progress has been made towards decreasing the magnitude of this problem by time-gating the measurements [31], a detailed analysis is needed to learn better how motion artefacts affect the signal and/or how assumptions in analysis schemes may be violated, when motion artefacts are present [32]. The influence of optical probe pressure is another important parameter that has yet to be fully considered.…”

“…Such effects will be small and can be accounted for by independent NIRS/DOS measurements. For the mean-square particle displacement, in practice, the Brownian model, Dr 2 (t) = 6D B t, fits the observed correlation decay curves fairly well over a wide range of tissue types and source-detector separations, including rat brain [18][19][20][21][22]; mouse tumours [23][24][25][26]; piglet brain [27]; and human skeletal muscle [28][29][30][31][32], human tumours [33][34][35][36][37][38][39] and human brain [40][41][42][43][44][45][46][47][48] (figure 1c). Here, D B is an effective diffusion coefficient that is a few orders of magnitude larger than the traditional thermal Brownian diffusion coefficient of cells in blood given by the Einstein-Smoluchowski relation [49].…”

Pulse wave analysis with diffusing-wave spectroscopy

“…One explanation for such a behavior is shearing of the surrounding tissue due to distention of the artery leading to additional contributions. The same effect is observed during muscle contraction [15] and can be used to reduce motion artifacts. Another explanation might be that the MSD ∆r 2 (τ) = 6D (2) τ + v 2 R BC τ 2 of the blood flow has both diffusive and directed contributions [12].…”

“…The mean squared displacement is fitted both with a simple diffusion model ( ∆r 2 (τ) = 6Dτ) and a mixed diffusion and shearing model ( ∆r 2 (τ) = 6D (2) τ + E (2) τ 2 ) [15,16]. The diffusion coefficient D (2) is proportional to blood flow [10][11][12] and E (2) accounts for any directed motion such as muscle movements [15]. The dominant term is given by the diffusion coefficient while the second gives an additional contribution during contraction and relaxation of the muscle.…”

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.…”