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.

This paper proposes a robust and real-time capable algorithm for classification of the first and second heart sounds. The classification algorithm is based on the evaluation of the envelope curve of the phonocardiogram. For the evaluation, in contrast to other studies, measurements on 12 probands were conducted in different physiological conditions. Moreover, for each measurement the auscultation point, posture and physical stress were varied. The proposed envelope-based algorithm is tested with two different methods for envelope curve extraction: the Hilbert transform and the short-time Fourier transform. The performance of the classification of the first heart sounds is evaluated by using a reference electrocardiogram. Overall, by using the Hilbert transform, the algorithm has a better performance regarding the F₁-score and computational effort. The proposed algorithm achieves for the S₁ classification an F₁-score up to 95.7% and in average 90.5%. The algorithm is robust against the age, BMI, posture, heart rate and auscultation point (except measurements on the back) of the subjects.

Static magnetic localization is widely employed to localize capsule endoscopes. A permanent magnet is integrated into the capsule, and a sensor array outside the body measures its magnetic field. However, the geomagnetic flux density distorts the localization when no compensation method is applied. In this study, an optimized differential geomagnetic compensation method is proposed. A sensor array adapted to the typical abdomen size with 12 equally oriented sensors was used. The sensors are grouped into 26 pairs, and by subtracting the measured values of those, the geomagnetic field cancels out. This method was experimentally evaluated within a localization region of the size of a typical gastrointestinal tract. Static and dynamic scenarios in domestic environments were applied to evaluate the system in daily life situations. Moreover, the magnet was continuously moved while the traveled distance was recorded. The mean position and orientation errors for the static and dynamic scenarios did not exceed 4mm and 2°, respectively. Furthermore, the traveled distance of the magnet was tracked with an accuracy of 3.4 mm. Therefore, it was revealed that the proposed system is applicable in daily life scenarios and capable of precisely tracking the traveled distance of the capsule inside the intestine to locate abnormalities. Overall, the results significantly outperform state-of-the-art methods.

Magnetic localization is an excellent candidate for the localization of capsule endoscopes. A small magnet is embedded into the capsule, and its magnetic field is measured at a sensor array around the patient’s abdomen. However, relative movement between the abdomen and the array causes high localization errors. In this study, an innovative movement compensation method is proposed. A rigid array comprising 12 sensors was used to localize a permanent magnet. Furthermore, two orthogonal reference coils fed with a low-frequency signal were assumed to be fixed at the abdomen. The coils were alternately switched on and off, and thus, all three magnetic objects were separately localized since their magnetic fields can be distinguished in time and frequency domain. A reference coordinate system was set up with the coils, in which the magnet was localized. The proposed compensation method was evaluated for relative rotations and displacements between the sensors and the three magnetic objects. Moreover, the compensation method was evaluated for two reference magnets and compared with the coil-based approach. The mean position error was reduced by approximately a factor of ten from 41.5mm±15.5mm to 3.8mm±1.1 mm, respectively, and the orientation error did not exceed 3° for the coil-based compensation method. In contrast, with two reference magnets, the mean position and orientation errors were higher than 30mm and 20°, respectively. Consequently, it was shown that the coilbased method is the next step toward a wearable magnetic localization system to compensate for relative movement.

Traditional endoscopy is conducted stationary in the hospital and requires sedation of the patient. Contrary, capsule endoscopy requires no sedation and the patients are allowed to leave the hospital for their daily life during the procedure that lasts for several hours. Commercially available capsule endoscopes are passively moved through the gastrointestinal tract by peristalsis. For diagnosis and intervention planning, the traveled distance and orientation of the capsules for each video frame would be highly relevant. Nevertheless, commercial capsule endoscopes systems do not offer precise localization of the capsules. In the past years, many different scientific localization approaches have been proposed. These methods can be divided into video-, radio frequency- (RF), and magnetic field-based methods. In this review, a requirement profile for a localization method suitable for a commercial capsule endoscopy system is defined. These defined requirements of a localization system for capsule endoscopy are high accuracy, robustness during the daily life of a patient and integrability with commercial capsule endoscopy systems. Afterward, promising approaches are reviewed and discussed concerning these requirements. It was revealed that the magnetic field- and the video-based methods are the most promising methods and that these methods would complement each other very well. Therefore, a hybrid magnetic-field-/video-based method is suggested which has to the best of the authors’ knowledge not been proposed so far.

Magnetic nanoparticles offer numerous promising biomedical applications, e.g. magnetic drug targeting. Here, magnetic drug carriers inside the human body are directed towards tumorous tissue by an external magnetic field. However, the success of the treatment strongly depends on the amount of drug carriers, reaching the desired tumor region. This steering process is still an open research topic. In this paper, the previous study of a linear Halbach array is extended by an additional Halbach array with different magnetization angles between two adjacent magnets and investigated numerically using COMSOL Multiphysics. The Halbach arrays are arranged with permanent magnets and generate a relatively large region of a moderately homogeneous, high magnetic field while having a strong gradient. This results in a strong magnetic force, trapping many particles at the magnets. Afterwards, to avoid particle agglomeration, the Halbach array is flipped to its weak side. Therefore, the magnetic flux density, its gradient and the resulting magnetic force are computed for the different Halbach arrays with different constellations of magnetization directions. Since the calculation of the gradient can lead to high errors due to the used mesh in Comsol, the gradient was derived analytically by investigating two different fitting functions. Overall, the array with a 90^∘ shifted magnetization performs best, changing the magnetic sides of the array easily and deflecting more particles. Besides, the results revealed that the magnetic force dominates directly underneath the magnets compared to the other existing forces on the SPIONS. Summarized, the results depict that the magnetic force and, thus, the region where the particles are able to get washed out, can be adjusted using low-cost permanent magnets.