Non-invasive Optical Measurement Research Articles

Determination of the Ion Concentrations in VRFB by Non-Invasive Optical Techniques Due to Chemical Reactions, Complexes, and Side Reactions

The Vanadium redox flow battery has been intensively examined since the 1970s, with researchers looking at its electrochemical time varying electrolyte concentration time variation (both tank and cells, for negative and positive half cells), its thermal time variation, and fluid flow behavior. Chemistry behavior of the electrolyte ions have also been intensively examined too. Our focus in this paper is to examine the disturbance and effect of other chemical reactions and constituents to those typically found in the positive electrode electrolyte, while handling the less problematic negative electrode. Appropriate formulas are developed which allow assessment of the size of the effect, and their evaluation indicates something on the order of up to 14%. Therefore, for unambiguous non-invasive optical measurements, knowledge of the disturbance effect, and taking it into account will allow proper concentration determination. This treatment includes a comprehensive examination of identified side reactions which occur due to crossover ions between the electrodes.

Shockwave velocimetry using wave-based image processing to measure anisotropic shock emission

Noninvasive optical measurements of the shockwave propagation velocity using multiple pulse illumination allow deducing the shockwave pressure amplitude through Hugoniot relations and an appropriate equation of state of the medium. This technique is particularly useful for spatially resolved measurements near the shockwave emission site. Due to diffraction, however, a shockwave front can significantly change its morphology, rendering precise velocity measurements non-trivial. As solution we propose a wave front evolution (WaFE) velocimetry technique, which applies Huygens principle. We take a shadowgraph of the wave front at subsequent times as initial condition for the acoustic Helmholtz equation and numerically propagate the fronts in time. From the instance of time, when two subsequently taken wave front shadows numerically interfere and form one sharp wave front, the local shock velocity is obtained and the local shock pressure amplitude measured. With artificial test images, it is shown that this technique has excellent sub-pixel accuracy, robustness to noise, and can work with low contrast images and even overlapping and interfering wave fronts. The software is made available freely and can be applied to general shock front velocity measurements. We apply WaFE to determine the anisotropic shockwave emission from an elongated laser-induced plasma in water from shadowgraphs of the shockwave front imaged four times onto the same camera frame using multiple pulse illumination at a repetition rate of 60 MHz. The direction dependence of attenuation of the shockwave pressure amplitude is measured at distances of 50–300 μm to the plasma.

Real-time temperature monitoring technology for dynamic combustion processes using dual-probe femtosecond CARS

We propose a fast responsive and non-invasive optical temperature measurement method which can be used to monitor the temperature of air-fed flames in real time. This method is based on femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (fs-CARS). Two probe pulses with different wavelengths are employed in the CARS system to generate two CARS signals, and the intensity ratio of the two CARS signals has a definite numerical relationship with temperature and therefore can be used to rapidly measure the flame temperature. The temperature of methane/air swirl flames was monitored by the dual-probe fs-CARS thermometry with a sampling rate of 100 Hz. For the steady swirl flame, the measured average temperature in the inner recirculation zone is 1551 K with a standard deviation of 3.7%. While, at a higher methane/air equivalent ratio of 0.74, the flame cannot remain steady, and the temperature frequently jumps from around 1700 K to 2000 K, causing the vortex to expand and break. A significant advantage of the dual-probe fs-CARS thermometry is that the temperature of the flame can be obtained immediately during the measurement without any post-processing. Therefore, this method is a potential candidate for accurately monitoring the real-time temperature of turbulent combustion.

Behaviour of Acoustically Levitated Drops in Mid-Water.

A low-impact acoustic levitation system has been developed to study immobilised single drops in liquid-liquid systems. The ability to observe liquid drops several millimetres in diameter for days enables fundamental research into a wide range of mechanisms. Non-invasive optical measurements with excellent optical accessibility are possible. This experimental work provides the basis for mass transfer studies, emphasizing the precise volume determination, signal noise, reproducibility, and the impact of the acoustic field on the drop and its surrounding environment. The setup can be effectively controlled and proves beneficial for research objectives provided that all liquid phases are entirely degassed, and there are no compressible voids present within the liquids. In addition to the precise, uniform, and reliable measurement conditions, we observed no acoustic streaming in the proximity of the drop and there was no significant vibration of the drop. Qualitative observations using rainbow schlieren deflectometry indicate that the nodal or anti-nodal planes of the standing waves can act as barriers to the dispersion of inhomogeneous dissolved substances in the continuous phase.

Microvascular Cerebral Blood Flow Monitoring Detects Response to Intrathecal Nicardipine Treatment for Vasospasm (S4.005)

<h3>Objective:</h3> Determining the effect of intrathecal nicardipine on microvascular cerebral blood flow <h3>Background:</h3> A common complication of subarachnoid hemorrhage is cerebral vasospasm, which is associated with delayed cerebral ischemia (DCI), a predictor of poor functional outcome. Intrathecal administration of nicardipine (ITn) upon detection of vasospasm holds promise as a treatment that reduces the incidence of secondary stroke. Herein, we utilize a novel non-invasive optical measurement of regional microvascular perfusion to determine the effect of ITn on microvascular cerebral blood flow (CBF). <h3>Design/Methods:</h3> In this observational study, we prospectively studied 20 patients with non-traumatic subarachnoid hemorrhage who were treated with ITn as part of usual care for evolving cerebral vasospasm. Regional microvascular CBF in the frontal cortex was measured with diffuse correlation spectroscopy for up to 90 min after the first treatment dose, and for a subset of patients, on days 2 and 3 of treatment as well. Outcome was assessed as the presence of DCI on imaging. <h3>Results:</h3> CBF increased significantly over the 90 min of monitoring after the first and subsequent doses (p&lt;0.001) in the absence of systemic hemodynamic changes. In general, the CBF response was heterogeneous across subjects. Using data from the first dose, a latent class mixture model was used to classify 19/20 patients into two distinct classes of cerebral blood flow response: patients in class 1 (n=6) showed a decrease or no change in CBF, while patients in class 2 (n=13) showed a pronounced increase in CBF in response to nicardipine. The incidence of DCI was 5/6 in class 1 and 0/13 in class 2 (p&lt;0.001). Similar significant differences in CBF response in patients with and without DCI were also observed on days 2 and 3 (both p&lt;0.001). <h3>Conclusions:</h3> Microvascular CBF monitoring is feasible in critically ill subarachnoid hemorrhage patients. CBF response may provide a valuable biomarker for treatment responsiveness. <b>Disclosure:</b> Dr. Sathialingam has nothing to disclose. Mr. Cowdrick has nothing to disclose. Ms. Urner has nothing to disclose. Ms. Liew has nothing to disclose. Dr. Sigman has nothing to disclose. Dr. Akbik has nothing to disclose. Dr. Samuels has received publishing royalties from a publication relating to health care. Dr. Kandiah has nothing to disclose. Dr. Buckley has received research support from Global Blood Therapeutics. Dr. Buckley has received research support from NIH. Ofer Sadan has received intellectual property interests from a discovery or technology relating to health care.

Dual-slope imaging of cerebral hemodynamics with frequency-domain near-infrared spectroscopy.

This work targets the contamination of optical signals by superficial hemodynamics, which is one of the chief hurdles in non-invasive optical measurements of the human brain. To identify optimal source-detector distances for dual-slope (DS) measurements in frequency-domain (FD) near-infrared spectroscopy (NIRS) and demonstrate preferential sensitivity of DS imaging to deeper tissue (brain) versus superficial tissue (scalp). Theoretical studies (in-silico) based on diffusion theory in two-layered and in homogeneous scattering media. In-vivo demonstrations of DS imaging of the human brain during visual stimulation and during systemic blood pressure oscillations. The mean distance (between the two source-detector distances needed for DS) is the key factor for depth sensitivity. In-vivo imaging of the human occipital lobe with FD NIRS and a mean distance of 31mm indicated: (1)greater hemodynamic response to visual stimulation from FD phase versus intensity, and from DS versus single-distance (SD); (2)hemodynamics from FD phase and DS mainly driven by blood flow, and hemodynamics from SD intensity mainly driven by blood volume. DS imaging with FD NIRS may suppress confounding contributions from superficial hemodynamics without relying on data at short source-detector distances. This capability can have significant implications for non-invasive optical measurements of the human brain.

528: CEREBRAL BLOOD FLOW MONITORING PREDICTS RESPONSE TO INTRATHECAL NICARDIPINE TREATMENT FOR VASOSPASM

Introduction: A common complication of subarachnoid hemorrhage is cerebral vasospasm, which is associated with delayed cerebral ischemia, a predictor of poor functional outcome. Intrathecal administration of nicardipine upon detection of vasospasm holds promise as a treatment that reduces the incidence of secondary stroke. Herein, we utilize a novel non-invasive optical measurement of regional microvascular perfusion to determine the effect of intrathecal nicardipine on microvascular cerebral blood flow (CBF). Methods: In this observational study, we prospectively studied 20 patients with non-traumatic subarachnoid hemorrhage who required an external ventricular drain to treat obstructive hydrocephalus and who were treated with intrathecal nicardipine as part of usual care for evolving cerebral vasospasm. Regional microvascular CBF in the frontal cortex was measured with diffuse correlation spectroscopy for up to 90 min after the first treatment dose, and for a subset of patients, on days 2 and 3 of treatment as well. Outcome was assessed as the presence of delayed cerebral ischemia on imaging. Results: CBF increased significantly over the 90 min of monitoring after the first dose (p< 0.001) in the absence of systemic hemodynamic changes. CBF also increased on average in response to repeated doses on days 2 and 3, although the magnitude of this response decreased with successive treatment day. In general, the CBF response was heterogeneous across subjects. Using data from the first dose, a latent class mixture model was used to classify 19/20 patients into two distinct classes of cerebral blood flow response: patients in class 1 (n=6) showed a decrease or no change in CBF, while patients in class 2 (n=13) showed a pronounced increase in CBF in response to nicardipine. The incidence of delayed cerebral ischemia was 5/6 in class 1 and 0/13 in class 2 (p< 0.001). Similar significant differences in CBF response in patients with and without delayed cerebral ischemia were also observed on days 2 and 3 (both p< 0.001). Conclusions: These results suggest that the CBF response to intrathecal nicardipine reaches a therapeutic steady state with successive treatment days. Moreover, the CBF response may provide a valuable biomarker for treatment responsiveness.

A Review of Research on the Vacuum Plume

Chemical and electrical thrusters are generally utilized to control the attitude and orbit of spacecraft in aerospace. When they are firing, the exhaust expands into the vacuum environment, known as the vacuum plume. The plume flow can collide with spacecraft surfaces due to sufficient expansion, exerting adverse effects on the spacecraft, such as heating load, force/torque, contamination, and sputtering. Therefore, it is vital to investigate the vacuum plume to ensure the function and safety of the spacecraft. This review introduces the ground test and numerical simulation methods of the vacuum plume for chemical and electrical thrusters. The vacuum environment, invasive, and non-invasive (optical) measurements of the ground test are concluded. Numerical simulation of plume flow and its effects is exampled. The hybrid CFD-DSMC (computational fluid dynamics and direct simulation Monte Carlo) algorithm is employed to simulate the gas plume flow spanning continuum and transitional and free molecular flow regimes for chemical thrusters. By contrast, the PIC-DSMC (particle-in-cell plus direct simulation Monte Carlo) algorithm is used for the plasma plume flow containing charged particles exhausted by electrical thrusters. Moreover, the topics of fast prediction of the vacuum plume, plume–surface interaction, and plume–Lunar/Mars regolith interaction are proposed for future research.

Abstract 303: Monitoring Tissue Oxygen Dynamics With A Novel Implantable Hydrogel Sensor In Patients With Pad

Objective: Tissue perfusion measurement remains a fundamental challenge in management of peripheral arterial disease (PAD) patients. Better measurement of baseline and dynamic changes after revascularization would aid clinical judgement. The Wireless Lumee® Oxygen System represents a novel approach to tracking tissue oxygen via a subcutaneous hydrogel that provides noninvasive optical oxygen measurements. This study’s objective was to assess the correlation of the Lumee sensor with transcutaneous oximetry (tcpO2) in PAD patients. Methods: The Lumee® Oxygen System is a subcutaneously placed hydrogel (0.5x0.5x5mm). Optical signals are captured with a skin surface reader sensing extravascular oxygenation. A pilot study assessed in vivo performance with inclusion criteria of peripheral arterial disease (Rutherford I-IV). Sensors were injected in the arm and foot and oxygenation measured before, during, and after proximal blood pressure cuff inflation (Figure) and Buerger’s Test modulation. The correlation (R) of oxygenation between tcpO2 and Lumee® was assessed following sensor placement at 2, 10, 90, 180, and 365 days. Results: Eleven subjects had 148 occlusion modulations over 199 days. Mean age was 67 years (range: 55-88), with 9% females, 45% White and 55% Black Race, Rutherford class I: 36%, II: 36%, III:27%. The median ABI was 0.83 (IQR0.69-1.14). In the arm, modulation was 56.9±24.6% (Lumee) and 84.7±9.2% (tcpO2), R:0.81. In the foot, modulation was 63.4±22.7% (Lumee) and 80.4±15.5% (tcpO2), R:0.79. No injection related adverse events occurred. Conclusion: Occlusion related changes in tissue oxygen can be detected by both tcpO2 and the Lumee sensor which strongly correlate in both the arm and foot. This pilot phase study supports expansion of the trial. The Lumee sensor shows promise for future evaluation of tissue oxygenation in PAD patients, which could be used to assess changes in tissue oxygenation over time and following revascularization.

Effect of Different Configurations on Bubble Cutting and Process Intensification in a Micro-Structured Jet Bubble Column Using Digital Image Analysis

An experimental study was conducted in this work to investigate the effect of different configurations on bubble cutting and process intensification in a micro-structured jet bubble column (MSJBC). Hydrodynamic parameters, including bubble size, flow field, liquid velocity, gas holdup as well as the interfacial area, were compared and researched for a MSJBC with and without mesh. The bubble dynamics and cutting images were recorded by a non-invasive optical measurement. An advanced particle image velocimetry technique (digital image analysis) was used to investigate the influence of different configurations on the surrounding flow field and liquid velocity. When there was a single mesh and two stages of mesh compared with no mesh, the experimental results showed that the bubble size decreased by 22.7% and 29.7%, the gas holdup increased by 5.7% and 9.7%, and the interfacial area increased by more than 34.8% and 43.5%, respectively. Significant changes in the flow field distribution caused by the intrusive effect of the mesh were observed, resulting in separate liquid circulation patterns near the wire mesh, which could alleviate the liquid back-mixing. The mass transfer experiment results on the chemical absorption of CO2 into NaOH enhanced by a mass transfer process show that the reaction time to equilibrium is greatly reduced in the presence of the mesh in the column.

Noninvasive Optical Measurements of Dynamic Cerebral Autoregulation by Inducing Oscillatory Cerebral Hemodynamics.

Objective: Cerebral autoregulation limits the variability of cerebral blood flow (CBF) in the presence of systemic arterial blood pressure (ABP) changes. Monitoring cerebral autoregulation is important in the Neurocritical Care Unit (NCCU) to assess cerebral health. Here, our goal is to identify optimal frequency-domain near-infrared spectroscopy (FD-NIRS) parameters and apply a hemodynamic model of coherent hemodynamics spectroscopy (CHS) to assess cerebral autoregulation in healthy adult subjects and NCCU patients.Methods: In five healthy subjects and three NCCU patients, ABP oscillations at a frequency around 0.065 Hz were induced by cyclic inflation-deflation of pneumatic thigh cuffs. Transfer function analysis based on wavelet transform was performed to measure dynamic relationships between ABP and oscillations in oxy- (O), deoxy- (D), and total- (T) hemoglobin concentrations measured with different FD-NIRS methods. In healthy subjects, we also obtained the dynamic CBF-ABP relationship by using FD-NIRS measurements and the CHS model. In healthy subjects, an interval of hypercapnia was performed to induce cerebral autoregulation impairment. In NCCU patients, the optical measurements of autoregulation were linked to individual clinical diagnoses.Results: In healthy subjects, hypercapnia leads to a more negative phase difference of both O and D oscillations vs. ABP oscillations, which are consistent across different FD-NIRS methods and are highly correlated with a more negative phase difference CBF vs. ABP. In the NCCU, a less negative phase difference of D vs. ABP was observed in one patient as compared to two others, indicating a better autoregulation in that patient.Conclusions: Non-invasive optical measurements of induced phase difference between D and ABP show the strongest sensitivity to cerebral autoregulation. The results from healthy subjects also show that the CHS model, in combination with FD-NIRS, can be applied to measure the CBF-ABP dynamics for a better direct measurement of cerebral autoregulation.

Acousto-Optical Volumetric Sensing of Acoustic Fields

The characterization of sound fields over space is fundamental in acoustics. Yet, the volumetric acquisition of sound fields using conventional electromechanical transducers is challenging due to the high sampling requirements needed in a three-dimensional domain. In this study, we introduce an acousto-optic sensing method to remotely sample acoustic fields in a volume using a sparse set of noninvasive optical measurements. Optical methods that use light as a sensing element have drawn significant attention recently, since they allow for remote, noninvasive sampling of acoustic fields with fine spatial resolution. The practical deployment of optical sensing in acoustics, however, has been hindered by the limited acquisition of data available, and the unsuitability of existing methods to reconstruct sound fields in scarce-data regimes. The proposed methodology relies on projecting the measured data on a basis that satisfies the wave equation, thus alleviating the measurement requirements associated with traditional reconstruction methods. The proposed approach leads to accuracy improvements of 20 dB relative to current methods, and a 90% reduction of measured data. We demonstrate the approach experimentally by reconstructing in situ the three-dimensional sound field inside a room from remote measurements of the acousto-optic interaction. These results are key to advancing the use of acousto-optical sensing methods, which are currently limited to simplified domains. The work presented in this paper brings about the possibility to solve so far intractable problems, such as the volumetric and remote acquisition of complex three-dimensional acoustic fields.

Optical Detection of Intracranial Pressure and Perfusion Changes in Neonates With Hydrocephalus

To demonstrate that a novel noninvasive index of intracranial pressure (ICP) derived from diffuse optics-based techniques is associated with intracranial hypertension. We compared noninvasive and invasive ICP measurements in infants with hydrocephalus. Infants born term and preterm were eligible for inclusion if clinically determined to require cerebrospinal fluid (CSF) diversion. Ventricular size was assessed preoperatively via ultrasound measurement of the fronto-occipital (FOR) and frontotemporal (FTHR) horn ratios. Invasive ICP was obtained at the time of surgical intervention with a manometer. Intracranial hypertension was defined as invasive ICP ≥15mmHg. Diffuse optical measurements of cerebral perfusion, oxygen extraction, and noninvasive ICP were performed preoperatively, intraoperatively, and postoperatively. Optical and ultrasound measures were compared with invasive ICP measurements, and their change in values after CSF diversion were obtained. We included 39 infants, 23 with intracranial hypertension. No group difference in ventricular size was found by FOR (P=.93) or FTHR (P=.76). Infants with intracranial hypertension had significantly higher noninvasive ICP (P=.02) and oxygen extraction fraction (OEF) (P=.01) compared with infants without intracranial hypertension. Increased cerebral blood flow (P=.005) and improved OEF (P<.001) after CSF diversion were observed only in infants with intracranial hypertension. Noninvasive diffuse optical measures (including a noninvasive ICP index) were associated withintracranial hypertension. The findings suggest that impaired perfusion from intracranial hypertension was independentof ventricular size. Hemodynamic evidence of the benefits of CSF diversion was seen in infants with intracranial hypertension. Noninvasive optical techniques hold promise for aiding the assessment of CSF diversion timing.

Does supply meet demand? A comparison of perfusion strategies on cerebral metabolism in a neonatal swine model

ObjectiveWe aimed to determine the effects of selective antegrade cerebral perfusion compared with other perfusion strategies on indices of cerebral blood flow, oxygenation, cellular stress, and mitochondrial function. MethodsOne-week-old piglets (n = 41) were assigned to 5 treatment groups. Thirty-eight were placed on cardiopulmonary bypass. Of these, 30 were cooled to 18°C and underwent deep hypothermic circulatory arrest (n = 10), underwent selective antegrade cerebral perfusion at 10 mL/kg/min (n = 10), or remained on continuous cardiopulmonary bypass (deep hypothermic cardiopulmonary bypass, n = 10) for 40 minutes. Other subjects remained on normothermic cardiopulmonary bypass (n = 8) or underwent sham surgery (n = 3). Novel, noninvasive optical measurements recorded cerebral blood flow, cerebral tissue oxyhemoglobin concentration, oxygen extraction fraction, total hemoglobin concentration, and cerebral metabolic rate of oxygen. Invasive measurements of cerebral microdialysis and cerebral blood flow were recorded. Cerebral mitochondrial respiration and reactive oxygen species generation were assessed after the piglets were killed. ResultsDuring hypothermia, deep hypothermic circulatory arrest piglets experienced increases in oxygen extraction fraction (P < .001), indicating inadequate matching of oxygen supply and demand. Deep hypothermic cardiopulmonary bypass had higher cerebral blood flow (P = .046), oxyhemoglobin concentration (P = .019), and total hemoglobin concentration (P = .070) than selective antegrade cerebral perfusion, indicating greater oxygen delivery. Deep hypothermic circulatory arrest demonstrated worse mitochondrial function (P < .05), increased reactive oxygen species generation (P < .01), and increased markers of cellular stress (P < .01). Reactive oxygen species generation was increased in deep hypothermic cardiopulmonary bypass compared with selective antegrade cerebral perfusion (P < .05), but without significant microdialysis evidence of cerebral cellular stress. ConclusionsSelective antegrade cerebral perfusion meets cerebral metabolic demand and mitigates cerebral mitochondrial reactive oxygen species generation. Excess oxygen delivery during deep hypothermia may have deleterious effects on cerebral mitochondria that may contribute to adverse neurologic outcomes. We describe noninvasive measurements that may help guide perfusion strategies.

Noninvasive optical measurement of microvascular cerebral hemodynamics and autoregulation in the neonatal ECMO patient.

BackgroundExtra-Corporeal Membrane Oxygenation (ECMO) is a life-saving intervention for severe respiratory and cardiac diseases. However, 50% of survivors have abnormal neurologic exams. Current ECMO management is guided by systemic metrics, which may poorly predict cerebral perfusion. Continuous optical monitoring of cerebral hemodynamics during ECMO holds potential to detect risk factors of brain injury such as impaired cerebrovascular autoregulation (CA).MethodsWe conducted daily measurements of microvascular cerebral blood flow (CBF), oxygen saturation, and total hemoglobin concentration using diffuse correlation spectroscopy (DCS) and frequency-domain diffuse optical spectroscopy in 9 neonates. We characterize CA utilizing the correlation coefficient (DCSx) between CBF and mean arterial blood pressure (MAP) during ECMO pump flow changes.ResultsAverage MAP and pump flow levels were weakly correlated with CBF and were not correlated with cerebral oxygen saturation. CA integrity varied between individuals and with time. Systemic measurements of MAP, pulse pressure, and left cardiac dysfunction were not predictive of impaired CA.ConclusionsOur pilot results suggest that systemic measures alone cannot distinguish impaired CA from intact CA during ECMO. Furthermore, optical neuromonitoring could help determine patient-specific ECMO pump flows for optimal CA integrity, thereby reducing risk of secondary brain injury.

Refractive index matching (RIM) using double-binary liquid\u2013liquid mixtures

For using microscopic multiphase flows in microreactors, an exact understanding of the underlying hydrodynamic interrelations is key for successful reactor layout and reaction control. To examine the local hydrodynamic behavior, non-invasive optical measurements techniques like particle tracking velocimetry (PTV) or micro particle image velocimetry (µPIV) are the methods of choice, since they provide precise velocity measurement with excellent spatial resolution. Such optical approaches require refractive index matching (RIM) of the involved flow phases to prevent optical distortion due to light refraction and reflection at the interfaces. Established RIM approaches often provide a single degree of freedom, which is sufficient to solely match the refractive index (RI) of the flow phases. Using these approaches, the material properties (Oh number) are fixed and the relevant dimensionless numbers (Ca, Re) may only be altered hydrodynamically or geometrically. To avoid expansive geometric scaling of the microchannels, we propose an approach using two binary mixtures (double-binary mixtures) to introduce an additional degree of freedom. The approach allows examining liquid–liquid two-phase flows at a distinct velocity while being able to change the material properties (Oh number). Thus, Ca and Re can be chosen individually and the proposed RIM-approach provides undisturbed optical access. Furthermore, we present four different binary mixtures, which allow to vary the viscosity ratio of the phases. The relevant material parameters are successfully correlated to measurement data, which delivers a system of equations that determines the mass fractions and the velocities to address Re and Ca individually. A proof-of-principle for the proposed double- binary mixture RIM-approach is successfully established using µPIV raw images.Graphic abstract

Non-invasive optical measurement of blood turbidity in capillary

Non-invasive optical measurement of blood turbidity in capillary

1 Assessing the energy status of porcine embryos by means of biodynamic imaging

Assisted reproductive technologies are powerful tools for enhancing production in livestock or treating infertility in humans. Unfortunately, the success rate of the technologies is rather low. A major reason for the poor efficiency is the lack of methods to reliably assess the developmental potential of the embryos before transfer into recipients. Therefore, a noninvasive method to ensure the selection of only the best embryos for transfer would be highly desirable. Biodynamic imaging is a compelling new microscopy that uses intracellular Doppler spectroscopy to perform label-free, noninvasive optical measurements of cellular fitness. The aim of this study was to investigate whether biodynamic imaging can be used to assess the energy status of the embryos, which may be indicative of their viability. Porcine oocytes matured invitro were parthenogenetically activated by an electrical pulse and cultured for 2 days. The parthenotes were then divided into two groups, and approximately half of them were incubated for an additional 2 days in the presence of 20mM sodium azide. Sodium azide is an inhibitor of oxidative phosphorylation and is known to block ATP production. The rest of the embryos were cultured without sodium azide and used as a control to indicate normal ATP levels. At the end of the culture period embryos that reached the 8- to 16-cell stage were evaluated by our biodynamic imaging system to assess their energy status, after which they were lysed and their ATP contents were determined by means of a bioluminescence assay. A total of 68 embryos (32 treated with the inhibitor and 36 control) were evaluated. The ATP content analysis showed that the control embryos had significantly more ATP than those treated with sodium azide as determined by Student's t-test (5.04±1.07 vs. 1.31±0.57; P&amp;lt;0.05). A correlative study was then completed where biodynamic biomarkers were used to classify embryos to estimate the ability of biodynamic imaging to identify embryos with high or low energy status. A set of 13 biomarkers representing each embryo as a feature vector was used to train a classifier. We found that the cross-validated classifier had a sensitivity and specificity of ~80%. In addition, a receiver-operator curve constructed by varying the ATP threshold of the independent bioluminescence assay had an area-under-the-curve of 0.81. These results indicate that biodynamic imaging is able to determine the energy status of the embryos noninvasively and has great potential in the assessment of embryo viability.

Changes of particle deposition caused by different breathing patterns during active lung simulation.

Aerosols are an integral part of everyday life and as such are inhaled under various conditions and circumstances. These may vary based on the health and activity status of an individual. The aim of this work is to analyse the particle deposition mechanisms during the simulation of three different breathing patterns using an aerosol representing the PM1 fraction of fine particles. The active electro-mechanical lung simulator xPULM is utilized as a driving force and is combined with a non-invasive direct reading optical aerosol measurement system. Results show differences between the number of deposited particles for the three breathing patterns and for the three typical size ranges of airborne particles. Overall, the presented approach demonstrates the possibility of determining the changes of aerosol uptake based on different breathing patterns using the electro-mechanical lung simulator and laboratory produced aerosols. Further measurement cycles must be performed in order to validate the found interactions and to characterize the major influencing parameters.

Non-Invasive Optical Blood Glucose Measurement based on Discrete Fourier Transform and Fast Artificial Neural Network: Fasting Normal Glucose Participants Case Study

A prototype non-invasive blood glucose level measurement optical device (NI-BGL-MOD) has been developed. The NI-BGL-MOD uses a discrete Fourier transform (DFT) method and a fast artificial neural network algorithm to optimize device performance. The appropriate light-emitting diode for the sensory module was selected based on near-infrared spectrophotometry of a blood glucose model and human blood. DFT is implemented in an analog-to-digital converter module. An in vitro trial using the blood glucose model along with a clinical trial involving 110 participants were conducted to evaluate the performance of the prototype. The root-mean-square error of the prototype was 10.8 mg/dl in the in vitro trial and 3.64 mg/dl in the clinical trial, which is lower than the ISO-15197:2016 mandated value of 10 mg/dl. In each trial, consensus error grid analysis indicated that the measurement error was within the safe range. The sensitivity and specificity of the prototype were 0.83 (0.36, 1.00) and 0.90 (0.55, 1.00) in the in vitro trial and 0.81 (0.75, 0.85) and 0.83 (0.78, 0.87) in the clinical trial, respectively. In general, the proposed NI-BGL-MOD demonstrated good performance than gold-standard measurement. Key words: Non-invasive blood glucose measurement, optical device, discrete Fourier transform, multi-formulatric regression, fast artificial neural network