Contactless passive diagnosis for brain intracranial applications: A study using dielectric matching materials

Abstract

A prototype system for passive intracranial monitoring using microwave radiometry is proposed. It comprises an ellipsoidal conductive wall cavity to achieve beamforming and focusing, in conjunction with sensitive multiband receivers for detection. The system has already shown the capability to provide temperature and/or conductivity variations in phantoms and biological tissue. In this article, a variant of the initially constructed modality is theoretically and experimentally investigated. Specifically, dielectric matching materials are used in an effort to improve the system's focusing attributes. The theoretical study investigates the effect of dielectric matching materials on the system's detection depth, whereas measurements with phantoms focus on the investigation of the system's detection level and spatial resolution. The combined results suggest that the dielectric matching layers lead to the improvement of the system's detection depth and temperature detection level. Also, the system's spatial resolution is explored at various experimental setups. Theoretical and experimental results conclude that with the appropriate combination of operation frequencies and dielectric layers, it is possible to monitor areas of interest inside human head models with a variety of detection depths and spatial resolutions.

Functional Brain Imaging Using Non-Invasive Non-Ionizing Methods: Towards Multimodal and Multiscale Imaging

“…Considering the above, as well as the wide variety of potentially harmful agents that coexist in contemporary everyday life, entirely passive, non-invasive and painless assessment of brain function in living subjects constitutes a wishful perspective and scientific vision. Under this rationale, the functional imaging perspective of a novel passive microwave imaging device is being investigated during the past 7 years (Karanasiou et al, 2004(Karanasiou et al, , 2008Karathanasis et al, 2010;Gouzouasis et al, 2010). Microwave radiometry is an important scientific research and application area of microwave sensing because it provides a passive sensing technique for detecting naturally emitted electromagnetic radiation.…”

“…Previous theoretical results have shown the system's ability to focus on specific areas of human head models with varying depths and positions with respect to the ellipsoidal focal point (Karanasiou et al, 2004;2008). Also, in an effort to improve the system's focusing properties several configurations using dielectric matching layers on the air -model interface or as filling material inside the ellipsoid chamber were tested both theoretically and experimentally showing promising results for the reduction of the scattering effects on the interface under consideration Gouzouasis et al, 2010). Both spatial resolution and detection depth provided by the system have been estimated through detailed theoretical analysis and validation experimental procedures using phantoms and animals (e.g.…”

“…Both spatial resolution and detection depth provided by the system have been estimated through detailed theoretical analysis and validation experimental procedures using phantoms and animals (e.g. Karanasiou et al, 2004Karanasiou et al, , 2008Karathanasis et al, 2010;Gouzouasis et al, 2010). In the range 1.3-3.5 GHz, imaging of the head model areas placed at the ellipsoid's focus is feasible with a variety of detection depths (ranging from 2 to 4.5 cm) and spatial resolution (ranging from less than 1 cm to over 3 cm), depending on the frequency used.…”

Theoretical Analysis of a Passive Acoustic Brain Monitoring System

“…At this point it should be noted that recently extensive theoretical and experimental work has been carried out by our research group in using microwave radiometry to develop a prototype imaging system (MiRaIS) [4][5][6][7]. The operating principle of the system is based on the use of an ellipsoidal conductive wall cavity for beamforming and focusing on the brain areas of interest.…”

“…One of the most important advantages of this method is that it operates in an entirely passive and non-invasive manner. MiRaIS has been used for the past 6 years in various experiments in order to evaluate its potential as an intracranial imaging device [4][5][6][7]. The MiRaIS system is able to provide real-time temperature and/or conductivity variation measurements in water phantoms and animals and potentially in subcutaneous biological tissues.…”