Closed-form equation to estimate the dielectric properties of biological tissues as a function of age.

Developing microwave systems for biomedical applications requires accurate dielectric properties of biological tissues for reliable modeling before prototyping and subject testing. Dielectric properties of tissues decrease with age due to the change in their water content, but there are no detailed age-dependent data, especially for young tissue-like newborns, in the literature. In this article, an age-dependent formula to predict the dielectric properties of biological tissues was derived. In the proposed method, the variation of water concentration in each type of tissue as a function of age was used to calculate its relative permittivity and conductivity. The derived formula shows that the concentration of water in each tissue type can be modeled as a negative exponential function of age. The dielectric properties of each tissue type can then be calculated as a function of the dielectric properties of water and dielectric properties of the organ forming the tissue and its water concentration. The derived formula was used to generate the dielectric properties of several types of human tissues at different ages using the dielectric properties of a human adult. Moreover, the formula was validated on pig tissues of different ages. A close agreement was achieved between the calculated and measured data with a maximum difference of only 2%. Bioelectromagnetics. 38:474-481, 2017. © 2017 Wiley Periodicals, Inc.

Dielectric properties of dog brain tissue measured in vitro across the 0.3-3 GHz band.

Dielectric properties of dead Greyhound female dogs' brain tissues at different ages were measured at room temperature across the frequency range of 0.3-3 GHz. Measurements were made on excised tissues, in vitro in the laboratory, to carry out dielectric tests on sample tissues. Each dataset for a brain tissue was parametrized using the Cole-Cole expression, and the relevant Cole-Cole parameters for four tissue types are provided. A comparison was made with the database available in literature for other animals and human brain tissue. Results of two types of tissues (white matter and skull) showed systematic variation in dielectric properties as a function of animal age, whereas no significant change related to age was noticed for other tissues. Results provide critical information regarding dielectric properties of animal tissues for a realistic animal head model that can be used to verify the validity and reliability of a microwave head scanner for animals prior to testing on live animals. Bioelectromagnetics. 37:549-556, 2016. © 2016 Wiley Periodicals, Inc.

Benign and Malignant Skin Lesions: Dielectric Characterization, Modelling and Analysis in Frequency Band 1 to 14 GHz.

OBJECTIVE: This paper aims to characterize Non-Melanoma malignancies and their corresponding benign conditions in ex-vivo/in-vivo tissue environments to study the feasibility of microwave techniques for skin cancer detection. METHODS: The dielectric dataset is developed across the frequency band 1 to 14 GHz using Keysight slim-form and RG405 probe characterization systems. The acquired reflection data captured by the systems is converted to dielectric values using the Open-Water-Short and Open-Water-Liquid calibration methods, respectively. Furthermore, the impact of anaesthesia application during skin excision procedure on ex-vivo dielectric data is investigated. RESULTS: The observations suggest that the dielectric properties (DPs) of excised skin lesions may not accurately represent actual tissue properties as they vary significantly (Dielectric Constant Contrast = 30.7%, Loss-Factor Contrast = 66.6%) compared to pre-excision conditions. In-vivo dielectric data analysis indicates that when compared to healthy skin, malignant Basal Cell Carcinoma presents increased DPs (dielectric constant & loss factor) of (24.8 & 38.6 %), respectively. On the other hand, for malignant Squamous Cell Carcinoma and pre-malignant Actinic Keratosis, the measured results show decreased DPs (dielectric constant & loss factor) accordingly by (19.4 & 18.2 %) and (19.2 & 27.9 %). The corresponding benign lesions have less than 13 % dielectric contrast compared to healthy skin across the tested band. CONCLUSION: The significant contrasts between in-vivo healthy and cancerous skin DPs strongly suggest the viability of the microwave band for skin cancer detection. SIGNIFICANCE: The research finding of this study would be critical in developing a portable electromagnetic system for skin cancer detection.

Combating Coronavirus Using Resonant Electromagnetic Irradiation.

The interaction of electromagnetic (EM) waves with the COVID-19 virus is studied to define the frequencies that cause maximum energy absorption by the virus and the power level needed to cause a lethal temperature rise. The full-wave EM simulator is used to model the virus and study the effects of its size and dielectric properties on the absorbed power across a wide range of frequencies. The results confirm potential resonance conditions, where specific frequencies produce maximum absorption and subsequent temperature rise that can destroy the virus. Furthermore, the study confirms that maximum power deposition in the virus occurs at specific wavelengths depending on its size. Also, the simulation is used to find the power required to destroy the virus and determine the total power required to destroy it in an oral activity, such as coughing, made by infected individuals. Furthermore, the study explained why irradiation by UV-C band is effective to decrease virus activity or even eradicate it.

Feasibility of Electromagnetic Knee Imaging Verified on Ex-Vivo Pig Knees.

OBJECTIVE: The potential of electromagnetic knee imaging system verified on ex-vivo pig knee joint as an essential step before clinical trials is demonstrated. The system, which includes an antenna array of eight printed biconical elements operating at the band 0.7-2.2 GHz, is portable and cost-effective. Importantly, it can provide daily monitoring and onsite real-time examinations imaging tool for knee injuries. METHODS: Six healthy hind legs from three dead adult pigs were removed at the hip and suspended in the developed system. For each pig, the right- and left-knee were scanning sequentially. Then ligament tear was emulated by injecting distilled water into the left knee joint of each pig for early (5 mL water) and mid-stage (10 mL water) injuries. The injured left knees were re-scanned. A modified multi-static fast delay, multiply and sum algorithm (MS-FDMAS) is used to reconstruct imaging of the knee. All knee's connective tissues, such as anterior and posterior cruciate ligaments (ACL, PCL), lateral and medial collateral ligaments (LCL, MCL), tendons, and meniscus, are extracted from a healthy hind leg along with collected synovial fluid. The extracted tissues and fluid were characterized and modelled as their data are not available in the literature, then imported to build an equivalent model for pig knee of 1 mm3 resolution in a realistic simulation environment. RESULTS: The obtained results proved potential of the proposed system to detect ligament/tendon tears. CONCLUSION: The proposed system has the potential to detect early knee injuries in a realistic environment. SIGNIFICANCE: Contactless EM knee imaging system verified on ex-vivo pig joints confirms its potential to reconstruct knee images. This work lays the groundwork for clinical EM system for detecting and monitoring knee injuries. (EM).

Implantable Sensor for Detecting Changes in the Loss Tangent of Cerebrospinal Fluid.

The increasing utilization of cerebrospinal fluid (CSF) in early detection of Alzheimer's disease (AD) is attributed to the change of Amyloid- ß proteins. Since, the brain is suspended in CSF, changes of Amyloid- ß proteins in CSF reflect a pathophysiological variation of the brain due to AD. However, the correlation between Amyloid- ß proteins and the dielectric properties (DPs) of CSF is still an open question. This paper reports the characterized DPs of CSF collected from canines using lumbar punctures. The CSF samples from canines show a strong correlation with respect to human in terms of the loss tangent, which indicates suitability of using canines as translational primates. Amyloid- ß [ Aß(1-40) and Aß(1-42)] proteins associated with AD were added to CSF samples in order to emulate AD condition. The results of emulated AD condition suggest a decrease in the relative permittivity and increase in the loss tangent. To detect changes in the loss tangent of CSF, which combines both relative permittivity and conductivity, a developed sensor is proposed. The designed sensor consists of a voltage controlled oscillator (VCO) and implantable antenna, which exhibits a wideband and low quality factor to be stable with respect to changes in the loss tangent of CSF. The measurements of the received power levels from the sensor in different liquid-based phantoms having different loss tangent values were used to correlate changes in the loss tangent. The developed correlation model is able to predict the loss tangent based on the received power level, which can be used to detect changes in the loss tangent of CSF due to AD. Consequently, this approach could be used as an early diagnosis of AD.

Millimeter-Wave Substrate Integrated Waveguide Probe for Skin Cancer Detection.

This article presents an efficient and low-cost near-field probe, designed for early-stage skin cancer detection. Thanks to a tapered section, the device can achieve a sharp concentration of electric field at its tip. Moreover, the adoption of substrate integrated waveguide (SIW) technology ensures an easy and cheap fabrication process. The probe is realized on a high dielectric constant substrate (Rogers RO3210) that provides a good impedance matching with the skin, thus allowing to use the device in direct contact with it. This feature is essential to ensure that the proposed system can be adopted as a practical and effective tool for a fast scanning of many suspected skin regions. The probe is designed to operate at around 40 GHz in order to achieve the penetration depth required to detect small cancer lumps in the skin, while preventing the fields from interacting with the underlying biological tissues. Furthermore, the concept of detection depth is defined with the goal of introducing a metric that is more suitable than the penetration depth to express the notion of the maximum distance from the skin surface at which a tumor can be detected. Thanks to a differential imaging algorithm, the probe is capable of working on every different skin types and body region. The proposed device has a lateral sensitivity and detection depth of 0.2 and 0.55 mm respectively. The probe was designed and tested through simulations in CST Microwave Studio, as well as fabricated and validated through measurements on an artificial human skin phantom.

Flexible Electromagnetic Cap for Head Imaging.

A wideband wearable electromagnetic (EM) head imaging system for brain stroke detection is presented. The proposed system aims at overcoming the challenges of size, rigidity, and complex structures of existing systems. The proposed system is built into a light-weight and compact imaging platform, which integrates a 16-element antenna array into a highly flexible custom-made wearable cap made of a cost-effective and robust room-temperature-vulcanizing (RTV) silicone. The system mitigates the mismatch between the skin and antenna array by introducing a flexible high-permittivity matching layer. The utilized compact antenna demonstrates wideband operational frequency over 0.6-2.5 GHz with a low signal distortion, safe values of SAR, and unidirectional radiations. The system is experimentally validated on realistic head phantoms. The polar sensitivity encoding (PSE) image processing algorithm is utilized to generate 2D images of different testing scenarios. The obtained images of a stroke-like target inside the head phantoms demonstrate the merits and feasibility of the system for preclinical trials.

Near-Field Inductive-Coupling Link to Power a Three-Dimensional Millimeter-Size Antenna for Brain Implantable Medical Devices.

OBJECTIVE: Near-field inductive-coupling link can establish a reliable power source to a batteryless implantable medical device based on Faraday's law of induction. METHODS: In this paper, the design, modeling, and experimental verification of an inductive-coupling link between an off-body loop antenna and a 0.9  three-dimensional (3-D) bowtie brain implantable antenna is presented. To ensure reliability of the design, the implantable antenna is embedded in the cerebral spinal fluid of a realistic human head model. Exposure, temperature, and propagation simulations of the near electromagnetic fields in a frequency-dispersive head model were carried out to comply with the IEEE safety standards. Concertedly, a fabrication process for the implantable antenna is proposed, which can be extended to devise and miniaturize different 3-D geometric shapes. RESULTS: The performance of the proposed inductive link was tested in a biological environment; in vitro measurements of the fabricated prototypes were carried in a pig's head and piglet. The measurements of the link gain demonstrated   in the pig's head and   in piglet. SIGNIFICANCE: The in vitro measurement results showed that the proposed 3-D implantable antenna is suitable for integration with a miniaturized batteryless brain implantable medical device (BIMD).