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Time-resolved multi-channel optical system for assessment of brain oxygenation and perfusion by monitoring of diffuse reflectance and fluorescence

Milej D., Gerega A., Kacprzak M., Sawosz P., Weigl W., Maniewski R., Liebert A.

Opto-Electronics Review

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2014

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Vol. 22, No. 1

55-67

EN

Time-resolved near-infrared spectroscopy is an optical technique which can be applied in tissue oxygenation assessment. In the last decade this method is extensively tested as a potential clinical tool for noninvasive human brain function monitoring and imaging. In the present paper we show construction of an instrument which allows for: (i) estimation of changes in brain tissue oxygenation using two-wavelength spectroscopy approach and (ii) brain perfusion assessment with the use of single-wavelength reflectometry or fluorescence measurements combined with ICG-bolus tracking. A signal processing algorithm based on statistical moments of measured distributions of times of flight of photons is implemented. This data analysis method allows for separation of signals originating from extra- and intracerebral tissue compartments. In this paper we present compact and easily reconfigurable system which can be applied in different types of time-resolved experiments: two-wavelength measurements at 687 and 832 nm, single wavelength reflectance measurements at 760 nm (which is at maximum of ICG absorption spectrum) or fluorescence measurements with excitation at 760 nm. Details of the instrument construction and results of its technical tests are shown. Furthermore, results of in-vivo measurements obtained for various modes of operation of the system are presented.

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Time-resolved reflectometry and spectroscopy for assessment of brain perfusion and oxygenation

Liebert A., Kacprzak M., Maniewski R.

Biocybernetics and Biomedical Engineering

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2007

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Vol. 27, no. 1-2

217-225

EN

Time-resolved optical methods and instrumentation for non-invasive assessment of the cerebral cortex perfusion and oxygenation are presented. The oxygenation can be calculated using the moments of the distributions of times of flight of photons measured at two wavelengths in the near infrared region. For assessment of the brain perfusion, the kinetics of the inflow and washout of an exogenous dye injected intravenously is analyzed. The instrument developed at the Institute of Biocybernetics and Biomedical Engineering PAS is equipped with picosecond diode lasers, fast photodetectors and time correlated single photon counting electronics for acquisition of the distributions of times of flight of photons. This technique allows for a depth-resolved estimation of the changes of absorption and, in consequence, for an assessment of the changes occurring in the cerebral cortex. Combination of the data from multiple sources and detectors placed on the surface of the head with the depth-resolved analysis based on the moments enables to obtain images of the cortex perfusion and/or oxygenation. Potential applications of the instrument and its limitations are also discussed.

3

Validity of MRI brain perfusion imaging method

Karczewski B., Rumiński J.

Journal of Medical Informatics & Technologies

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2006

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Vol. 10

55--61

EN

Brain perfusion imaging using Dynamic Susceptibility Contrast Magnetic Resonance Imaging is very promising method since it can be easily implemented as a standard contrast-based MRI procedure. Quantitative brain perfusion description by DSC-MRI data post processing requires validation. Different validation analysis was performed to verify the influence of a bolus dispersion, delay, low SNR and calculation procedures on final perfusion parameter values. The results indicate that quantitative description of brain perfusion using DSC-MRI is possible and can be acceptable with accuracy about 10%.