Multichannel time-resolved optical monitoring system was constructed for measurements of diffuse reflectance in optically turbid medium at very large source-detector separation up to 9 cm. The system is based on femtosecond TiSa laser and... more
Multichannel time-resolved optical monitoring system was constructed for measurements of diffuse reflectance in optically turbid medium at very large source-detector separation up to 9 cm. The system is based on femtosecond TiSa laser and sensitive photomultiplier tube detector. The laser light of 300mW of power was delivered to the surface of the head with the use of an optical fiber. A beam expander was applied in order to distribute the laser light on a large spot which allowed to avoid energetic stimulation of the tissue. The photomultiplier tube detector was positioned directly on the surface of the medium at the distance of 9cm from the center of the source position. In this paper we report results of an in-vivo experiment carried out on the head of an adult healthy volunteer. The time-resolved system was applied during intravenous injection of an optical contrast agent (indocyanine green - ICG) and the distributions of times of flight of photons were successfully acquired sho...
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Performance assessment of instruments devised for clinical applications is of key importance for validation and quality assurance. Two new protocols were developed and applied to facilitate the design and optimization of instruments for... more
Performance assessment of instruments devised for clinical applications is of key importance for validation and quality assurance. Two new protocols were developed and applied to facilitate the design and optimization of instruments for time-domain optical brain imaging within the European project nEUROPt. Here, we present the "Basic Instrumental Performance" protocol for direct measurement of relevant characteristics. Two tests are discussed in detail. First, the responsivity of the detection system is a measure of the overall efficiency to detect light emerging from tissue. For the related test, dedicated solid slab phantoms were developed and quantitatively spectrally characterized to provide sources of known radiance with nearly Lambertian angular characteristics. The responsivity of four time-domain optical brain imagers was found to be of the order of 0.1 m² sr. The relevance of the responsivity measure is demonstrated by simulations of diffuse reflectance as a funct...
Research Interests: Computer Science, Algorithms, Biomedical Engineering, Microscopy, Optical coherence tomography, and 11 moreBiomedical Optics, Brain, Europe, Mice, Animals, Optical physics, Optometry and Ophthalmology, Reproducibility of Results, Sensitivity and Specificity, Equipment Design, and Equipment Failure Analysis
The aim of this study was to evaluate enhancing of the depth sensitivity of time-resolved near-infrared spectroscopy with a subtraction-based approach. Due to the complexity of light propagation in a heterogeneous media, and to prove the... more
The aim of this study was to evaluate enhancing of the depth sensitivity of time-resolved near-infrared spectroscopy with a subtraction-based approach. Due to the complexity of light propagation in a heterogeneous media, and to prove the validity of the proposed method in a heterogeneous turbid media we conducted a broad analysis taking into account a number of parameters related to the method as well as various parameters of this media. The results of these experiments confirm that the depth sensitivity of the subtraction-based approach is better than classical approaches using continuous-wave or time-resolved methods. Furthermore, the results showed that the subtraction-based approach has a unique, selective sensitivity to a layer at a specific depth. In vivo application of the proposed method resulted in a greater magnitude of the hemodynamic changes during functional activation than with the standard approach.
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... I.: Mcml – monte carlo modeling of light transport in multi-layered tissues, Computer Methods & Programs in Biomedicine 1995, 47, 131–146. 27. Bresenham JE: Algorithm for computer control of a digital plotter. IBM Systems... more
... I.: Mcml – monte carlo modeling of light transport in multi-layered tissues, Computer Methods & Programs in Biomedicine 1995, 47, 131–146. 27. Bresenham JE: Algorithm for computer control of a digital plotter. IBM Systems Journal 1965, 4, 1, 25–30. 28. Bolin FP, Preuss LE ...
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Spectral analysis of high-resolution ECG based on fast Fourier transform and autoregressive estimation is discussed. The detectability of cardiac late potentials and prediction of ventricular tachyarrhythmias are compared using time and... more
Spectral analysis of high-resolution ECG based on fast Fourier transform and autoregressive estimation is discussed. The detectability of cardiac late potentials and prediction of ventricular tachyarrhythmias are compared using time and frequency analysis of ECG data of 120 patients after myocardial infarction. The quantification of spectrotemporal maps was proposed to simplify interpretation of results and to obtain numerical criteria for
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The in-vivo optical properties of the human head are investigated in the 600-1100 nm range on different subjects using continuous wave and time domain diffuse optical spectroscopy. The work was performed in collaboration with different... more
The in-vivo optical properties of the human head are investigated in the 600-1100 nm range on different subjects using continuous wave and time domain diffuse optical spectroscopy. The work was performed in collaboration with different research groups and the different techniques were applied to the same subject. Data analysis was carried out using homogeneous and layered models and final results were also confirmed by Monte Carlo simulations. The depth sensitivity of each technique was investigated and related to the probed region of the cerebral tissue. This work, based on different validated instruments, is a contribution to fill the existing gap between the present knowledge and the actual in-vivo values of the head optical properties.
ABSTRACT The aim of this study was applications of cerebrospinal fluid (CSF) NMR-based metabolic fingerprinting to amyotrophic lateral sclerosis (ALS) as possible early diagnostic tool. Two CSF sample categories were collected: 9 ALS... more
ABSTRACT The aim of this study was applications of cerebrospinal fluid (CSF) NMR-based metabolic fingerprinting to amyotrophic lateral sclerosis (ALS) as possible early diagnostic tool. Two CSF sample categories were collected: 9 ALS patients and 13 age-matched control patients (without neurological disease). Metabolic profile of the CSF was determined by high resolution proton NMR spectroscopy. For statistical analysis magnitudes of 33 signals of the NMR spectrum were selected. Partial least square discriminant analysis (PLS-DA) and orthogonal PLS-DA (OPLS-DA) modeling were used to find potential biomarkers of the disease. Those analyses showed that it was possible to distinguish the ALS patients from the control ones on the basis of the CSF metabolic profile. Significantly higher levels of metabolites observed in the patients with ALS may represent the state of anaerobic metabolism and excitotoxicity.
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We developed imaging system based on time-gated, intensified CCD camera which can be applied for evaluation of absorbing and fluorescent inclusions in optically turbid medium. The setup was validated in series of phantom experiments.... more
We developed imaging system based on time-gated, intensified CCD camera which can be applied for evaluation of absorbing and fluorescent inclusions in optically turbid medium. The setup was validated in series of phantom experiments. Absorbing and fluorescent inclusions located in optically turbid medium were detected and localized at the depth up to 20mm.
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ABSTRACT We report on a time-resolved instrument for diffuse NIR-reflectance topography of the adult head. First results will be presented of time-resolved monitoring of the motor cortex area during finger tapping.
ABSTRACT We report on monitoring of the passage of an indocyanine green (ICG) bolus through the brain and extracerebral tissue in healthy volunteers by means of time-resolved diffuse NIR-reflectance measurements.
Abstract A novel time-domain brain imager has been applied in motor and visual stimulation experiments. Analyzing time windows together with moments of measured time-resolved reflectance allowed us to separate superficial and cerebral... more
Abstract A novel time-domain brain imager has been applied in motor and visual stimulation experiments. Analyzing time windows together with moments of measured time-resolved reflectance allowed us to separate superficial and cerebral responses.
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It is believed that endothelial dysfunction may be a link between systemic and ocular dysregulation in glaucoma. The aim of this study was to evaluate peripheral vascular reactive hyperemia in response to occlusion test and to correlate... more
It is believed that endothelial dysfunction may be a link between systemic and ocular dysregulation in glaucoma. The aim of this study was to evaluate peripheral vascular reactive hyperemia in response to occlusion test and to correlate peripheral vascular findings with retrobulbar hemodynamics parameters in patients with normal-tension glaucoma. Forty-eight patients with normal-tension glaucoma (mean age 58.1 years, 38 women) and 40 control subjects (mean age 54.1 years, 36 women) were subjected to a brachial arterial occlusion test and color Doppler imaging (LOGIQ 9, GE Medical Systems) of the retrobulbar arteries. Finger hyperemia was assessed by using a 2-channel laser Doppler flowmeter (MBF-3D, Moor Instruments, Ltd.). Time parameters (time to peak flow, half-time of hyperemia, time of recovery) and amplitude parameters (maximum hyperemia response, biological zero) of the post-occlusive reactive hyperemia signal pattern as well as velocities and resistance index of the ophthalm...
In this paper we present validation of laser-Doppler spectrum decomposition procedure in estimation of speed distribution of particles. Decomposition method is based on assumption that measured laser-Doppler spectrum can be approximated... more
In this paper we present validation of laser-Doppler spectrum decomposition procedure in estimation of speed distribution of particles. Decomposition method is based on assumption that measured laser-Doppler spectrum can be approximated by linear combination of Doppler shift probability distributions calculated for different speeds of particles and anisotropy of light scattering in the medium. The Doppler shift probability distributions were calculated using Monte-Carlo simulations for Henyey-Greenstein scattering phase function. This decomposition method allows to obtain distribution of speeds of moving particles in the medium, not only average speed as it was possible in laser-Doppler perfusion monitors. Recently we reported that the method was positively verified on spectra generated for different speed distributions using Monte Carlo simulations. In this study we present results of application of the decomposition procedure in analysis of laser-Doppler spectra obtained in physic...
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The study of neurovascular coupling greatly benefits from combined measurements of neuronal and vascular signals. Two-step signal processing is developed to extract parameters describing the coupling. Using a magnetometer in an extremely... more
The study of neurovascular coupling greatly benefits from combined measurements of neuronal and vascular signals. Two-step signal processing is developed to extract parameters describing the coupling. Using a magnetometer in an extremely well shielded room a broadband magnetoencephalogram was simultaneously measured with time-resolved near-infrared spectroscopy during a motor activity paradigm. The raw MEG and NIRS data were denoised separately using independent component analysis. After averaging the resulting signals showed motor activity-related changes. The temporal correspondence between MEG and NIRS was assessed plotting a combined trajectory and calculating a cross-correlation. Compared to the MEG signal, at movement onset the NIRS signal showed an onset delay in the range of seconds. Multi-variate signal pre-processing followed by temporal delay estimates demonstrated the extraction of neurovascular coupling parameters.
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The purpose of this study was to investigate microvascular perfusion in insulin-dependent diabetic patients at various locations on the foot, and to determine which part of the foot is most sensitive to microangiopathic changes. All the... more
The purpose of this study was to investigate microvascular perfusion in insulin-dependent diabetic patients at various locations on the foot, and to determine which part of the foot is most sensitive to microangiopathic changes. All the parameters of postocclusive reactive hyperemia calculated from multichannel laser Doppler recordings were also evaluated to find the most valuable measure for diabetes examination. Our study involved 65 subjects divided into four subgroups: male and female controls, and male and female IDDM patients without overt complications. The measurements were performed with a multichannel laser Doppler perfusion monitor using surface probes located in the distal parts of the lower limbs. The occlusion test was performed using a cuff located on the limb above the knee. Multivariate discriminatory analysis was used to evaluate the data. The most valuable data were obtained by recordings from the laser-Doppler probes located on the hallex and the base of the litt...
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To improve the diagnostic power of high resolution electrocardiography for discriminating patients at risk of ventricular arrhythmias, new methods based on spectral analysis have been used in recent years. The purpose of this study was to... more
To improve the diagnostic power of high resolution electrocardiography for discriminating patients at risk of ventricular arrhythmias, new methods based on spectral analysis have been used in recent years. The purpose of this study was to evaluate the effectiveness of these methods for predicting the risk of ventricular tachycardia and ventricular fibrillation in patients after myocardial infarction. High resolution ECG were recorded in 129 post-infarction patients and 23 healthy volunteers. Of the post-infarction patients: 62 presented with ventricular tachycardia, 23 with ventricular fibrillation, while 44 had no clinically relevant arrhythmias. The ECG signals were recorded in three orthogonal X, Y, Z leads and averaged using cross-correlation method. Spectral analysis was performed by fast Fourier transform and the parametric modeling method with autoregressive model. Spectral analysis data were evaluated quantitatively by computing normality factor for FFT and spectral factor f...
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The Near Infrared Spectroscopy (NIRS) has been established as a non-invasive method for monitoring the oxygenation state of human brain at the bedside. This possible by observing spectral changes in the tissue caused by presence of... more
The Near Infrared Spectroscopy (NIRS) has been established as a non-invasive method for monitoring the oxygenation state of human brain at the bedside. This possible by observing spectral changes in the tissue caused by presence of oxygenated hemoglobin, deoxygenated hemoglobin and cytochrome aa3. In this paper the technical data of the NIRS instrument and its clinical application particularly in investigation of cerebral oxygenation and hemodynamic has been described.
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... In order to make these image processing software packages and patient administrative data base more ... imaging, laser Doppler flowmetry, and thermographic imaging for the assessment of bloodflow in human ... Ahn, HC, Nilsson, GE... more
... In order to make these image processing software packages and patient administrative data base more ... imaging, laser Doppler flowmetry, and thermographic imaging for the assessment of bloodflow in human ... Ahn, HC, Nilsson, GE & W?rdell, K. (1992) A new technique for intra ...
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ABSTRACT Time-resolved fluorescence measurements were carried out on the head during indocyanine green (ICG) injection. The ICG washout rate was estimated in patients with severe cerebral perfusion abnormalities.
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ABSTRACT Multi-wavelength detection of time-resolved diffuse reflectance signal was carried out in phantom experiments with dynamic inflow of ICG at different depths in a turbid media.
ABSTRACT Time-resolved, fluorescence tomography system for small animals imaging was constructed. The setup is based on time-gated intensified CCD camera and picosecond laser. Preliminary experiments on rat-phantom with fluorescent... more
ABSTRACT Time-resolved, fluorescence tomography system for small animals imaging was constructed. The setup is based on time-gated intensified CCD camera and picosecond laser. Preliminary experiments on rat-phantom with fluorescent inclusions were carried out
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Monitoring of microvascular blood perfusion provides very specific information on the proper function or malfunction of some internal organs, e.g. the pancreas and kidney. The laser Doppler method was used to measure microperfusion in the... more
Monitoring of microvascular blood perfusion provides very specific information on the proper function or malfunction of some internal organs, e.g. the pancreas and kidney. The laser Doppler method was used to measure microperfusion in the skin of the lower limb of diabetic patients and patients undergoing hemodialysis. This method offers non-invasive, real-time monitoring and is already accepted in many clinical experiments. The method and the laser Doppler instruments used are described. Special attention is paid to the investigation of microvascular abnormality in diabetes by using a multichannel laser Doppler system during postocclusive reactive hyperemia. The study group consisted of 41 diabetes and 24 healthy subjects with no history of family diabetes. The most valuable data were obtained from the probe located on the most distal part of the foot. Some hyperemic parameters (maximum of hyperemic response, time to peak flow) were significantly different for the diabetic group as comparing to the norm. In the microcirculation study during hemodialysis, three patients with kidney dysfunction were investigated. Increase in red blood cell velocity was observed, probably caused by better distribution of blood to the peripheral circulation.
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Postocclusive reactive hyperemia (PORH) was evaluated in three healthy volunteers and in three patients with different etiologies and suffering from peripheral arterial occlusive disease (PAOD). Three noninvasive methods were used:... more
Postocclusive reactive hyperemia (PORH) was evaluated in three healthy volunteers and in three patients with different etiologies and suffering from peripheral arterial occlusive disease (PAOD). Three noninvasive methods were used: transcutaneous oximetry (TcPO2), near-infrared spectroscopy (NIRS), and laser Doppler flowmetry (LDF). Changes in perfusion and oxygenation of tissue were measured on foot before, during, and after arterial occlusion on thigh. Numerical parameters were derived from measured signals for quantification of the PORH response. Results of all three methods provided distinction between healthy volunteers and patients. The experimental optical techniques of NIRS and LDF demonstrated more clearly than the well-established TcPO2 method the difference between healthy volunteers and patients. The dynamics of the PORH response proved to be a better indicator of peripheral vascular disorder than the amplitude of responses.
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Abstract Different approaches to discriminate between cerebral and extracerebral absorption changes are compared by means of diffusion and Monte-Carlo simulations and applied to functional stimulation experiments. The influence of... more
Abstract Different approaches to discriminate between cerebral and extracerebral absorption changes are compared by means of diffusion and Monte-Carlo simulations and applied to functional stimulation experiments. The influence of instrument response and ...
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Monte Carlo simulations are frequently used in mod- eling of light transport in turbid media. They allow precise de- scription of light transport, but require long computation time. Logarithmic and trigonometric functions evaluation, and... more
Monte Carlo simulations are frequently used in mod- eling of light transport in turbid media. They allow precise de- scription of light transport, but require long computation time. Logarithmic and trigonometric functions evaluation, and genera- tion of pseudorandom numbers are main − time consuming procedures in Monte Carlo calculations of light transport. In this paper, parallel Monte Carlo method with