Evaluation of D-dimer in postmortem blood using the SERATEC PMB Test

Biological material is a common type of evidence found at a crime scene, and body fluid identification is an essential process in crime scene investigation. One of the most common types of body fluids found is blood. After a stain has been presumptively identified as blood through the use of a colorimetric chemical test, additional testing may be necessary to better characterize the stain. SERATEC PMB Test is a relatively new lateral flow immunochromatographic assay that targets human hemoglobin and D-dimer simultaneously in order to distinguish peripheral blood and menstrual blood at the same time. Elevated levels of D-dimer, a fibrin degradation product, are found in menstrual blood, thrombosis formation and as part of the postmortem process. A previous study investigated levels of D-dimer in menstrual, peripheral and postmortem blood using the SERATEC PMB Test. In this study, all postmortem blood samples showed positive results for both hemoglobin and D-dimer; all peripheral bloodstain samples from living individuals showed positive results for hemoglobin detection, and negative results for D-dimer detection; and most menstrual bloodstain samples showed positive D-dimer results. The results suggest that this assay could be considered a presumptive test for both postmortem blood and menstrual blood. However, as D-dimer concentrations vary between individuals, additional testing is necessary to conclusively distinguish postmortem blood, menstrual blood and peripheral blood from living individuals with especially high D-dimer levels

Alignment of magnetic sensing and clinical magnetomyography

Neuromuscular diseases are a prevalent cause of prolonged and severe suffering for patients, and with the global population aging, it is increasingly becoming a pressing concern. To assess muscle activity in NMDs, clinicians and researchers typically use electromyography (EMG), which can be either non-invasive using surface EMG, or invasive through needle EMG. Surface EMG signals have a low spatial resolution, and while the needle EMG provides a higher resolution, it can be painful for the patients, with an additional risk of infection. The pain associated with the needle EMG can pose a risk for certain patient groups, such as children. For example, children with spinal muscular atrophy (type of NMD) require regular monitoring of treatment efficacy through needle EMG; however, due to the pain caused by the procedure, clinicians often rely on a clinical assessment rather than needle EMG. Magnetomyography (MMG), the magnetic counterpart of the EMG, measures muscle activity non-invasively using magnetic signals. With super-resolution capabilities, MMG has the potential to improve spatial resolution and, in the meantime, address the limitations of EMG. This article discusses the challenges in developing magnetic sensors for MMG, including sensor design and technology advancements that allow for more specific recordings, targeting of individual motor units, and reduction of magnetic noise. In addition, we cover the motor unit behavior and activation pattern, an overview of magnetic sensing technologies, and evaluations of wearable, non-invasive magnetic sensors for MMG

A compact dual-band implantable antenna for wireless biotelemetry in arteriovenous grafts

Arteriovenous grafts (AVGs) are indispensable life-saving implants for chronic kidney disease (CKD) patients undergoing hemodialysis. However, AVGs will often fail due to postoperative complications such as cellular accumulation termed restenosis, blood clots, and infections, which are dominant causes of morbidity and mortality. A new generation of hemodialysis implants equipped with biosensors and multi-band antennas for wireless power and telemetry systems that can detect specific pathological parameters and report AVGs’ patency would be transformative for CKD. Our study proposes a compact dual-band implantable antenna for hemodialysis monitoring applications. It operates in 1.4 GHz and 2.45 GHz for wireless power transfer and biotelemetry purposes. The miniaturized antenna with a current size of 5 × 5 × 0.635 mm 3 exhibits wide bandwidth (300 MHz at 1.4 GHz band and 380 MHz at 2.45 GHz band), along with good impedance matching at two resonance frequencies. In addition, simulations are performed separately in a three-layer homogenous phantom and a realistic human body model. Measurements of the proposed antenna are evaluated in minced pork. The measured results of the fabricated antenna prototype are closely harmonized with the simulation ones, and the effect of different proportions of fat tissue in pork mince was analyzed, to verify the sensitivity of the antenna to the contacting medium. The specific absorption rate (SAR) and link budget calculation are also analyzed. Finally, the wireless biotelemetry function of the proposed antenna is realized and visualized by adopting a pair of nRF24L01 wireless transceivers, and sustainable and stable wireless data transmission characteristics are shown at a high data rate of 2 Mbps with up to 20 cm transmission distance

MEMS magnetic field source for frequency conversion approaches for ME sensors

Some magnetoelectric sensors require predefined external magnetic fields to satisfy optimal operation depending on their resonance frequency. While coils commonly generate this external magnetic field, a microelectromechanical systems (MEMS) resonator integrated with permanent magnets could be a possible replacement. In this proof-of-concept study, the interaction of a MEMS resonator and the ME sensor is investigated and compared with the standard approach to achieve the best possible sensor operation in terms of sensitivity. The achievable sensor sensitivity was evaluated experimentally by generating the magnetic excitation signal by a coil or a small-sized MEMS resonator. Moreover, the possibility of using both approaches simultaneously was also analysed. The MEMS resonator operated with 20 Vpp at 1.377 kHz has achieved a sensor sensitivity of 221.21 mV/T. This sensitivity is comparable with the standard approach, where only a coil for sensor excitation is used. The enhanced sensitivity of 277.0 mV/T could be identified by generating the excitation signal simultaneously by a coil and the MEMS resonator in parallel. In conclusion, these MEMS resonator methods can potentially increase the sensitivity of the ME sensor even further. The unequal excitation frequency of the MEMS resonator and the resonance frequency of the ME sensor currently limit the performance. Furthermore, the MEMS resonator as a coil replacement also enables the complete sensor system to be scaled down. Therefore, optimizations to match both frequencies even better are under investigation

Investigating the Advantages of Magnetomyography in Assistive Healthcare Technology

Assistive healthcare technologies and prosthetics are crucial for individuals with muscle impairments. In 2005, the number of limb losses from trauma exceeded 700,000, projected to double by 2050, affecting approximately 1,326,000 civilians. Understanding the fundamental principles of muscle function, therefore, is key to developing innovative assistive technologies that can improve the quality of life for people with disabilities. Surface electromyography (sEMG), measuring electrical muscle activity, has long been a common tool in assistive technologies, but various obstacles have limited its widespread application. Capturing sEMG signals via the skin and subcutaneous fat poses a main challenge as they act as a low-pass filter and lead to the loss of critical information. Thus, new alternative technologies are needed to address this challenge. Magnetomyography (MMG) is a technology that can noninvasively measure magnetic muscle signals. Unlike sEMG, MMG signals are not affected by various tissues as they are transparent for magnetic signals. This paper presents the fundamental scenarios, including fat thickness on the EMG and MMG signals, with finite element (FE) simulations using COMSOL. The effects of 50-750 μ m fat on the recorded electrical and magnetic signals have been evaluated. The results indicate that by increasing fat thickness to 250μ m, the electrical signals decrease 66%, while MMG signals decline by 12%. Hence, the MMG can provide more accurate measurements of muscle activity for control strategies in prosthetic limbs

Wearable super-resolution muscle-machine interfacing

No abstract available

Investigating the Volume Conduction Effect in MMG and EMG during Action Potential Recording

The study and measurement of the magnetic field from the skeletal muscle is called Magnetomyography (MMG). These magnetic fields are produced by the same ion currents which give rise to the electrical signals that are recorded with electromyography (EMG). For non-invasive measurements, the electric properties of subcutaneous tissue, i.e., most importantly, have a strong influence on the recorded signals. This paper presents a computational model to study the volume conduction effect with the finite-difference time-domain simulations using Sim4Life. The effects of 1 mm fat on the recorded electrical and magnetic signals from the skin surface have been evaluated in both EMG and MMG. The results indicate that due to 1 mm fat, the electrical signals decrease over 60% through traveling across layers between the muscle and skin surface, while these layers are transparent to the magnetic field. In a similar simulation procedure, when the new fibers are recruited, the interference among electrical signals makes the strength of recorded signals behave non-linearly proportional to the increasing number of active muscle fibers. Sim4Life simulations show that the recorded magnetic signals do not have the same trajectory as electrical signals. Hence, the changes in EMG signals caused by volume conduction effect can result in signal misinterpretations

Study of Chopping Magnetic Flux Modulation on Surface Acoustic Wave Magnetic Sensor

Some methods of magnetic flux modulation are used to overcome flicker phase noise, low-frequency acoustical distortions, and movement artifacts. This work proposes employing a chopping flux modulation technique controlling a high permeability toroid together with a surface acoustic wave sensor inside. In this primary proof-of-concept study, an external magnetic field is generated to estimate quantitative signal parameters and the effect of the toroid shielding factor. Finally, the limitations of this approach should be identified and how low-frequency magnetic signals are influenced. The achievable sensitivity was empirically evaluated, and a quantitative signal quality value was calculated by estimating the signal power spectrum and noise power spectrum. Thus, the study compares the signal-plus-noise to noise ratio with and without magnetic flux modulation of a reproducible excitation magnetic signal generated by a solenoid coil. The experimental results show that the noise floor of this magnetic sensor system is improved. However, the signal-plus-noise to noise ratio without the modulation is 17 dB, and with the modulation, this parameter becomes 13 dB for a given mono-frequency signal of 20 μT . In perspective, this method exhibits disadvantages in reducing the sensitivity because, with the toroid inside, the calibration factor of the solenoid is not the same anymore, and the shielding factor reduces the field strength of the alternative-current field. Furthermore, the results show that the chopping flux modulation technique requires exploring how to compensate for the losses and setup issues that affect the magnetic field to define how suitable it is for surface acoustic waves magnetic sensors