B. Mohammed

Microwave System for Head Imaging

A wideband microwave system for head imaging is presented. The system includes an array of 16 corrugated tapered slot antennas that are installed on an adjustable platform. A switching device is used to enable the antennas to sequentially send a wideband 1-4 GHz microwave signal and capture the backscattered signals. Those signals are recorded using suitably designed virtual instrument software architecture. To test the capability of the system to detect brain injuries, a low-cost mixture of materials that emulate the frequency-dispersive electrical properties of the major brain tissues across the frequency band 1-4 GHz are used to construct a realistic-shape head phantom. A target that emulates a realistic hemorrhage stroke is fabricated and inserted in two different locations inside the fabricated head phantom. A preprocessing algorithm that utilizes the symmetry of the two halves of human head is used to extract the target response from the background reflections. A post-processing confocal algorithm is used to get an image of the phantom and to accurately detect the presence and location of the stroke.

Novel Preprocessing Techniques for Accurate Microwave Imaging of Human Brain

Two novel preprocessing techniques are applied to reinforce the detection performance and the image quality in microwave imaging systems designed for brain stroke detection. The image of energy distribution is obtained by applying a delay-and-sum beamforming to the backscattered signals measured using a hemielliptical array of 16 corrugated tapered slot antenna elements surrounding the head. The beamformer forms a spatially filtered combination of time-delayed response of scattering points in the head exposed to microwave radiation over the band from 1 to 4 GHz. The proposed techniques are validated on a realistic head phantom that is fabricated to emulate the electrical properties of real human head. The results show how the proposed techniques enable the detection and localization of hemorrhagic stroke accurately.

COMPACT WIDEBAND ANTENNA IMMERSSED IN OPTIMUM COUPLING LIQUID FOR MICROWAVE IMAGING OF BRAIN STROKE

This article reports on the design of a wideband compact microstrip-fed tapered slot antenna aimed at microwave imaging of a brain stroke. The antenna is immersed in a carefully designed coupling liquid that is used to facilitate higher signal penetration in the brain and thus increased dynamic range of the imaging system. A parametric analysis is used to find out the required properties of the coupling liquid. A suitable mixture of materials is then used to implement those properties. In order to protect the antenna from the adverse effects of the coupling medium, dielectric sheets are used to cover the radiator and the ground plane. To verify the proposed design in brain imaging, the antenna is tested using a suitable head model. It is shown that the antenna with a compact size (24 mm × 24 mm) on RT6010 substrate (dielectric constant = 10.2) operates efficiently over the band from 1 GHz to more than 4 GHz with more than 10 dB return loss. The time domain performance of the antenna supports its capability to transmit a distortion-less pulse with a high fidelity factor inside the head tissues.

Stroke detection based on variations in reflection coefficients of wideband antennas

In this paper, we investigate the possibility of using array of wideband antennas to differentiate between the two kinds of brain stroke: ischemic and hemorrhagic. Wideband antennas arranged as a circular array surrounding a human head and immersed in a coupling medium are used to monitor a suspected stroke area. The proposed method is based on comparing the reflection coefficients of any pair of antennas located symmetrically around the head. The simulated results indicate a promising method of using the variation in the reflection coefficient of the antennas to give a quick differentiation between different head strokes, which is a must for any possibility of a patient survival.

Circular antenna array for brain imaging systems

A brain imaging system that uses a circular array tapered slot wideband antennas is reported. The antenna utilized in the array is a corrugated microstrip-fed tapered slot antenna of compact dimensions (24 mm × 24 mm) immersed in a suitable coupling liquid for improved matching with the brain tissues. To protect the antenna elements from the harmful effects of the coupling liquid a dielectric sheets are used to cover the radiating elements. The proposed circular array includes ten wideband antenna elements that are designed to operate efficiently across the band from 1 GHz to 4 GHz. The developed array is tested using a phantom that emulates a stroke affected brain.

Ultra wideband antenna for portable brain stroke diagnostic system

Worldwide, stroke is the leading cause of adult disability. Stroke occurs when the blood supply in a part of brain is disturbed as a blood vessel bursts or is blocked by a clot. Delayed or wrong medical analysis can be fatal for the stroke affected patient. In this paper, a compact antenna is proposed for the brain stroke detection system. The antenna provides 77% fractional bandwidth (centered at 2 GHz) with stable gain and high front to back ratio. A compact radar-based system is developed using the proposed antenna for stroke detection. To test the system, a hemorrhagic stroke-affected human head is constructed emulating the actual electrical properties of human tissues. The image received by the post-processing algorithm explicitly detects and locates the position of the stroke.

Design of tapered slot antenna operating in coupling liquid for ultrawideband microwave imaging systems

This paper reports the design of a directive antenna for ultra-wideband microwave imaging systems. The antenna is a corrugated tapered slot antenna of compact dimensions (22 mm × 40 mm) immersed in a coupling liquid that is fabricated to improve the matching between the antenna and the imaged object, and thus to increase the dynamic range of the imaging system. The antenna is covered with a dielectric material in order to protect the radiating element from the adverse effects of the coupling liquid. The proposed antenna is designed to operate efficiently across the band from 3.1 GHz to 10.6 GHz. The designed antenna is tested in the presence of a breast phantom.The time domain response of the antenna indicates its capability to support distortionless pulse transmission with a high fidelity factor.

Planar array antenna for ultra wideband microwave imaging system

This paper reports the design of a planar antenna array for an ultra-wideband (UWB) microwave imaging system aimed for the operation in the band from 3.1 GHz to 10.6 GHz. The proposed planar array includes 6 × 2 UWB antenna elements in the form of compact (22 mm × 40 mm) corrugated tapered slot antennas (TSAs). The antenna elements are designed to operate in a coupling medium to improve the matching with the imaged object, and thus to increase the dynamic range of the imaging system. They are covered with a dielectric material to protect them from the adverse effects of the coupling liquid. The designed array is tested in the presence of a multilayer phantom representing an imaged object. The simulation performance of the designed array shows good impedance match and low mutual coupling of its elements and thus its readiness for use in UWB imaging system.

Wideband antenna for microwave imaging of brain

This paper reports the design of a wideband compact microstrip-fed tapered-slot antenna for brain imaging. The antenna is assumed to operate in a coupling liquid that is designed to improve the signal penetration of the imaged object, and thus to increase the dynamic range of the imaging system. The antenna is covered with a dielectric material in order to protect it from the harmful effects of the coupling liquid. The designed antenna operates across the band from 1 GHz to 4 GHz. Its performance is tested in the presence of a multilayer head phantom. The time domain response of the antenna indicates its capability to support distortionless pulse transmission with a high fidelity factor.

Detection and differentiation of brain strokes by comparing the reflection phases with wideband unidirectional antennas

A microwave frequency based differential technique is investigated to detect and differentiate between the two primary kinds of brain strokes namely ischemic and hemorrhagic strokes. A compact unidirectional antenna with wideband operation is designed to build a portable system for this purpose. This investigation is based on the fact that among the two identical halves of human brain, strokes usually occur in one part. An adult human head phantom is modeled with a stroke block in one side while the other half is healthy. Two antennas are placed in front of the two halves of human head. The reflection phases of the stroked head side antenna is collected and compared with those of normal side. From this comparison, the existence of stroked cells can be identified. Moreover, antennas facing the hemorrhagic strokes exhibits higher phase difference than those of ischemic strokes, which can be clearly noted from the best matched second resonance. This compact diagnostic system is validated with results received from various tests involving different stroke sizes and shapes.