Novel image reconstruction algorithm for a UWB cylindrical microwave imaging system

A theoretical and experimental study of a novel image reconstruction algorithm for an Ultra Wide band (UWB) Microwave Imaging System aiming at detecting and locating small targets in a homogenous circular cylindrical dielectric body is presented. The system uses a double circular scan in which the second scan is achieved after rotating by a small angle the antenna sub-system or the imaged body. The obtained two sets of data serve the purpose of subtracting the background that masks the target. Assuming that the target is asymmetric with respect to the axis of rotation, the difference data includes the original target and its negative "ghost". In order to eliminate the "ghost" only the positive valued difference data is extracted. This data is scaled and mapped to show the original target location. The validity of the proposed image reconstruction algorithm is demonstrated in an example of a cylindrical plastic container filled with a vegetable oil and small cylindrical targets. © 2010 IEEE

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Microwave Imaging for Breast Cancer Detection

Breast cancer is the most common form of cancer found in women. Early detection and timely medical treatment are key factors affecting long-term survival of breast-cancer patients. XRay Mammography is currently the main method of screening for breast cancer. However exposure to ionizing radiation and high percentage of false negative and false positive diagnosis, expedite the need to develop a complementary or alternative screening method. This thesis proposes using Microwave Imaging as a viable alternative to X-ray mammography. Microwave imaging system is essentially a “breast tissue radar”. It involves the propagation of very low levels (1000 times less than a mobile phone) of microwave energy through the breast tissue to measure electrical properties. The reason for using microwave is the difference between the electrical properties of normal and malignant tissues in this frequency range. Normal breast tissue is largely transparent to microwave radiation while malignant tissues which contain more water and blood will scatter microwave back toward their source. The antenna array picks up these scattered signals, which can be analysed using a computer to construct a three dimensional image showing the malignant tissues’ location and size. An experimental study into a breast cancer detection technique employing a microwave imaging system is conducted. The system uses a step-frequency synthesized pulse technique and a planar or cylindrical near-field scanning sub-system to detect the presence of small objects inside a breast phantom. A simple breast phantom in the form of a cylindrical plastic container including liquid imitating fatty tissues and small highly reflecting objects approximately emulating tumours is used in the experimental set up. A special calibration technique for the Vector Network Analyser combined with a novel signal processing approach utilising frequency-domain data is employed to enhance detection of the target. Successful detection of the target is demonstrated. The work performed as part of this Ph.D. thesis has been published in 4 journal papers and 15 conference papers, all subjected to peer-reviewing. This acceptance rate supports the claim of the originality and significance of the research undertaken as part of the thesis project

Ultra wideband vias and power dividers in microstrip-slot technology

The design of ultra-wideband vias and power dividers in microstrip-slot technology is presented. The devices employ two substrates supported by a common ground plane. Their design is accomplished with the use of commercially available full EM analysis and design software. Low insertion loss and good return loss performances over an ultra wide frequency band for the designed structures are noted

A planar microwave imaging system with step-frequency synthesized pulse using different calibration methods

An experimental study of a planar microwave imaging system with step-frequency synthesized pulse for possible use in medical applications is described. Simple phantoms, consisting of a cylindrical plastic container with air or oil imitating fatty tissues and small highly reflective objects emulating tumors, are scanned with a probe antenna over a planar surface in the X-band. Different calibration schemes are considered for successful detection of these objects. (c) 2006 Wiley Periodicals, Inc

Compact reflectometers for a wideband microwave breast cancer detection system

The design of compact wideband microwave reflectometers for the purpose of inclusion in a breast cancer detection system is presented. In this system, a wideband frequency source is used to synthesize a narrow pulse via the step-frequency synthesis method. The reflectometer undertakes measurements in the frequency domain and the collected data is transformed into the time/space domain using IFFT. In order to accomplish reflection coefficient measurements over a large frequency band, compact wideband couplers and power dividers are used to form the reflectometer. Two compact six-port reflectometer configurations are investigated. One uses the Lange coupler and the Gysel power divider and the other one employs a 3dB slot-coupled microstrip coupler and a 2-stage Wilkinson power divider. The reflectometer employing the slot-coupled coupler and the Wilkinson divider provides a wider operational bandwidth, as shown by simulation results performed with Agilent AD

Investigations into breast cancer detection using ultra wide band microwave radar technique

An experimental investigation into capabilities of an Ultra Wideband (UWB) Microwave Radar to detect breast cancer is presented. A phantom, consisting of a cylindrical plastic container with a low dielectric constant material imitating fatty tissues and a high dielectric constant object emulating tumour, is scanned over a circular cylindrical surface with an UWB probe antenna. Following the collection of an experimental data, spatial images of the breast phantom are formed using two different approaches. One neglects and the other one compensates for the signal drop with distance. The approach compensating for the received signal drop enables a successful detection of tumour targets with a diameter as small as 5mm at different distances from the skin layer just by visual inspection of the produced image. ©2009 IEEE

UWB microwave imaging system including circular array antenna

The paper describes the design of an ultra wideband (UWB) microwave imaging system employing a 12-element circular array antenna. The array uses compact tapered slot antenna (TSA) elements operating over 3.1-10.6 GHz band. The elements of the array are activated by two coaxial SP6T switches that are connected to a vector network analyser (VNA) to achieve monostatic or multi-static radar modes of operation. In addition, the array is moved using a mechanical cylindrical scanning subsystem. This electronic/mechanical sub-system allows a fast highresolution scan of an imaged object. The paper describes the reasons for choosing this particular imaging system configuration and provides full construction details. Also shown are the imaging results of a circular plastic container filled with a vegetable oil and small diameter circular cylindrical targets using a novel image reconstruction algorithm

UWB cylindrical microwave imaging system with novel image reconstruction algorithm

Recent years have shown an increased interest in using active microwave techniques to obtain internal images of various objects. A particular focus has been on the application of these techniques to detect and locate a tumour within the woman's breast [1]. The detection principle is that the healthy and cancerous tissues have considerably different dielectric properties in the microwave frequency region. These differences can be observed from the microwave signals propagating across the breast tissues. One of the methods to detect and locate breast cancer, which has gained a lot of attraction recently, is based on an ultra wideband radar technique involving short duration pulses [1], [2]. The signals collected by UWB antennas are processed to locate regions producing an unusual backscatter within the image body. The detection of an unexpected large local backscatter inside the woman's breast, which is likely due to tumour, can be recommended for further diagnosis and eventual treatment. The technique requires an estimate of average dielectric properties of the woman's breast. Its main challenge comes from a large signal reflection at the air-body interface which masks a smaller magnitude return signal due to a cancerous tissue. In this paper, we apply an ultra wideband radar technique to detect and locate small cylindrical objects in a dielectric cylindrical body emulating the woman's breast. We propose a new image reconstruction algorithm which exploits the monopulse radar principle involving a 2-element array antenna. Using the difference of two signals received by the elements of this array, the part of the signal due to a background being symmetric with respect to the axis of the array is removed. The remaining part is the signal which is due to a scattering object located in the off-axis position of the array. The acquired set of difference signals obtained for various locations of the probing antenna is suitably scaled and mapped to show an internal image of the scanned body. The operation of this system including the new image reconstruction algorithm is demonstrated via full EM simulations and experiment. The paper is organised as follows. Section II describes the configuration and principles of operation of a UWB microwave imaging system including the image reconstruction algorithm. Section III describes simulation and experimental results. Section IV concludes the paper