Compact wideband folded strip monopole antenna for brain stroke detection

This paper introduces the CPW fed monopole antenna operating at multiple frequencies covering Ultra High Frequency (UHF) bands, suitable for biomedical applications. The planar antenna structure comprises an open loop and a dual folded monopole of optimized length. The antenna exhibits ultra-wideband frequency of operation ranges from 740 MHz to 4.02 GHz covering the frequency bands suitable for head imaging and heart failure detection. The proposed antenna has a compact size of 0.098λ × 0.079λ × 0.019λ where λ indicates wavelength corresponding to the lowest operating frequency. The antenna is further simulated on the human head model to corroborate applications for brain stroke detection. The specific absorption rate (SAR) value of the proposed antenna is compliant with SAR requirements set by IEEE standards. To experimentally verify the parameters of the proposed antenna design, the antenna is tested on the brain tissue model prepared by materials having dielectric properties like human brain tissue. The peak gain of the antenna, when tested on the human phantom, is 6.8 dBi.

Dielectric sensitivity of different antennas types for microwave-based head imaging: numerical study and experimental verification

The design of proper antenna element (AE) for microwave-based head imaging or brain stroke detection is a crucial challenge in the development process of microwave imaging (MWI) systems. The main purpose of this paper was to design, fabricate, and experimentally verify the compact and dimensions-reduced H-slot antenna suitable for the new generation of multichannel MWI system for brain stroke detection. The slot antenna type was chosen based on the numerical study of three AEs available in the literature, i.e. bow tie, slot, and waveguide-based. The study was focused on the sensitivity of the antennae (change of magnitude and phase of S21) due to dielectric parameters change or type and diameter of inclusion in a head phantom representing a hemorrhagic (HEM) or ischemic (ISCH) stroke phantom, respectively. Further, the analysis of antenna radiation to lossy medium/air and its immunity against plane wave exposure was carried out. The H-slot antenna was fabricated and experimentally verified (measurements of reflection as well as transmission coefficients) using a liquid head phantom with inserted HEM stroke phantom (both prepared as a mixture of propylene glycol, water, and salt). The phantoms were filled inside the designed two-port test system. Numerical models were validated by comparing calculated and measured S-parameters. The sensitivity of the H-slot antenna to the presence of the HEM stroke phenomenon within the phantom of the head was also demonstrated. The main advantage of the proposed H-slot antenna is its small dimensions, easy, inexpensive, and repeatable fabrication as well as mechanical stability.

Experimental Validation of Microwave Tomography with the DBIM-TwIST Algorithm for Brain Stroke Detection and Classification

We present an initial experimental validation of a microwave tomography (MWT) prototype for brain stroke detection and classification using the distorted Born iterative method, two-step iterative shrinkage thresholding (DBIM-TwIST) algorithm. The validation study consists of first preparing and characterizing gel phantoms which mimic the structure and the dielectric properties of a simplified brain model with a haemorrhagic or ischemic stroke target. Then, we measure the S-parameters of the phantoms in our experimental prototype and process the scattered signals from 0.5 to 2.5 GHz using the DBIM-TwIST algorithm to estimate the dielectric properties of the reconstruction domain. Our results demonstrate that we are able to detect the stroke target in scenarios where the initial guess of the inverse problem is only an approximation of the true experimental phantom. Moreover, the prototype can differentiate between haemorrhagic and ischemic strokes based on the estimation of their dielectric properties.