Michal Kacprzak

• PhD
• PostDoc Position at Institute of Biocybernetics and Biomedical Engineering

Significance A shortcoming of the routine clinical use of diffuse optics (DO) in the injured head has been that the results from commercial near-infrared spectroscopy-based devices are not reproducible, often give physiologically invalid values, and differ among systems. Besides the limitations due to the physics of continuous-wave light sources, o...

Time-domain diffuse correlation spectroscopy (td-DCS) enables the depth discrimination in tissue’s blood flow recovery, considering the fraction of photons detected with higher time of flight (TOF) and longer pathlength through the tissue. However, the recovery result depends on factors such as the instrument response function (IRF), analyzed TOF g...

Background: Red blood cells transfusions (RBCT) are utilized to restore normal values of hemoglobin concentration and hematocrit percentage in anemic patients. As expected, RBCT often leads to local and global alteration of blood flow (BF) and blood/tissue oxygenation which could have local deleterious consequences. This complicates its use and its...

Hyperventilation (HV) can lower intracranial pressure to prevent secondary injuries in traumatic brain injury patients. Hybrid diffuse optics can detect misery perfusion, precursor of ischemia, to help guiding personalized therapy during HV. 22/27 measurement sessions (18 patients) showed MP risk.

[This corrects the article DOI: 10.1117/1.NPh.9.4.045005.].

Research on the spatial distribution of sensitivity of time-domain near infrared diffuse reflectance measurement is reported in this paper. The main objective of the investigation is to validate theoretically calculated sensitivity profiles for a measurement geometry with two detectors and two sources in which sensitivity profiles of statistical mo...

Hyperventilation (HV) therapy uses vasoconstriction to reduce intracranial pressure (ICP) by reducing cerebral blood volume. However, as HV also lowers cerebral blood flow (CBF), it may provoke misery perfusion (MP) where the decrease in CBF is coupled with increased oxygen extraction fraction (OEF). MP may rapidly lead to the exhaustion of brain e...

Significance: The optical measurement of cerebral oxygen metabolism was evaluated. Aim: Compare optically derived cerebral signals to the electroencephalographic bispectral index (BIS) sensors to monitor propofol-induced anesthesia during surgery. Approach: Relative cerebral metabolic rate of oxygen ( rCMRO 2 ) and blood flow (rCBF) were measu...

Significance: Benign external hydrocephalus (BEH) is considered a self-limiting pathology with a good prognosis. However, some children present a pathological intracranial pressure (ICP) characterized by quantitative and qualitative alterations (the so-called B-waves) that can lead to neurological sequelae. Aim: Our purpose was to evaluate wheth...

Significance: Multi-laboratory initiatives are essential in performance assessment and standardization-crucial for bringing biophotonics to mature clinical use-to establish protocols and develop reference tissue phantoms that all will allow universal instrument comparison. Aim: The largest multi-laboratory comparison of performance assessment in...

This poster presents the results of validation tests of a new multi-channel wearable functional near-infrared spectroscopy device (fNIRS). The device has 16 emitters and 10 detectors forming up to 37 channels. A continuous-wave principle of operation is used. We evaluated the ability of this device to measure the hemodynamic properties of the human...

Hybrid device for the study of blood flow index and hemoglobins concentrations changes was developed. Diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy were applied to study brain hemodynamics of healthy adults human during the Valsalva maneuver.

The blood flow is responsible for distributing nutrients and oxygen to all organs in the body. Any disorders in blood flow may lead to irreversible diseases or injuries. So, modalities for perfusion measurements would be essential at the clinical sites, especially in monitoring patients with cerebral blood flow (CBF) impairments. On the other hand,...

Performance assessment and standardization are indispensable for instruments of clinical relevance in general and clinical instrumentation based on photon migration/diffuse optics in particular. In this direction, a multi-laboratory exercise was initiated with the aim of assessing and comparing their performances. 29 diffuse optical instruments bel...

Monitoring of human tissue hemodynamics is invaluable in clinics as the proper blood flow regulates cellular-level metabolism. Time-domain diffuse correlation spectroscopy (TD-DCS) enables noninvasive blood flow measurements by analyzing temporal intensity fluctuations of the scattered light. With time-of-flight (TOF) resolution, TD-DCS should deco...

Hybrid device for the study of blood flow index and hemoglobins concentrations changes was developed. Diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy were applied to study brain hemodynamics of healthy adults human during the Valsalva maneuver.

A multi-laboratory exercise, involving 29 diffuse optical instruments, aimed at performance assessment of diffuse optics instruments on standardized protocols is presented. The overarching methodology and future actions will also be discussed.

A methodology for the assessment of the cerebral hemodynamic reaction to normotensive hypovolemia, reduction in cerebral perfusion and orthostatic stress leading to ischemic hypoxia and reduced muscular tension is presented. Most frequently, the pilots of highly maneuverable aircraft are exposed to these phenomena. Studies were carried out using th...

We evaluated the properties of oscillations in the Mayer waves (MW) frequency range ( ∼ 0 . 1 Hz) detected in blood pressure, heart rate variability, cerebral blood oxygenation changes and evolution of electroencephalographic (EEG) rhythms to elucidate the mechanisms of MW generation. We examined the persistence of MW in different signals and stab...

An intra-abdominal pressure (IAP) is correlated with cerebral perfusion, in a mechanism of reducing venous outflow. The elevated intra-abdominal pressure leads to an increase in the intracranial pressure and a decrease in the cerebral perfusion pressure. We studied the relationship between the IAP and the cerebral oxygenation with the use of the ne...

In this paper, we propose the application of time-domain near-infrared spectroscopy to the assessment of oscillations in cerebral hemodynamics. These oscillations were observed in the statistical moments of the distributions of time of flight of photons (DTOFs) measured on the head. We analyzed the zeroth and second centralized moments of DTOFs (to...

A novel technique for imaging of a small animal with application of time-gated intensified CCD camera was proposed. The time-resolved method based on emission of picosecond light pulses and detection of the light penetrating in tissues was applied. In this technique, the fluorescence photons, excited in the dye circulating in the tissue, that diffu...

The aim of the study was to assess causal coupling between neuronal activity, microvascular hemodynamics and blood supply oscillations in the Mayer wave frequency range. An electroencephalogram, cerebral blood oxygenation changes, an electrocardiogram and blood pressure were recorded during rest and during a movement task. Causal coupling between t...

An optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for the clinical assessment of brain perfusion at the bedside. We report on multiwavelength time-resolved diffuse reflectance spectroscopy measurements carried out on the head of a healthy adult during...

We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death. Different stages of cerebral perfusion disturbance were compared in three groups of subjects: controls, patients with posttraumatic cerebral...

Transcranial direct current stimulation (tDCS) is currently being used for research and treatment of some neurological and neuropsychiatric disorders, as well as for improvement of cognitive functions. In order to better understand cerebral response to the stimulation and to redefine protocols and dosage, its effects must be monitored. To this end,...

We propose a method to increase an amplitude of respiration-related wave in optical signal measured on a head. The method is based on cuff occlusion of abdominal part of the body of the subject.

Cerebral blood flow and hemoglobin concentration measured by diffuse correlation spectroscopy and time-resolved spectroscopy in patients with traumatic brain injury show different behaviour during hyperventilation therapy according to the functioning of the treatment.

Measurements of optical translucency of human skulls were carried out. An incandescent light source and a CCD camera were used to measure the distribution of light transmitted through the skull in 10 subjects post-mortem. We noticed that intra-individual differences in optical translucency may be up to 100 times but inter-individual translucency di...

We present an overview of the wide range of potential applications of optical methods for monitoring traumatic brain injury. The MEDLINE database was electronically searched with the following search terms: “traumatic brain injury,” “head injury,” or “head trauma,” and “optical methods,” “NIRS,” “near-infrared spectroscopy,” “cerebral oxygenation,”...

We have developed a high-resolution diffuse optical tomography system capable of carrying out measurements on an adult human head at source-detector separations 1.5-11.8cm. We present first results obtained during a Valsalva maneuver.

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...

Time-resolved near-infrared spectroscopy is a technique enabling the assessment of changes in oxygenation and perfusion of tissue with depth discrimination. A challenge in time-resolved measurements remains to provide sufficiently high efficiency of photons detection together with high temporal resolution of the setup. The aim of this study was to...

Dynamic mapping of the human brain by time-resolved near-infrared-spectroscopy (trNIRS), or functional NIRS (fNIRS), is based on the injection of picosecond or sub-nanosecond laser pulses into the head and the measurement of the pulse shape and the intensity after diffusion through the tissue. By analysing the pulse shape and the intensity of the s...

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 P...

The nEUROPt protocol is one of two new protocols developed within the European project nEUROPt to characterize the performances of time-domain systems for optical imaging of the brain. It was applied in joint measurement campaigns to compare the various instruments and to assess the impact of technical improvements. This protocol addresses the char...

A multi-center study has been set up to accurately characterize the optical properties of diffusive liquid phantoms based on Intralipid and India ink at near-infrared (NIR) wavelengths. Nine research laboratories from six countries adopting different measurement techniques, instrumental set-ups, and data analysis methods determined at their best th...

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.

The optical properties of the human head in the range from 600 nm to 1100 nm have been non-invasively investigated by various research groups using different diffuse optics techniques and data analysis methods.

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

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) estima...

We report on a fluorescence-based optical method for assessment of blood-brain barrier in humans. The technique is based on monitoring of fluorescence light excited in the dye circulating in the brain. Measurements were carried out in healthy volunteers and in patients with disruption of the blood-brain barrier with the use of time-resolved method...

Novel protocols were developed and applied in the European project "nEUROPt" to assess and compare the performance of instruments for time-domain optical brain imaging and of related methods of data analysis. The objective of the first protocol, "Basic Instrumental Performance", was to record relevant basic instrumental characteristics in a direct...

A time-gated intensified CCD camera was applied for time-resolved imaging of light penetrating in an optically turbid medium. Spatial distributions of light penetration probability in the plane perpendicular to the axes of the source and the detector were determined at different source positions. Furthermore, visiting probability profiles of diffus...

The near infrared spectroscopy may be implemented using various optoelectronic techniques, however, most of them do not allow to carry out measurements at short source-detector separation. We propose a method, based on time-gated intensified CCD camera, which allows for contactless measurements and can be carried out at short source-detector separa...

It was reported that time-resolved reflectance measurements carried out during inflow and washout of an optical contrast agent may provide information on the blood supply to the brain cortex of human adults. It was also shown that a measurement of fluorescence excited in the dye circulating in the brain is feasible. Unfortunately, patterns of time-...

Optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for clinical assessment of brain perfusion in adults at the bedside. Methodology of multiwavelength and time-resolved detection of fluorescence light excited in the ICG is presented and advantages of meas...

Time resolved measurements were carried out on the surface of the head during inflow of indocyanine green (ICG) in patients with severe brain perfusion disorders. Advantages of fluorescence light detection over diffuse reflectance was presented.

A novel protocol to determine sensitivity, spatial resolution and quantification of absorption changes in optical brain imaging was applied to assess time-domain instruments and methods of data analysis.

Intrinsic reduced scattering coefficient of Intralipid and intrinsic absorption coefficient of Indian ink at NIR wavelengths are accurately assessed in a multi-center study involving different techniques, instrumental set-ups, and analysis methods.

Recent studies have shown that time-resolved optical measurements of the head can estimate changes in the absorption coefficient with depth discrimination. Thus, changes in tissue oxygenation, which are specific to intracranial tissues, can be assessed using this advanced technique, and this method allows us to avoid the influence of changes to ext...

Recently, it was shown in measurements carried out on humans that time-resolved near-infrared reflectometry and fluorescence spectroscopy may allow for discrimination of information originating directly from the brain avoiding influence of contaminating signals related to the perfusion of extracerebral tissues. We report on continuation of these st...

In this paper we present methodological studies on construction and application of optical brain monitoring system utilizing time-resolved detection of fluorescence excited in the dye circulating in the human brain. Series of Monte Carlo simulations and time-resolved measurements of diffuse reflectance and fluorescence were carried out. Measurement...

An imaging system for brain oxygenation based on a time-gated, intensified charge-coupled device camera was developed. It allows one to image diffusely reflected light from an investigated medium at defined time windows delayed with respect to the laser pulse. Applying a fast optomechanical switch to deliver the light at a wavelength of 780 nm to n...

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...

A time resolved method based on near infrared spectroscopy for monitoring of changes in tissue absorption and concentration of the exogenoeus chromophore concentration is presented. We constructed a setup which can be used to measure changes in oxygenation of the brain tissue by monitoring of diffuse reflectance at two wavelengths. Currently, the i...

Time-resolved measurements of diffuse reflectance and fluorescence were carried out using phantom with dynamic inflow of indocyanine green (ICG) in tubes located at different depths. Better sensitivity of fluorescence signals related to the inflow of the dye was observed in comparison to simultaneously acquired diffuse reflectance. Obtained results...

Multi-wavelength detection of time-resolved fluorescence signal on the surface of the human head was carried out. Pattern of inflow and washout of indocyanine green in the head after intravenous injection of the dye was analyzed.

Time-resolved imager was used for monitoring of inflow of exogenous dye into the brain. We observed variation of fluorescence signals caused by changes of dose of the dye and position of optode on the head

A multi-laboratory study for the accurate calibration of diffusive liquid phantoms based on Intralipid and Indian ink has been performed. Different techniques, instrumental set-ups and analysis methods led to compatible values for optical properties.

Time−resolved measurements of diffuse reflectance and fluorescence were carried out using phantom with dynamic inflow of indocyanine green (ICG) in tubes located at different depths. Better sensitivity of fluorescence signals related to the inflow of the dye was observed in comparison to simultaneously acquired diffuse reflectance. Obtained results...

Monte Carlo simulations were applied for analysis of time-resolved fluorescence signals excited in dye distributed in two-layered tissue model mimicking human head. Obtained results allow for optimization of the time-resolved fluorescence detection setup.

We present results of application of a time-resolved optical system for imaging of fluorescence excited in an inclusion containing indocyanine green (ICG), and located in optically turbid medium. The developed imaging system enabled simultaneous acquisition of fluorescence and diffusive reflectance. Eight independent time-resolved measurement chann...

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...

Time-resolved optical imager allowing for recording of distributions of times of flight of photons for 32 source-detector pairs is presented. It was applied in in-vivo experiments during bolus of optical contrast agent.

We present construction of a multichannel time-resolved measurement system and results of its application in imaging of fluorescence excited in an inclusion filled with ICG and located in optically turbid medium.

A time-resolved optical instrument allowing for noninvasive assessment of cerebral oxygenation is presented. The instrument is equipped with picosecond diode lasers, fast photodetectors, and time-correlated single photon counting electronics. This technology enables depth-resolved estimation of changes in absorption and, in consequence, assessment...

The paper presents application of time-gated, intensified CCD camera for imaging of local changes of absorption in the non-homogenous liquid phantom. The surface of the phantom was illuminated sequentially at 25 points (forming 5×5 array) by laser beam at wavelength of 780 nm generated by picosecond, near-infrared diode laser. The spatial distribut...

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.

Time-resolved imaging system was constructed and experiments on a liquid physical phantom were carried out to show depth sensitivity of moments of measured distributions of times of flight of photons.

We present a multi-dimensional TCSPC technique that simultaneously records the photon distribution over the time in the fluorescence decay, the wavelength, and the coordinates of a two-dimensional scan or the time since the start of the experiment. We demonstrate the application of the technique to diffuse optical tomography, single-point autofluor...

Optical methods from the near infrared range, in particular the laser-Doppler flowmetry and the near infrared spectroscopy offer a new non-invasive, real-time technique for monitoring of the blood perfusion and oxygenation in a living tissue. In spite of some instrumental problems, e.g., relative calibration and unknown sampling measurement depth,...

Time-resolved optical measurements allow for evaluation of optical properties of the tissue (in particular, absorption and reduced scattering coefficient). A four-channel time-resolved spectroscopic system for measurements of the tissue optical properties is presented. Four semiconductor diode lasers were used for emission of picosecond pulses at w...

The laser Doppler method offers a non-invasive, real time technique for monitoring of blood perfusion in microcirculation. In practical measurements the perfusion index is given only in relative values. Thus, accurate and reproducible results can be only obtained when using a well controlled stimulation test. The aim of this study was evaluation of...

The aim of our study was to assess the occurrence of early functional abnormalities in the foot skin microcirculation in newly diagnosed type 1 diabetes patients. We have previously shown that the laser Doppler method is useful in identifying patients at high risk of diabetic foot complications. The study group comprised 50 patients: 26 newly diagn...

The purpose of this work was an improvement of the heart micropotential measurements and analysis by the simultaneous use of two non-invasive methods: body surface mapping and high-resolution electrocardiography. Software for body surface mapping and multi-lead high-resolution ECG analysis was developed. An analysis of the QRS duration and the ener...