Detection of brain stroke in simulation and realistic 3-D human head phantom using microwave imaging

Brain stroke is globally one of the most widespread sorts of brain abnormalities. There are common symptoms between the transient ischemic attack (TIA), strokes and generic medical conditions like fainting, migraine, heart problems and seizures. Therefore, the other health conditions should not be misdiagnosed with stroke. It is well known that providing immediate medical attention for a patient with a brain injury is of vital importance. Every second, from the moment of brain injury, millions of brain cells die, leading to irreparable and permanent damage or even death. Thus, if medical staff diagnose stroke, and perform an appropriate drug treatment within a few hours of the symptoms onset, they play a crucial role in saving a patient’s life. The key factor in treatment is to reliably diagnose the stroke immediately. Hence, a portable diagnosic system is pivotal on the spot for rapid diagnosis of brain injuries. Initially, a clinical examination using a neurological assessment is performed by a general practitioner (GP). Compared to CT and MRI scanners, microwave imaging (MWI) can provide a portable detection system, and allow initial diagnosis of various emergency, life-threatening circumstances such as strokes due to brain injury, whilst patients are still being taken by ambulance to hospital, and saving critical time. In recent years, MWI has emerged as a promising non-ionising and non-invasive technology for a range of applications, particularly medical applications. In the current thesis, radar-based MWI is proposed as a procedure for brain haemorrhagic stroke detection. This imaging procedure has also more advantages such as low cost, being portable, fast, and easy to use with a good potential for brain haemorrhage detection. In MWI, the imaging of different human head tissues relies on their different response (i.e., electric contrast) to an applied microwave radiation. MWI is a screening technology for detection and monitoring of haemorrhagic stroke, tumours and cancerous cells, based on the significant contrast in the dielectric properties at microwave frequencies of normal and abnormal tissues. This thesis deals with the use and validation of an innovative low complexity MWI procedure for brain imaging, where antennas operate in free space. In particular, we employ only two microstrip antennas, operating between 1 and 2 GHz for successful detection of the haemorrhagic stroke. Detection is achieved using both simulation and experimental measurements. I. In the first stage, a wideband (WB) microstrip antenna with fractal ground plane is proposed, simulated and fabricated for brain haemorrhage detection. The designed antennas exhibit a WB working frequency between 1-2 GHz. This band has demonstrated to be ideal and optimal to do brain imaging; in addition, it is obviously emphasised that WB can enhance performance in lesion detection. The simulations have been performed applying an anthropomorphic human head model where a haemorrhagic stroke has been inserted (using CST Microwave studio). The simulation results concluded that the emulated brain haemorrhagic stroke can be distinguished at four different positions of 0◦, 5◦, 40◦, and 45◦. II. The second stage of this study presents a hemi-ellipsoidal human head phantom with a millimetric cylindrically-shaped inclusion to emulate brain haemorrhage (suitable to be used inside the anechoic chamber) and a human head phantom (suitable to be applied in MWI device). The process has been performed based on the following procedures: - In the second, stage, first, multi-biostatic frequency-domain measurements have been performed to collect the transfer function (S21) between two proposed mono-static radar system based antennas inside an anechoic chamber using a multi-layered phantom mimicking a human head. This procedure is used to measure the received signal (S21). A Vector Network Analyser (VNA) is linked to the mentioned antennas, and the measured (S21) are recorded when they changed the position to every new observation position. Subsequently, the measured (S21) are post-processed in order to generate microwave images with emphasising the object (e.g. the tumour or the stroke). In this stage, on the basis of the measurement results, it is concluded that the object (brain haemorrhagic stroke phantom) can be successfully detected at four different positions of 0◦, 90◦, 180◦ and 270◦. - Secondly, since the results coming from measurements inside the anechoic chamber are not as realistic as clinical trials reports and also there is a medical requirement for a brain stroke portable imaging device, we have come to a decision on applying different signal pre-processing methods to the imaging results collected from a portable MWI device for brain haemorrhage imaging. A portable MWI device, which operates in free space with two azimuthally-rotating antennas, has been used for brain haemorrhage detection. Measurements are performed by recording the complex (S21) in a multi-bistatic fashion, i.e. for each transmitting position the receiving antenna is moved to measure the received signal every 4.5◦, leading to a total of 80 receiving points. In conclusion, based on the results of the MWI device, the inclusion emulating the brain haemorrhage may be detected at four different positions of 0◦, 90◦, 180◦ and 270◦. In this thesis, all images have been obtained through Huygens Principle (HP). To reconstruct the image, signal pre-processing techniques are used to reduce artefacts (which may be due to the direct fields and the fields reflected by the first layer). Subtraction artefact removal method between the data of a healthy head and the data of a head with stroke has been initially employed in simulation and measurements. Accordingly, an "Ideal" image would be generated using this artefact removal method to prove the concept of the technology. This would mean that the "Ideal" image performed as a reference for the comparison with the resulting image from using other artefact removal methods. It is important to point out that, for the purposes of real scenario, there is no possibility of applying this artefact removal method to medical imaging, where the ideal response is not calculated or known. Hence, in clinical trials this artefact removal method cannot be helpful. In addition to the subtraction artefact removal method, in this research, four more methods have been introduced and investigated. These methods consist of rotation subtraction, average subtraction, differential symmetric receiver type, and summed symmetric differential. The subtraction and rotation subtraction artefact removal methods have been used both in simulations and measurements. It has been verified that all artefact removal procedures allow detection. Subsequently, 6 dedicated image quantification procedures have been implemented in order to assess the detection capability. These procedures comprise area difference, centroid difference, signal-to-noise ratio, structural similarity index metric, image quality index, and signal-to-clutter ratio. Validation of the techniques through both simulation and experimental measurements have been performed and presented, illustrating the effectiveness of the methods

UWB Microwave Imaging for Inclusions Detection: Methodology for Comparing Artefact Removal Algorithms

An investigation is presented on Artefact Removal Methods for Ultra-Wideband (UWB) Microwave Imaging. Simulations have been done representing UWB signals transmitted onto a cylindrical head-mimicking phantom containing an inclusion having dielectric properties imitating an haemorrhagic stroke. The ideal image is constructed by applying a Huygens’ Principle based imaging algorithm to the difference between the electric field outside the cylinder with an inclusion and the electric field outside the same cylinder with no inclusion. Eight different artefact removal methods are then applied, with the inclusion positioned at \u1d70b and −\u1d70b/4 radians, respectively. The ideal image is then used as a reference image to compare the artefact removal methods employing a novel Image Quality Index, calculated using a weighted combination of image quality metrics. The Summed Symmetric Differential method performed very well in our simulations

Free space operating microwave imaging device for bone lesion detection: a phantom investigation

In this letter, a phantom validation of a low complexity microwave imaging device operating in free space in the 1-6.5 GHz frequency band is presented. The device, initially constructed for breast cancer detection, measures the scattered signals in a multi-bistatic fashion and employs an imaging procedure based on Huygens principle. Detection has been achieved in both bone fracture lesion and bone marrow lesion scenarios using the superimposition of five doublet transmitting positions, after applying the rotation subtraction artefact removal method. A resolution of 5 mm and a signal to clutter ratio (3.35 in linear scale) are achieved confirming the advantage of employing multiple transmitting positions on increased detection capability

Developing Artefact Removal Algorithms to Process Data from a Microwave Imaging Device for Haemorrhagic Stroke Detection

In this paper, we present an investigation of different artefact removal methods for ultra-wideband Microwave Imaging (MWI) to evaluate and quantify current methods in a real environment through measurements using an MWI device. The MWI device measures the scattered signals in a multi-bistatic fashion and employs an imaging procedure based on Huygens principle. A simple two-layered phantom mimicking human head tissue is realised, applying a cylindrically shaped inclusion to emulate brain haemorrhage. Detection has been successfully achieved using the superimposition of five transmitter triplet positions, after applying different artefact removal methods, with the inclusion positioned at 0°, 90°, 180°, and 270°. The different artifact removal methods have been proposed for comparison to improve the stroke detection process. To provide a valid comparison between these methods, image quantification metrics are presented. An “ideal/reference” image is used to compare the artefact removal methods. Moreover, the quantification of artefact removal procedures through measurements using MWI device is performed

The road to developing economically feasible plans for green, comfortable and energy efficient buildings

Owing to the current challenges in energy and environmental crises, improving buildings, as one of the biggest concerns and contributors to these issues, is increasingly receiving attention from the world. Due to a variety of choices and situations for improving buildings, it is important to review the building performance optimization studies to find the proper solution. In this paper, these studies are reviewed by analyzing all the different key parameters involved in the optimization process, including the considered decision variables, objective functions, constraints, and case studies, along with the software programs and optimization algorithms employed. As the core literature, 44 investigations recently published are considered and compared. The current investigation provides sufficient information for all the experts in the building sector, such as architects and mechanical engineers. It is noticed that EnergyPlus and MATLAB have been employed more than other software for building simulation and optimization, respectively. In addition, among the nine different aspects that have been optimized in the literature, energy consumption, thermal comfort, and economic benefits are the first, second, and third most optimized, having shares of 38.6%, 22.7%, and 17%, respectively

Microwave imaging for stroke detection: validation on head-mimicking phantom

This paper provides initial results on the efficacy of Huygens Principle (HP) microwave imaging for haemorrhagic stroke detection. This is done using both simulations and measurements in an anechoic chamber. Microstrip antennas operating between 1 and 2 GHz have been designed, constructed and used for imaging a human head model in Computer Simulation Technology (CST) software. A 3D model consisting of human head tissues of Ella is employed in the simulation. An emulated haemorrhagic stroke with the dielectric properties equivalent to the blood has been inserted in Ella. Moreover, a 3-layered head-mimicking phantom containing an inclusion has been constructed. Frequency-domain measurements have been performed in an anechoic chamber using a Vector Network Analyser arrangement to obtain the transfer function (S21) between two antennas. Both simulations and measurements show that the HP based technique may be used for haemorrhagic stroke detection. Among linear scattering techniques, the HP based technique allows to detect dielectric inhomogeneities in the frequency domain. HP can also be used if the antennas and phantom are in free space, i.e. no coupling liquid is required. Detection of the haemorrhagic stroke has been achieved after removing the artefacts. Artefact removal is an essential step of any microwave imaging system and current artefact removal approaches have been shown to be ineffective in the specific scenario of brain imaging. However, one of this paper’s novel contributions is the proposal of an artefact removal algorithm based on a subtraction between S21 obtained using measurements, which achieves improved performance while having a much lower computational complexity

A Phantom Investigation to Quantify Huygens Principle Based Microwave Imaging for Bone Lesion Detection

This paper demonstrates the outcomes of a feasibility study of a microwave imaging procedure based on the Huygens principle for bone lesion detection. This study has been performed using a dedicated phantom and validated through measurements in the frequency range of 1–3 GHz using one receiving and one transmitting antenna in free space. Specifically, a multilayered bone phantom, which is comprised of cortical bone and bone marrow layers, was fabricated. The identification of the lesion’s presence in different bone layers was performed on images that were derived after processing through Huygens’ principle, the S21 signals measured inside an anechoic chamber in multi-bistatic fashion. The quantification of the obtained images was carried out by introducing parameters such as the resolution and signal-to-clutter ratio (SCR). The impact of different frequencies and bandwidths (in the 1–3 GHz range) in lesion detection was investigated. The findings showed that the frequency range of 1.5–2.5 GHz offered the best resolution (1.1 cm) and SCR (2.22 on a linear scale). Subtraction between S21 obtained using two slightly displaced transmitting positions was employed to remove the artefacts; the best artefact removal was obtained when the spatial displacement was approximately of the same magnitude as the dimension of the lesio

ß-decay studies of states in 12C

5 pags., 1 fig., 1 tab. -- International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX, June 25-30 2006, CERN, Geneva, SwitzerlandThe interest in experimental studies of the 12C nucleus is partly due to the astrophysical interest in its spectroscopic properties, which determine the triple alpha reaction rate, and partly motivated by the structure of this nucleus, which is not fully explained theoretically. Some aspects are described in the shell model and others by a cluster structure of three alpha particles, but both cannot so far be combined in a unified model. New experiments have been performed to address these problems. The focus of this work is on an implantation experiment, which took place in April 2006 at KVI

Antenatal care and perinatal outcomes in Kwale district, Kenya

<p>Abstract</p> <p>Background</p> <p>The importance of antenatal care (ANC) for improving perinatal outcomes is well established. However access to ANC in Kenya has hardly changed in the past 20 years. This study aims to identify the determinants of attending ANC and the association between attendance and behavioural and perinatal outcomes (live births and healthy birthweight) for women in the Kwale region of Kenya.</p> <p>Method</p> <p>A Cohort survey of 1,562 perinatal outcomes (response rate 100%) during 2004–05 in the catchment areas for five Ministry of Health dispensaries in two divisions of the Kwale region. The associations between background and behavioural decisions on ANC attendance and perinatal outcomes were explored using univariate analysis and multivariate logistic regression models with backwards-stepwise elimination. The outputs from these analyses were reported as odds ratios (OR) with 95% confidence intervals (CI).</p> <p>Results</p> <p>Only 32% (506/1,562) of women reported having any ANC. Women with secondary education or above (adjusted OR 1.83; 95% CI 1.06–3.15) were more likely to attend for ANC, while those living further than 5 km from a dispensary were less likely to attend (OR 0.29; 95% CI 0.22–0.39). Paradoxically, however, the number of ANC visits increased with distance from the dispensary (OR 1.46; 95% CI 1.33–1.60). Women attending ANC at least twice were more likely to have a live birth (vs. stillbirth) in both multivariate models. Women attending for two ANC visits (but not more than two) were more likely to have a healthy weight baby (OR 4.39; 95% CI 1.36–14.15).</p> <p>Conclusion</p> <p>The low attendance for ANC, combined with a positive relationship between attendance and perinatal outcomes for the women in the Kwale region highlight the need for further research to understand reasons for attendance and non-attendance and also for strategies to be put in place to improve attendance for ANC.</p