Improved calibration procedure for laser Doppler perfusion monitors

Fredriksson, Ingemar; Larsson, Marcus; Salomonsson, F.; Strömberg, Tomas

doi:10.1117/12.871938

Cited by 12 publications

(10 citation statements)

References 14 publications

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“…The LDF spectra were normalized with the total spectral power of that calibration measurement. In that way, the power in the measured LDF spectra can be directly compared to the power in the simulated LDF spectra [20]. The conventional perfusion measure was calculated as the sum of the frequency weighted LDF spectrum, i.e.…”

Section: Data Preprocessingmentioning

confidence: 99%

Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment

Jonasson

Fredriksson

Pettersson

et al. 2015

Microvascular Research

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We have developed a new fiber-optic system that combines diffuse reflectance spectroscopy (DRS) and laser Doppler Flowmetry (LDF) for a multi-modal assessment of the microcirculation. Quantitative data is achieved with an inverse Monte Carlo algorithm based on an individually adaptive skin model. The output parameters are calculated from the model and given in absolute units: hemoglobin oxygen saturation (%), red blood cell (RBC) tissue fraction (%), and the speed resolved RBC perfusion separated into three speed regions; 0-1 mm/s, 1-10 mm/s and above 10 mm/s (% mm/s). The aim was to explore microcirculatory parameters using the new optical method, integrating DRS and LDF in a joint skin model, during local heating of the dorsal foot and venous and arterial occlusion of the forearm in 23 healthy subjects (age 20-28 years). There were differences in the three speed regions in regard to blood flow changes due to local heating, where perfusion for high speeds increased the most. There was also a high correlation between changes in oxygenation and changes in perfusion for higher speeds. Oxygen saturation at baseline was 44% on foot, increasing to 83% at plateau after heating. The larger increase in perfusion for higher speeds than for lower speeds together with the oxygenation increase during thermal provocation, shows a local thermoregulatory blood flow in presumably arteriolar dermal vessels. In conclusion, there are improved possibilities to assess microcirculation using integrated DRS and LDF in a joint skin model by enabling both oxygenation and speed resolved blood flow assessment simultaneously and in the same skin site. Output parameters in absolute units may also yield new insights about the microcirculatory system.

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Section: Data Preprocessingmentioning

confidence: 99%

Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment

Jonasson

Fredriksson

Pettersson

et al. 2015

Microvascular Research

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“…or with the concentration of moving red blood cells (CMBC) value (the zero order moment of the Doppler spectrum) [105] scatt noise scatt…”

Section: Ldf Calibrationmentioning

confidence: 99%

“…By calibrating with CMBC instead of with the perfusion value, the calibration procedure is insensitive to the velocity of the moving scattering particles, to the temperature of the calibration solution and to the properties of the solution [105].…”

Section: Ldf Calibrationmentioning

confidence: 99%

Model-based quantitative assessment of skin microcirculatory blood flow and oxygen saturation

Jonasson¹

2016

Linköping Studies in Science and Technology. Dissertations

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The microcirculation, involving the smallest vessels in the body, is where the oxygen transport to all tissue occurs. Evaluating microcirculatory parameters is, therefore, important and involves the quantification of oxygen content of red blood cells (RBCs), the amount of RBCs and their speed.Diffuse reflectance spectroscopy (DRS) can be used to estimate blood oxygen saturation and fraction of RBCs in tissue since oxygenated and deoxygenated blood have different light absorption characteristics. By illuminating the skin with white light and detecting the spectrum of the backscattered light, tissue absorption and scattering can be assessed. Laser Doppler flowmetry (LDF) is a technique to measure blood flow in tissue. When laser light encounter moving objects in tissue, i.e. RBCs, the light is Doppler shifted, which can be detected and used to calculate tissue perfusion (the fraction of moving RBCs times their speed). With a small distance between light source and detector, both techniques measure superficially where most vessels are microcirculatory vessels. Photon transport in tissue can be simulated with Monte Carlo techniques and the simulations form the basis of modeled DRS and LDF spectra. The estimated microcirculatory parameters are given by the model that best describe measured DRS and LDF data.This thesis describes the development and the evaluation of an optical method to simultaneously measure oxygen saturation, RBC tissue fraction and speed resolved perfusion in absolute units by integrating DRS and LDF. By combining DRS and LDF into one system with a common tissue model, the two modalities can benefit from each other's strengths. Different calibration methods and model assumptions for the system were evaluated in optical phantoms and in skin measurements. A simple calibration method with two detector distances for DRS was found adequate to accurately estimate absorption and scattering in optical phantoms. It was also necessary to model blood located in vessels, rather than homogeneously distributed in the skin, to obtain accurate parameter estimates. The system was evaluated in healthy subjects during standard provocations, where the parameters were in agreement with other studies and followed an expected pattern during the provocations. In patients with diabetes type 2, tissue fraction of RBCs and nutritive blood flow were reduced in baseline compared to healthy controls. These differences were not related to prevalence of microalbuminuria, a marker sign of microvascular complications in the kidneys.A combined system with DRS and LDF enables a more comprehensive assessment of the microcirculation by measuring oxygen saturation, RBC tissue fraction and speed resolved perfusion simultaneously and in absolute units. This system has clinical potential to assist in the evaluation of the microcirculation both in healthy and diseased individuals. POPULÄRVETENSKAPLIG SAMMANFATTNINGMikrocirkulationen innefattar de minsta kärlen i kroppen och det är här syretransporten till all vävnad i kroppen sker. ...

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“…The latter issue is solved in the presented method by the relaxations in Eqs. (20) and (21) for DRS and by the previously presented calibration process 27 for LDF. The time resolution issues, both for acquiring high-quality spectra and for solving the inverse problem, may be a limiting factor in some specialized high-dynamic measurement situations.…”

Section: (B) (A)mentioning

confidence: 99%

“…Finally, the spectra were normalized with the first-order moment of a spectrum originating from a measurement in motility standard. This calibration routine is described in detail elsewhere 27 and results in intensity and frequency-calibrated spectra that can be compared with the spectra calculated from the model.…”

Section: In Vivo Measurementsmentioning

confidence: 99%

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry

Fredriksson¹,

et al. 2013

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Abstract. The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC × mm∕s), and more accurate due to the combination with DRS. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Improved calibration procedure for laser Doppler perfusion monitors

Cited by 12 publications

References 14 publications

Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment

Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment

Model-based quantitative assessment of skin microcirculatory blood flow and oxygen saturation

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry

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