Passive microwave radiometry in biomedical studies

Passive microwave radiometry (MWR) measures natural emissions in the range 1–10 GHz from proteins, cells, organs and the whole human body. The intensity of intrinsic emission is determined by biochemical and biophysical processes. The nature of this process is still not very well known. Infrared thermography (IRT) can detect emission several microns deep (skin temperature), whereas MWR allows detection of thermal abnormalities down to several centimeters (internal or deep temperature). MWR is noninvasive and inexpensive. It requires neither fluorescent nor radioactive labels, nor ionizing or other radiation. MWR can be used in early drug discovery as well as preclinical and clinical studies

Electromagnetic metamaterials for biomedical applications: short review and trends

This mini-review examines the most prominent features and usages of metamaterials, such as metamaterial-based and metamaterial-inspired RF components used for biomedical applications. Emphasis is given to applications on sensing and imaging systems, wearable and implantable antennas for telemetry, and metamaterials used as flexible absorbers for protection against extreme electromagnetic (EM) radiation. A short discussion and trends on the metamaterial composition, implementation, and phantom preparation are presented. This review seeks to compile the state-of-the-art biomedical systems that utilize metamaterial concepts for enhancing their performance in some form or another. The goal is to highlight the diverse applications of metamaterials and demonstrate how different metamaterial techniques impact EM biomedical applications from RF to THz frequency range. Insights and open problems are discussed, illuminating the prototyping process

Measurement of Cerebral Circulation in Human

In this chapter, we review state-of-the-art non-invasive techniques to monitor and study cerebral circulation in humans. The measurement methods can be divided into two categories: direct and indirect methods. Direct methods are mostly based on using contrast agents delivered to blood circulation. Clinically used direct methods include single-photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI) with contrast agents, xenon computed tomography (CT), and arterial spin labeling (ASL) MRI. Indirect techniques are based on measuring physiological parameters reflecting cerebral perfusion. The most commonly used indirect methods are near-infrared spectroscopy (NIRS), transcranial Doppler ultrasound (TCD), and phase-contrast MRI. In recent years, few more techniques have been intensively developed, such as diffuse correlation spectroscopy (DCS) and microwave-based techniques, which are still emerging as methods for cerebral circulation monitoring. In addition, methods combining different modalities are discussed and, as a summary, the presented techniques and their benefits for cerebral circulation will be compared

Real-Time Passive Brain Monitoring System Using Near-Field Microwave Radiometry

Near-field microwave radiometry has emerged as a tool for real-time passive monitoring of local brain activation, possibly attributed to local changes in blood flow that correspond to temperature and/or conductivity changes. The aim of this study is to design and evaluate a prototype system based on microwave radiometry intended to detect local changes of temperature and conductivity in depth in brain tissues. A novel radiometric system that comprises a four port total power Dicke-switch sensitive receiver that operates at 1.5 GHz has been developed. Methods and Results: The efficacy of the system was assessed through simulation and experiment on brain tissue mimicking phantoms under different setup conditions, where temperature and conductivity changes were accurately detected. In order to validate the radiometer's capability to sense low power signals occurring spontaneously from regions in the human brain, the somatosensory cortices of one volunteer were measured under pain-inducing psychophysiological conditions. The promising results from the initial in vivo measurements prove the system's potential for more extensive investigative trials. Conclusion and Significance: The significance of this study lies on the development of a compact and sensitive radiometer for totally passive monitoring of local brain activation as a potential complementary tool for contributing to the research effort for investigating brain functionality. © 1964-2012 IEEE

Cerebral Circulation

Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system