The automated classification of heart sounds plays a significant role in the diagnosis of cardiovascular diseases (CVDs). With the recent introduction of medical big data and artificial intelligence technology, there has been an increased focus on the development of deep learning approaches for heart sound classification. However, despite significant achievements in this field, there are still limitations due to insufficient data, inefficient training, and the unavailability of effective models. With the aim of improving the accuracy of heart sounds classification, an in-depth systematic review and an analysis of existing deep learning methods were performed in the present study, with an emphasis on the convolutional neural network (CNN) and recurrent neural network (RNN) methods developed over the last five years. This paper also discusses the challenges and expected future trends in the application of deep learning to heart sounds classification with the objective of providing an essential reference for further study.

https://www.mdpi.com/1099-4300/23/6/667/pdf

Deep Learning Methods for Heart Sounds Classification: A Systematic Review

The measurement of glucose concentration finds interesting potential applications in both industry and biomedical contexts. Among the proposed solutions, the use of microwave planar resonant sensors has led to remarkable scientific activity during the last years. These sensors rely on the changes in the dielectric properties of the medium due to variations in the glucose concentration. These devices show electrical responses dependent on the surrounding dielectric properties, and therefore the changes in their response can be related to variations in the glucose content. This work shows an up-to-date review of this sensing approach after more than one decade of research and development. The attempts involved are sorted by the sensing parameter, and the computation of a common relative sensitivity to glucose is proposed as general comparison tool. The manuscript also discusses the key points of each sensor category and the possible future lines and challenges of the sensing approach.

Microwave Planar Resonant Solutions for Glucose Concentration Sensing: A Systematic Review

Collaborative Drought Monitoring and Analysis: Examples from the NOAA National Centers for Environmental Information

Diabetes is a chronic and, according to the state of the art, an incurable disease. Therefore, to treat diabetes, regular blood glucose monitoring is crucial since it is mandatory to mitigate the risk and incidence of hyperglycemia and hypoglycemia. Nowadays, it is common to use blood glucose meters or continuous glucose monitoring via stinging the skin, which is classified as invasive monitoring. In recent decades, non-invasive monitoring has been regarded as a dominant research field. In this paper, electrochemical and electromagnetic non-invasive blood glucose monitoring approaches will be discussed. Thereby, scientific sensor systems are compared to commercial devices by validating the sensor principle and investigating their performance utilizing the Clarke error grid. Additionally, the opportunities to enhance the overall accuracy and stability of non-invasive glucose sensing and even predict blood glucose development to avoid hyperglycemia and hypoglycemia using post-processing and sensor fusion are presented. Overall, the scientific approaches show a comparable accuracy in the Clarke error grid to that of the commercial ones. However, they are in different stages of development and, therefore, need improvement regarding parameter optimization, temperature dependency, or testing with blood under real conditions. Moreover, the size of scientific sensing solutions must be further reduced for a wearable monitoring system.

/pdf/commercial-and-scientific-solutions-for-blood-glucose-2l33ztg2.pdf

Commercial and Scientific Solutions for Blood Glucose Monitoring—A Review

Biosensors have potentially revolutionized the biomedical field. Their portability, cost-effectiveness, and ease of operation have made the market for these biosensors to grow rapidly. Diabetes mellitus is the condition of having high glucose content in the body, and it has become one of the very common conditions that is leading to deaths worldwide. Although it still has no cure or prevention, if monitored and treated with appropriate medication, the complications can be hindered and mitigated. Glucose content in the body can be detected using various biological fluids, namely blood, sweat, urine, interstitial fluids, tears, breath, and saliva. In the past decade, there has been an influx of potential biosensor technologies for continuous glucose level estimation. This literature review provides a comprehensive update on the recent advances in the field of biofluid-based sensors for glucose level detection in terms of methods, methodology and materials used.

/pdf/recent-advancement-in-biofluid-based-glucose-sensors-using-2xfgcp8e.pdf

Recent Advancement in Biofluid-Based Glucose Sensors Using Invasive, Minimally Invasive, and Non-Invasive Technologies: A Review

Magnetic nanoparticles offer numerous promising biomedical applications, e. g. magnetic drug targeting. Here, magnetic drug carriers inside the human body are manipulated towards tumorous tissue by an external magnetic field. However, the success of the treatment depends strongly on the amount of drug carries, reaching the desired tumor region. This steering process is still an open research topic. In the proposed paper, an adjustable linear Halbach array to steer magnetic nanoparticles is investigated numerically using COMSOL Multiphysics. This Halbach array produces a relatively large region of a high magnetic field, while having a strong gradient. This results in a strong magnetic force, trapping many particles at the magnet. To avoid particle agglomeration, the Halbach array is rotated to its weak side. In this context, the force on the nanoparticles is evaluated for different magnet rotation angles. Comparing the weak and the strong magnetic side, the maximum and average magnetic force is a factor of 2.1 and 1.5 higher, respectively. Overall, the results depict the magnetic force and, thus, the region where the particles are able to get washed out, can be adjusted.

Steering Magnetic Nanoparticles by Utilizing an Adjustable Linear Halbach Array

The reliable localization for capsule endoscopes is an open research topic. In this study, a low-frequency magnetic localization method for capsule endoscopes with an integrated active coil is proposed. The spatial constraint, the limited battery capacity and the ferromagnetic battery shell of commercial capsules were considered. The generated magnetic flux density was evaluated depending on the distance to the coil and the maximal detectable range was determined. Twelve sensors were arranged in rings and by comparing the measured magnetic flux density with the analytic dipole model, the position and orientation of the coil were reconstructed. The results revealed that the ferromagnetic shell increases the magnetic moment of the coil by approximately a factor of 2.4. Moreover, the mean position and orientation errors were 0.5 mm and 0.3°. Furthermore, by using only the three closest sensors to the coil, a similar localization performance was achieved. Therefore, it was concluded that it is a feasible approach to choose the sensors, which measure the strongest signal to address the problem of the maximal detectable range of magnetic sensors. Moreover, by considering the limited battery capacity, the localization with the proposed coil must be conducted in short time intervals instead of continuously.

Quasi-Static Magnetic Localization of Capsule Endoscopes with an Active Integrated Coil

Abstract Magnetic Drug Targeting is a new approach in cancer therapy, where magnetic nanoparticles are used as carriers for cancer drugs. Commonly, external magnets are employed for steering the particles inside the blood vessels towards a desired direction. However, an unwanted side effect of the steering is the accumulation of the particles underneath the steering magnet. Many researchers address the number of accumulated particles, but, to the best of the authors’ knowledge, the retroaction of the accumulation profile on the generated magnetic field and, therefore, on the magnetic steering force, has not been investigated so far. Thus, in the proposed study, the influence of the accumulation profile on the magnetic force was numerically investigated. Therefore, a 2D model of a blood vessel with particles assumed as an accumulation profile and a nearby magnet was examined. Moreover, the length, thickness, and effective susceptibility of the approximated accumulation profile and the magnet size were varied. The results reveal that the field distribution is significantly affected, especially for high effective susceptibilities. The initially applied profile amplified the magnetic force; however, when the profile accumulated, it reduced the force up to 50 %. Overall, the results reveal that the retroaction of the particle distribution on the magnetic field must be considered in a simulation model.

Reduced Steering Performance in Magnetic Drug Targeting Induced by Shielding Arising from Accumulation of Particles

Magnetic Drug Targeting is a promising alternative for cancer treatment that offers the possibility to increase the efficiency of the therapy, while side-effects for patients get reduced. Thereby, the cancer-drug is bounded to magnetic nanoparticles. These particles are injected into a vessel and guided into the tumorous tissue by an external magnetic field outside the body. However, the efficiency of the therapy strongly depends on the performance of this navigation process, which is influenced by several multiphysical parameters including the properties of the nanoparticles, the volume flux, and especially the external applied magnetic field. To investigate these effects, the propagation of particle packets in a vessel with a 45° intersection is modeled in COMSOL Multiphysics®. The particles were distributed according to the density of a parabolic velocity profile. To systematically analyze the influence of the external magnetic field, the magnetic field of a cylindrical rare earth magnet with different ratios of diameter to length and axial plus radial magnetization was evaluated. The magnets were placed shortly before the intersection and for every magnet, the transmission probability for the two paths (direct and deflection) was evaluated. Furthermore, the probability for a particle gets trapped by the magnet and stop at the wall of the vessel, was investigated. The results for the particle steering show that both, the diameter to length ratio and the magnetization, strongly influence the steering of the particles. Overall, the magnets with an axial magnetization have a higher impact on the propagation path than the radial magnetized ones. However, when a single permanent magnet is used, the results depict that it is a narrow ridge between deflecting a particle or trap it at the vessel wall.

Investigation of Particle Steering for Different Cylindrical Permanent Magnets in Magnetic Drug Targeting

Static magnetic localization of capsule endoscopes is an established research area but the ferromagnetic battery shell of capsule endoscopes has not been investigated so far. Therefore, in this study, the batteries were enclosed by a ring magnet, suitable for a commercial capsule, and the magnetization effect of the ferromagnetic battery shell was evaluated. The magnet and the batteries were moved along the x-axis while the position and orientation errors were determined to investigate if the dipole model applies for the setup. The achieved mean position and orientation errors were below 1 mm and 0.1°, respectively. It was concluded that the built-in batteries can advantageously increase the magnetic flux density up to 25 %, depending on the magnetization direction of a ring magnet and the dipole model applies even with the enclosed batteries.

Angelika Thalmayer

Papers

Steering Magnetic Nanoparticles by Utilizing an Adjustable Linear Halbach Array

Quasi-Static Magnetic Localization of Capsule Endoscopes with an Active Integrated Coil

Reduced Steering Performance in Magnetic Drug Targeting Induced by Shielding Arising from Accumulation of Particles

Investigation of Particle Steering for Different Cylindrical Permanent Magnets in Magnetic Drug Targeting

Utilizing the Ferromagnetic Battery of Capsule Endoscopes for Static Magnetic Localization