Non-invasive Measurement Technique Research Articles

Non-Invasive Glucose Measurement Technique Based on Time-of-Flight

Non-Invasive Glucose Measurement Technique Based on Time-of-Flight

A novel approach for contactless heart rate monitoring from pet facial videos.

Monitoring the heart rate (HR) of pets is challenging when contact with a conscious pet is inconvenient, difficult, injurious, distressing, or dangerous for veterinarians or pet owners. However, few established, simple, and non-invasive techniques for HR measurement in pets exist. To address this gap, we propose a novel, contactless approach for HR monitoring in pet dogs and cats, utilizing facial videos and imaging photoplethysmography (iPPG). This method involves recording a video of the pet's face and extracting the iPPG signal from the video data, offering a simple, non-invasive, and stress-free alternative to conventional HR monitoring techniques. We validated the accuracy of the proposed method by comparing it to electrocardiogram (ECG) recordings in a controlled laboratory setting. Experimental results indicated that the average absolute errors between the reference ECG monitor and iPPG estimates were 2.94 beats per minute (BPM) for dogs and 3.33 BPM for cats under natural light, and 2.94 BPM for dogs and 2.33 BPM for cats under artificial light. These findings confirm the reliability and accuracy of our iPPG-based method for HR measurement in pets. This approach can be applied to resting animals for real-time monitoring of their health and welfare status, which is of significant interest to both veterinarians and families seeking to improve care for their pets.

Generalized super-resolution 4D Flow MRI - using ensemble learning to extend across the cardiovascular system.

4D Flow Magnetic Resonance Imaging (4D Flow MRI) is a non-invasive measurement technique capable of quantifying blood flow across the cardiovascular system. While practical use is limited by spatial resolution and image noise, incorporation of trained super-resolution (SR) networks has potential to enhance image quality post-scan. However, these efforts have predominantly been restricted to narrowly defined cardiovascular domains, with limited exploration of how SR performance extends across the cardiovascular system; a task aggravated by contrasting hemodynamic conditions apparent across the cardiovasculature. The aim of our study was therefore to explore the generalizability of SR 4D Flow MRI using a combination of existing super-resolution base models, novel heterogeneous training sets, and dedicated ensemble learning techniques; the latter-most being effectively used for improved domain adaption in other domains or modalities, however, with no previous exploration in the setting of 4D Flow MRI. With synthetic training data generated across three disparate domains (cardiac, aortic, cerebrovascular), varying convolutional base and ensemble learners were evaluated as a function of domain and architecture, quantifying performance on both in-silico and acquired in-vivo data from the same three domains. Results show that both bagging and stacking ensembling enhance SR performance across domains, accurately predicting high-resolution velocities from low-resolution input data in-silico. Likewise, optimized networks successfully recover native resolution velocities from downsampled in-vivo data, as well as show qualitative potential in generating denoised SR-images from clinicallevel input data. In conclusion, our work presents a viable approach for generalized SR 4D Flow MRI, with the novel use of ensemble learning in the setting of advanced fullfield flow imaging extending utility across various clinical areas of interest.

ESTIMATION OF VEHICLE YAW SPEED USING PHOTOGRAMMETRY OF TIRE TRACKS AT TRAFFIC ACCIDENT SCENES

Background: This article presents a study on the use of photogrammetry to determine the critical yaw radius of automotive vehicles and, consequently, estimate the skidding speed. Photogrammetry is a non-invasive measurement technique that uses images to digitally reconstruct three-dimensional objects and analyse their geometric characteristics. Aim: The study aims to capture and process images of tire tracks from a vehicle in skidding conditions at the scene of a traffic accident to calculate the critical yaw radius and determine the skid speed. Methods: Images were rectified using specialized software and then processed to calculate the critical yaw radius, allowing the skid speed to be determined based on specific mathematical models. Results: The results obtained demonstrate the predictions and accuracy of photogrammetry as an effective tool for vehicle safety analysis and vehicle dynamics studies in skidding conditions. Discussion: This approach not only provides important information for the development of stability control systems, but also contributes to a deeper understanding of the specificities related to vehicle safety in critical driving situations. Conclusions: Photogrammetry proves to be a valuable method in enhancing vehicle safety analysis and understanding vehicle dynamics during skidding incidents.

Potential of Near-Infrared Optical Techniques for Non-invasive Blood Glucose Measurement: A Pilot Study

BackgroundDiabetes mellitus manifested by escalated blood glucose, demands periodic or continuous glucose monitoring in the pursuit of improved control, optimal management, and appropriate medication. The existing state-of-the-art for blood glucose estimation are invasive methodologies necessitating the acquisition of blood sample through either a finger-stick or venipuncture. MethodsWe propose a dual Near-infrared wavelength integrated in a 3D printed enclosure as the optical prototype for non-invasive glucose estimation. We acquired data from both diabetic and healthy subjects with the developed system and subsequently validated the system. ResultsThe system demonstrated commendable clinical accuracy, as evidenced by the alignment of data pairs representing actual blood glucose levels and blood glucose levels predicted by our optical system within the A+B zones of the Parkes error grid and zones of no-risk and lower risk as defined by the surveillance error grid. We achieved compliant pairs percentage of 95.6%, which satisfies the accuracy requirements of the blood glucose monitoring surveillance study. The mean absolute percentage error attained with the proposed device (5.99%) was significant in predicting the blood glucose. ConclusionWe successfully deployed the NIR wavelengths functionality as the promising approach for glucose monitoring, offering new possibilities for improved medical interventions.

Contrast-Enhanced Ultrasound of Mouse Models of Hindlimb Ischemia Reveals Persistent Perfusion Deficits and Distinctive Muscle Perfusion Patterns

ObjectiveMouse models of hindlimb ischemia (HLI) are used to study peripheral arterial disease and evaluate novel therapies. Contrast-enhanced ultrasound (CEUS) is a noninvasive perfusion measurement technique that is increasingly being employed in these models. The objective of this study was to evaluate two models of severe HLI by CEUS to characterize perfusion recovery and muscle perfusion patterns. MethodsMice undergoing double femoral artery ligation were measured by CEUS and laser Doppler perfusion imaging (LDPI) at baseline and 1–150 d postsurgery. A second group undergoing femoral artery ligation and excision was measured 1–28 d postsurgery. ResultsBy LDPI, both surgeries showed robust perfusion recovery by 14 d postsurgery. However, by CEUS only a ∼40% perfusion recovery plateau was reached in either group. These results are consistent with our previous work, employing a less severe single femoral artery ligation, that showed perfusion in the ischemic limb does not return to normal by 150 d postsurgery. Cluster analysis of muscle perfusion patterns indicated 3–5 different patterns at day 1 postsurgery. The double ligation model yielded significantly less variable perfusion patterns, suggesting that it can provide more reproducible results. ConclusionContrary to LDPI, perfusion as measured by CEUS never fully recovers after hindlimb surgery, even when followed 28–150 d postsurgery. Individual mice can manifest different patterns of muscle perfusion to the same surgery, but these patterns are conserved within and between different surgical techniques. These results may have significant implications for the evaluation of novel therapeutics to treat PAD in mice.

A noninvasive measurement technique for the initial stiffness of the radial artery

Arterial stiffness carries significant implications for cardiovascular disease. Monitoring changes in arterial stiffness is integral to proactive health management, however, current noninvasive methods of quantifying stiffness in vivo rely primarily on linear tangent stiffness, making the measurements vulnerable to the variability of blood pressure and thereby affecting the accuracy in portraying the health status of the arteries. This study proposed a novel methodology for evaluating arterial stiffness that is unaffected by changes in blood pressure. Ultrasound detection techniques are applied to accurately chronicle changes in radial artery diameters across varied blood pressures. Incorporating blood pressure measurements, the initial diameter at cuff blockade, and vessel diameters at systolic and diastolic pressures enables inverse determination of the unstressed initial radial artery stiffness. This method accurately mirrors the results of in vitro experiments employing porcine blood vessels at physiological pressures. The results underscore the technique's ability to quantify arterial mechanical properties precisely. This study offers a groundbreaking strategy for fostering the early detection of atherosclerosis, and aiding artery health regulation.

Harnessing bioeffects of ultrasound triggered microbubble cavitation in medicine

The use of gas-filled microbubbles (1-10 mm in diameter) for ultrasound imaging is well established. Such contrast agents are used worldwide to improve the diagnostic capabilities of contrast enhanced ultrasound imaging (CEUS). At higher acoustic pressures (albeit well within United States Food and Drug Administration limits), the microbubbles undergo stable cavitation followed by destruction via gas diffusion and inertial cavitation, which produces numerous, localized bioeffects. Among these bioeffects, microbubble cavitation can improve drug delivery and sensitize solid tumors to radiation. This talk will discuss the variety of applications in which our laboratory investigates these bioeffects. Our pre-clinical and clinical trials to investigate the safety and therapeutic benefits of combining radioembolization and ultrasound-triggered microbubble destruction (UTMD) in patients with hepatocellular carcinoma (HCC) as well as the possibility of improving antibiotic treatment of joint infections with UTMD will be discussed. The current status of our ongoing trial of sonoporation in patients with pancreatic ductal adenocarcinoma (PDAC) will be presented. Moreover, we have developed a noninvasive pressure measurement technique, known as subharmonic-aided pressure estimation (SHAPE), which was used to acquire intra-tumoral pressure measurements. The use of SHAPE and other quantitative ultrasound techniques as biomarkers for predicting treatment response will also be presented.

Whole-Head Noninvasive Brain Signal Measurement System with High Temporal and Spatial Resolution Using Static Magnetic Field Bias to the Brain.

Noninvasive brain signal measurement techniques are crucial for understanding human brain function and brain-machine interface applications. Conventionally, noninvasive brain signal measurement techniques, such as electroencephalography, magnetoencephalography, functional magnetic resonance imaging, and near-infrared spectroscopy, have been developed. However, currently, there is no practical noninvasive technique to measure brain function with high temporal and spatial resolution using one instrument. We developed a novel noninvasive brain signal measurement technique with high temporal and spatial resolution by biasing a static magnetic field emitted from a coil on the head to the brain. In this study, we applied this technique to develop a groundbreaking system for noninvasive whole-head brain function measurement with high spatiotemporal resolution across the entire head. We validated this system by measuring movement-related brain signals evoked by a right index finger extension movement and demonstrated that the proposed system can measure the dynamic activity of brain regions involved in finger movement with high spatiotemporal accuracy over the whole brain.

Completely noninvasive multi-analyte monitoring system for cell culture processes

Although online monitoring of dissolved O2, pH, and dissolved CO2 is critical in bioprocesses, nearly all existing technologies require some level of direct contact with the cell culture environment, posing risks of contamination. This study addresses the need for an accurate, and completely noninvasive technique for simultaneous measurement of these analytes. A “non-contact” technique for simultaneous monitoring of dissolved O2, pH, and dissolved CO2 was developed. Instead of direct contact with the culture media, the measurements were made through permeable membranes via either a sampling port in the culture vessel wall or a flow cell. The efficacy of the “non-contact” technique was validated in Escherichia coli (E.coli), Chinese hamster ovary (CHO) culture processes, and dynamic environments created by sparging gases in cell culture medium. The measurements obtained through the developed techniques were comparable to those obtained through control methods. The noninvasive monitoring system can offer accurate, and contamination-minimized monitoring of critical process parameters including dissolved O2, pH, and dissolved CO2. These advancements will enhance the control and optimization of cell culture processes, promising improved cell culture performance.

Unbalanced Optimal Transport For Stochastic Particle Tracking

Non-invasive flow measurement techniques, such as particle tracking velocimetry, resolve 3D velocity fields by pairing tracer particle positions in successive time steps. These trajectories are crucial for evaluating physical quantities like vorticity, shear stress, pressure, and coherent structures. Traditional approaches deterministically reconstruct particle positions and extract particle tracks using tracking algorithms. However, reliable track estimation is challenging due to measurement noise caused by high particle density, particle image overlap, and falsely reconstructed 3D particle positions. To overcome this challenge, probabilistic approaches quantify the epistemic uncertainty in particle positions, typically using a Gaussian probability distribution. However, the standard deterministic tracking algorithms relying on nearest-neighbor search do not directly extend to the probabilistic setting. Moreover, such algorithms do not necessarily find globally consistent solutions robust to reconstruction errors. This paper aims to develop a globally consistent nearest-neighborhood algorithm that robustly extracts stochastic particle tracks from the reconstructed Gaussian particle distributions in all frames. Our tracking algorithm relies on the unbalanced optimal transport theory in the metric space of Gaussian measures. Specifically, we optimize a binary transport plan for efficiently moving the Gaussian distributions of reconstructed particle positions between time frames. We achieve this by computing the partial Wasserstein distance in the metric space of Gaussian measures. Our tracking algorithm is robust to position reconstruction errors since it automatically detects the number of particles that should be matched through hyperparameter optimization. Notably, our tracking algorithm also readily applies to the standard deterministic PTV case. Finally, we validate our method using an in vitro flow experiment using a 3D-printed cerebral aneurysm.

Contactless vital signs monitoring in macaques using a mm-wave FMCW radar

Heart rate (HR) and respiration rate (RR) play an important role in the study of complex behaviors and their physiological correlations in non-human primates (NHPs). However, collecting HR and RR information is often challenging, involving either invasive implants or tedious behavioral training, and there are currently few established simple and non-invasive techniques for HR and RR measurement in NHPs owing to their stress response or indocility. In this study, we employed a frequency-modulated continuous wave (FMCW) radar to design a novel contactless HR and RR monitoring system. The designed system can estimate HR and RR in real time by placing the FMCW radar on the cage and facing the chest of both awake and anesthetized macaques, the NHP investigated in this study. Experimental results show that the proposed method outperforms existing methods, with averaged absolute errors between the reference monitor and radar estimates of 0.77 beats per minute (bpm) and 1.29 respirations per minute (rpm) for HR and RR, respectively. In summary, we believe that the proposed non-invasive and contactless estimation method could be generalized as a HR and RR monitoring tool for NHPs. Furthermore, after modifying the radar signal-processing algorithms, it also shows promise for applications in other experimental animals for animal welfare, behavioral, neurological, and ethological research.

A comparative study of ProRithm and standard monitoring techniques for non-invasive blood pressure measurement using photoplethysmography and electrocardiography signals through artificial intelligence/machine learning methods

Background: Multi-parameter monitoring devices are essential for providing real-time patient data, which is crucial for effective healthcare interventions. This clinical trial evaluated the accuracy of the ProRithm beat-to-beat cuffless device for arterial blood pressure monitoring, comparing it with a standard sphygmomanometer. Methods: This observational study included 30 subjects aged 18 and above. Systolic and diastolic blood pressure measurements from both the ProRithm device and the Philips Monitor were compared using statistical analysis. Results: The analysis revealed no statistically significant differences between the ProRithm device and the manual method. In comparison with manual measurements using a sphygmomanometer, the mean systolic blood pressure was 131.2 mmHg with ProRithm it was 129.3 mmHg. Similarly, with the manual method, while the mean diastolic blood pressure was 76.2 mmHg and with ProRithm it was 75.9 mmHg. Conclusions: This study indicates that portable, small-sized devices like ProRithm, which facilitate remote monitoring, are effective for real-time blood pressure assessment in clinical settings.

Laser Doppler Vibrometer measurements of the 3D pressure field for the estimation of the radiation force produced by an acoustic standing-wave levitator

Acoustic levitation devices use powerful ultrasonic standing waves to levitate objects in mid-air. We have created a system and method to measure the full harmonic content of the acoustic field accurately. Our study revealed that levitated particles alter the pressure field in a way that is not immediately apparent from the first harmonic alone, highlighting the importance of precise and non-invasive measurement techniques. Our method uses computational tomography and optical sensing with the acousto-optic effect and a 3 DOF mechanical scanner. Our experiment results in a detailed 3D pressure distribution map for each harmonic of the ultrasonic acoustic field that generates the levitation forces.

Imaging diagnosis and treatment results of arteriovenous fistulas stenosis complication among hemodialysis patients

ABSTRACT Introduction: Percutaneous transluminal angioplasty (PTA) presents several advantages in addressing arteriovenous fistula (AVF) stenosis compared to surgical approaches. In addition, Doppler ultrasonography (DUS) serves as a noninvasive technique for stenosis measurement and access flow volume calculation. This study aimed to evaluate the agreement in stenosis diagnosis using PTA and DUS before intervention and to assess the effectiveness of the PTA method after intervention. Method: A non - controlled intervention study involved 15 chronic HD patients with a mature AVF in place for over three months, presenting AVF stenosis ≥ 50%, who underwent PTA intervention. Correlation analysis was employed to assess the similarity of AVF stenosis evaluations using DUS and PTA. The study also compared pre - and post - intervention indicators to evaluate the effectiveness of PTA intervention. Results: The results indicated a strong positive correlation between the two techniques (r = 0.997, r2 = 0.994, p < 0.001). Following intervention, all patients were considered successful, with significant reductions observed in various indicators, including alterations in murmurs along AVF, VAPR, the number of patients with AVF stenosis ≥ 50% on DUS, and none with Qmin < 500 mL/min. Conclusion: This study recommends utilizing DUS to evaluate stenosis before contemplating PTA intervention, owing to the correlation and similarity observed in the results of AVF stenosis examination between these two techniques. Ultimately, our research endorses PTA intervention as the preferred method for HD patients with AVF stenosis, considering the observed enhancements in clinical, hemodialysis, and DUS parameters

A neural network-based algorithm for the reconstruction and filtering of single particle trajectory in magnetic particle tracking.

Magnetic particle tracking (MPT) is a recently developed non-invasive measurement technique that has gained popularity for studying dense particulate or granular flows. This method involves tracking the trajectory of a magnetically labeled particle, the field of which is modeled as a dipole. The nature of this method allows it to be used in opaque environments, which can be highly beneficial for the measurement of dense particle dynamics. However, since the magnetic field of the particle used is weak, the signal-to-noise ratio is usually low. The noise from the measuring devices contaminates the reconstruction of the magnetic tracer's trajectory. A filter is then needed to reduce the noise in the final trajectory results. In this work, we present a neural network-based framework for MPT trajectory reconstruction and filtering, which yields accurate results and operates at very high speed. The reconstruction derived from this framework is compared to the state-of-the-art extended Kalman filter-based reconstruction.

An approach to solving the effect of background in fluidized bed on electromagnetic tomography

As a non-invasive measurement technique, electromagnetic tomography (EMT) system based on tunneling magneto resistance (TMR) can detect the distribution of medium in the gas–liquid–solid fluidized bed by the difference of permeability. The distribution of medium in the three-phase fluidized bed is not uniform, and the solid clusters and bubble clusters are formed in the background of the gas–liquid–solid mixture. Since the effect of the background in the pipe of the fluidized bed on the boundary measurement data of the TMR-EMT system is much greater, it is difficult to detect solid clusters and bubble clusters when the image is reconstructed directly using the boundary measurement data. In order to improve the detection of clusters by the TMR-EMT system, a method to weaken the effect of the background is proposed. The equivalent magnetic circuit model is used to estimate the background permeability. Then the magnetic dipole theory and demagnetization effect theory are utilized to establish a simple background compensation model based on the estimated background permeability. Using the compensation model, the effect of the background is weakened from the boundary measurement data and the cluster distribution information is highlighted. Simulation and experimental results demonstrate the effectiveness of the proposed method.

Acoustic response and ambient pressure sensitivity characterization of SonoVue for noninvasive pressure estimation.

Subharmonic aided pressure estimation (SHAPE) is a noninvasive pressure measurement technique based on the pressure dependent subharmonic signal from contrast microbubbles. Here, SonoVue microbubble with a sulfur hexafluoride (SF6) core, was investigated for use in SHAPE. The study uses excitations of 25-700 kPa peak negative pressure (PNP) and 3 MHz frequency over eight pressurization cycles between atmospheric pressure and overpressures, ranging from 0 to 25 kPa (0 to 186 mm Hg). The SonoVue subharmonic response was characterized into two types. Unlike other microbubbles, SonoVue showed significant subharmonic signals at low excitations (PNPs, 25-400 kPa), denoted here as type I subharmonic. It linearly decreased with increasing overpressure (-0.52 dB/kPa at 100 kPa PNP). However, over multiple pressurization-depressurization cycles, type I subharmonic changed; its value at atmospheric pressure decreased over multiple cycles, and at later cycles, it recorded an increase in amplitude with overpressure (highest, +13 dB at 50 kPa PNP and 10 kPa overpressure). The subharmonic at higher excitations (PNP > 400 kPa), denoted here as type II subharmonic, showed a consistent decrease with the ambient pressure increase with strongest sensitivity of -0.4 dB/kPa at 500 kPa PNP.

A non-invasive short range acoustic technique for liquid level measurement in containers

Techniques to measure liquid level in containers and vessels non-invasively are of great interest for the manufacturing, chemical industries, and energy sectors. Most commercial solutions use invasive techniques, which are not always practical and can lead to unsafe conditions when measuring devices encounter high pressures or hazardous chemical contents. In this study, a portable, non-invasive acoustic liquid level identification technique is developed. The technique relies on comprehensive analysis of acoustic guided wave modes in the container walls and their coupling to liquid contents to determine the optimal sensor separation distance and excitation signal characteristics, resulting in liquid level determination with high accuracy and precision. First, dispersion characteristics of guided wave propagation in container walls in contact with a liquid boundary are studied in detail. Based on the dispersion analysis a general-purpose short-range liquid level detection methodology is developed. The developed methodology is then validated using numerical wave propagation simulations and experiments on various metal containers with different physical characteristics, illustrating the versatility of the method. Compared to existing techniques, which are optimized for specific applications, the proposed method, due to its short range and non-invasive nature, has the potential for universal applicability on virtually any container, irrespective of its shape, size, wall-thickness, and whether it has any internal components.

Abstract TP139: Revascularization Improves Vascular Hemodynamics in Pediatric Moyamoya Patients

Introduction: Cerebrovascular reactivity (CVR) reflects the change in cerebral blood flow (CBF) in response to vasodilation. Studies have demonstrated that impaired CVR was associated with a higher risk of acute stroke in patients with intracranial vasculopathy and that bypass surgeries can reduce the risk of strokes. Moyamoya disease is a progress cerebrovascular disorder that begins during childhood. Arterial spin labeling (ASL) is a quantitative MRI technique for non-invasive CBF and CVR measurement; ASL with multiple delays can also measure arterial transit time (ATT). Here, we compare the CBF, CVR, and ATT in pediatric Moyamoya patients before and after bypass using multi-delay ASL. Hypothesis: CVR will increase significantly after bypass surgeries. Methods: Imaging data were acquired from 22 Moyamoya patients (11 months - 18 years, 14 females) using a 3T MRI system. All patients had unilateral or bilateral occlusion at ACA, MCA and/or PCA. Multi-delay ASL data (7 delays) were acquired at baseline and 15 minutes after acetazolamide administration. CBF and ATT were computed using the general kinetic model. CVR was computed as the percentage of CBF change compared with baseline CBF. Flow territories (right and left ACA, MCA, and PCA) were defined using the Harvard-Oxford atlases. Paired t-tests were conducted to compare the mean CVR, CBF, and ATT changes before and after bypass surgeries. Results: The figure shows the hemodynamic maps of an example patients. Overall, CVR and CBF in the affected regions increased after bypass; ATT in these regions decreased after bypass. For this cohort, our analysis showed that CVR of the affected regions increased significantly by 68% and ATT reduced significantly by 10.7% measured by multi-delay ASL, implying improved circulation and lower risk for strokes. Discussion: Multi-delay ASL was effective to detect improved CVR and reduced ATT in pediatric Moyamoya patients after bypass surgeries.