Electric Impedance Tomography (EIT) is a promising medical imaging technique that reconstructs the internal conductivity of an object from boundary measurements. EIT is currently being used to monitor the lung during ventilation clinically. Amongst other suggested uses for imaging it can also be used to image neuronal function. There are different ways on how EIT can image neuronal function and two of these are tested in this thesis. The overall aim of our work was to advance imaging of physiological and pathological neuronal activity using EIT and assess its potential for future clinical use. In Chapter 1, a general introduction into brain imaging techniques and EIT is given. In Chapter 2, the effect of different anaesthetics on the neuronal signal was assessed to prepare for EIT recordings under anaesthesia. In Chapter 3, we assessed the validity of two biophysical models regarding the behaviour of the impedance in response to alterations in the carrier frequency experimentally. This allowed an assessment of the ideal carrier frequency to image physiological neuronal activity. In Chapter 4, the source of the fast neural signal in EIT is discussed further. In Chapter 5, the possibility of imaging physiological neuronal activity throughout the brain is tested and its limitations are discussed. In Chapter 6, the impedance response to epileptiform activity is characterized and the potential use of EIT in imaging epileptic foci in epilepsy patients is discussed. In Chapter 7, imaging of epileptic foci in subcortical structures is tested using two different ways of imaging with EIT.

Objective: To investigate the role of hybrid 18F-FDG PET/CT as a potential risk-stratification tool of aneurysm expansion by measuring metabolic activity on PET and textural analysis on CT in abdominal aortic aneurysm (AAA). Histological markers of AAA wall inflammatory cell infiltrate and enzymatic degradation have been associated with increased 18F-Fluorodeoxyglucose (18F-FDG)-Positron Emission Tomography /Computed Tomography (PET/CT) uptake. Methods: Fifty patients with asymptomatic infrarenal AAA enrolled under surveillance at one of our institutions underwent 18F-FDG-PET/CT. Seventeen subjects were investigated for increased glucolysis in the AAA wall and optimal circulation imaging time for 18F-FDG. In 25 subjects the relationship between aneurysm metabolic activity and expansion was explored. Forty subjects had AAA CT textural analysis (CTTA) parameters performed on the CT component of PET/CT and were studied in relation to aneurysm expansion. Twenty-four subjects had circulating biomarkers analysed. Whole vessel assessment, region of interest analysis and the role of correcting for background blood pool activity were explored. Results: Thirteen of seventeen subjects investigated for increased 18F-FDG uptake had an AAA wall SUVmax > 2.5. In 17 subjects assessed for optimal circulation imaging time for 18F-FDG, no significant advantage in imaging at 3h over 1h after 18F-FDG injection was observed. 18F-FDG uptake correlated inversely with future AAA expansion in the preliminary group of 25 patients and in 40 subjects who also had CTTA. In subjects who had CTTA, coarse texture showed an inverse association with 18F-FDG uptake and medium coarse texture correlated with future AAA expansion. In 24 AAA patients who had serum biomarker assays, significantly higher levels of high sensitivity matrix metalloproteinase-9 (hsMMP-9) and hsMMP-2 compared to healthy controls were found. There was no correlation between AAA 18F-FDG uptake and levels of hsMMP-9, hsMMP-2, hs-interferon-γ and hs-C-reactive protein. Conclusions: In-vivo 18F-FDG PET/CT data indicated that small AAA show increased glucose metabolism. Relationships between AAA 18F-FDG uptake, CTTA and future expansion were identified. AAA18F-FDG PET/CT shows potential to identify subjects at risk of significant expansion. AAA metabolism may not relate to serum levels of certain inflammatory biomarkers.

Introduction: Idiopathic pulmonary fibrosis (IPF) is characterised by excessive deposition of extracellular matrix proteins and destruction of the lung architecture. The aetiology of this disorder is unknown and few effective therapies are available. Several models have been established to identify key pathological cells and mediators that may be important in IPF, however these models lack the classical histopathological features seen in IPF, such as fibrotic foci. The aim of this project was to develop a novel 3-D in vitro assay system which more closely mimics a fibrotic focus, for pre-clinical drug evaluation. Methods: Primary human lung fibroblasts were isolated as outgrowths from small (<1 mm3) lung explants (non-IPF and IPF patients). Non-IPF (n = 10) and IPF (n = 10) fibroblasts were cultured in non- adherent 96-well plates to generate fibroblastic spheroids. Spheroid formation and phenotypic features were characterised using time-lapse videomicroscopy, histological analysis, (including TUNEL assay) and, electron microscopy. RNA was extracted from the spheroids and microarray analysis and qRT-PCR were used to analyse mRNA levels. Total collagen was measured using HPLC analysis of hydroxyproline levels while active TGFβ within the spheroid homogenates and supernatants were measured using the transformed mink lung epithelial cell bioassay. A medium-throughput screen of potential anti-fibrotic compounds (using a focused GSK compound library known as the fibrosis toolbox) was also performed, using hydroxyproline levels as the endpoint measure. Results: Non-IPF and IPF fibroblasts were able to form non-proliferating spheroids within 24 hours of incubation, with clear organisation and orientation of cells within the spheroid. IPF spheroids had a myofibroblastic phenotype with increase expression of αSMA. TUNEL assay identified increased numbers of apoptotic cells in non-IPF spheroids in comparison to IPF spheroids, which may be due, in part, to autocrine/paracrine COX1-mediated PGE2 generation. The mink lung cell assay demonstrated that non-IPF and IPF spheroids spontaneously produced high levels of active TGFβ, which was partially dependent on β3 and β8 integrins. Antagonising TGFβ signalling did not however affect spheroid collagen production. Microarray data analysis illustrated a limited number of differentially expressed genes, with the majority involved in encoding proteins that play a key role in metabolic pathways. The fibrosis toolbox identified potential target molecules that impact on collagen biosynthesis including EP2/4 compounds, an integrin αv inhibitor, Smo antagonists, MCP-1 inhibitor, and mTORC 1/2 inhibitors. Conclusions: Fibrotic fibroblast spheroids mimic some of the key characteristics of fibroblasts in fibrotic foci of IPF lungs (i.e. increased collagen production, elevated levels of active TGFβ and resistance to apoptosis). In addition, microarray and medium-throughput screening identified several potential targets. Therefore, fibrotic fibroblast spheroids may represent a novel assay system for pre-clinical drug evaluation, and warrant further investigation.

Multifrequency Electrical Impedance Tomography (MFEIT) is an emerging imaging modality which exploits the dependence of tissue impedance on frequency to recover images of conductivity. Given the low cost and portability of EIT scanners, MFEIT could provide emergency diagnosis of pathologies such as acute stroke, brain injury and breast cancer. Whereas time-difference, or dynamic, EIT is an established technique for monitoring lung ventilation, MFEIT has received less attention in the literature, and the imaging methodology is at an early stage of development. MFEIT holds the unique potential to form images from static data, but high sensitivity to noise and modelling errors must be overcome. The subject of this doctoral thesis is the investigation of novel techniques for including spectral information in the image reconstruction process. The aim is to improve the ill-posedness of the inverse problem and deliver the first imaging methodology with sufficient robustness for clinical application. First, a simple linear model for the conductivity is defined and a simultaneous multifrequency method is developed. Second, the method is applied to a realistic numerical model of a human head, and the robustness to modelling errors is investigated. Third, a combined image reconstruction and classification method is developed, which allows for the simultaneous recovery of the conductivity and the spectral information by introducing a Gaussian-mixture model for the conductivity. Finally, a graph-cut image segmentation technique is integrated in the imaging method. In conclusion, this work identifies spectral information as a key resource for producing MFEIT images and points to a new direction for the development of MFEIT algorithms.

In clinical cardiology, different imaging technologies can be used to assess cardiac anatomy, ventricular function and focal myocardial disease. Cardiovascular magnetic resonance (CMR) using late gadolinium enhancement (LGE) is the gold standard non-invasive method for focal myocardial tissue characterisation. However it has limitations, including not allowing quantification of the extracellular volume (ECV) or assessment of diffuse processes. In this thesis, these shortcomings were addressed using novel CMR T1 based methodologies. In early work, the ECV was assessed in health and a variety of cardiac diseases. It was found to be elevated in dilated and hypertrophic cardiomyopathy and aortic stenosis – diseases where diffuse fibrosis is known to occur. There was a more marked ECV elevation in cardiac AL amyloidosis. Further work assessed a potential role for pre contrast T1 in Anderson Fabry disease, finding that it detects disease at an earlier stage than any other imaging marker and is diagnostic of this disease in patients with left ventricular hypertrophy. In patients with iron overload, the T1 was found to strongly correlate with the previous non-invasive gold standard test of CMR T2*. However the T1 appeared to be more sensitive for the detection of earlier disease. Lastly, pilot technical development work evaluated new and faster methods for ECV and T1 assessment and suggested a potential role for this technique in other body organs. The above results were particularly notable in Anderson Fabry disease, iron overload and cardiac amyloidosis. In the case of Anderson Fabry disease and cardiac amyloidosis, sphingolipid and amyloid deposition respectively cannot be measured using current non-invasive clinical techniques. In conclusion, this work has pioneered the use of novel tissue characterisation techniques which have potential roles in earlier diagnosis, pathophysiological insights, prognostication and therapy monitoring in cardiac disease. This will ultimately provide benefit to patients with cardiac disease.

A pixellated High Purity Germanium Compton camera has been developed at the University College London (UCL) for nuclear medicine studies using two planar detectors which both have 4×4mm2 position sensitivity for each pixel. The potential benefits of this imaging system lie with a wider field of view, 3D image reconstruction without tomography, and portability. This thesis presents the use of split (charge sharing) events, which occur at the interpixel area between adjacent pixels, to enhance the spatial resolution from 4mm to 0.5mm for lateral positioning. In addition, this method increases the system efficiency, resulting in more photons in the reconstructed image for a given integration time. The Compton camera has a unique planar orientation of 152 scatter pixels at the front and 25 absorber pixels at the back. The two detectors are separated by 9.6cm apart in the same vacuum housing. The camera was built by ORTEC and (Gamma Ray Tracking 4 channel) GRT4 cards were employed to control the data acquisition. The spatial resolution improvement was evaluated theoretically and experimentally using simulated and experimental reconstructed images. The camera’s overall spatial resolution was estimated theoretically to be 5mm intrinsic and 1.8mm after using split events for a 662keV gamma ray placed at 2.5cm from scatter detector. The equivalent the experimental result showed a FWHM of 2.2mm. The camera was also evaluated using different isotopes and phantoms from points, line and simulated clinical anthropomorphic distributed sources. In conclusion, according to the mathematical calculation, the geometrical spatial resolution profoundly affects the overall spatial resolution. However, utilising split events has enhanced the spatial resolution to submillimetre and increased the efficiency by 30%. Including split events as a high spatial resolution knowledge of source positioning has improved reconstructed images. The current system limitations include offline data processing, slow data transfer rate and limited readout electronics.

Adenocarcinoma of the pancreas is one of the top ten leading causes of cancer deaths. In the UK approximately 8000 people are diagnosed with the disease each year. Surgical resection is the only chance of cure and is only possible in a minority of patients. Even after resection, median survival is only 10–20 months and no more than 5–20% of resected patients survive five years. Earlier diagnostic assays and novel treatments are urgently required to improve outcomes. Chapter 1 summarises clinical aspects of pancreatic cancer and current diagnostic and prognostic tests. Chapter 2 gives an introduction to the cell cycle, initiation of DNA replication, cell cycle checkpoints and how exploitation of these mechanisms can result in selective death of cancer cells. Chapter 3 describes an analysis of four cell cycle proteins - Mcm2, geminin, phosphohistone H3 and Cdc7 - using immunohistochemistry of archived FFPE tissue from patients with pancreatic cancer. Linked clinicopathological variables were used to attempt to predict outcome and to validate Cdc7 as a potential target in the treatment of pancreatic cancer. Chapter 4 describes cell culture techniques that were used to grow pancreatic adenocarcinoma and IMR-90 fibroblast cell lines in the laboratory. Cells were treated with siRNA against CDC7 and a small molecule inhibitor of Cdc7/Cdk9. A variety of techniques including FACS analysis, western blotting, BrdU labelling and apoptosis assays were used to assess the effects of these treatments. Chapter 5 describes the methods and early results obtained from using a novel Mcm5 assay for the determination of malignancy in biliary brushings. Chapter 6 discusses the main conclusions drawn from the work as well as potential future studies.

Sickle cell disease (SCD) is known to be a prothrombotic condition; this is also true for combined hormonal contraceptives (HC), which increases the thrombotic risks in their users. Recently, Sickle Cell Trait (SCT) has been reported to carry increased risks of thrombosis Nonetheless, HC methods are efficacious and widely used while, pregnancy carries major risks for SCD women. Hence, there is a need for robust evidence about the safety or risks of HC in SCD and SCT to aid in the choice of contraceptive methods for these women. This study aimed to test the hypothesis that there are no additional clinical or haematological risks to SCD patients and women with SCT using hormonal contraceptive methods that is over and above those inherent in their SCD and SCT status. This is a multi-­‐centre, prospective cohort study, which looked at and compared clinical complications, haemostatic and haematological markers in 68 women with SCD, 22 women with SCT and 27 similar women with normal haemoglobin. In conclusion a two year follow-­‐up of women with SCD using Combined Oral Contraception (COC) found no incidence of Venous Thrombo Embolism (VTE) in these women and the occurrence of other clinical complications, such as sickle-­‐cell crises, the need for blood transfusion and hospital admissions were minimal. It also demonstrated that these complications are comparable to women with normal haemoglobin using COC. Also the use of COC in women with SCD did not significantly alter the haemostatic markers studied, nor did it adversely affect their liver function or exacerbate any inflammatory changes. Progestogen only contraception (POC) use is associated with an increased incidence of menstrual irregularities which are not significantly different from those noted in women with normal haemoglobin taking POC. SCT women manifested increased prothrombotic tendencies, which are more marked in women using COC, while women with 4 normal haemoglobin showed increased inflammatory and endothelial activation markers regardless of the type of contraception used.

Serological methods to differentiate recent from non-recent HIV infections were introduced to routine surveillance in Poland, Estonia and Ukraine, to estimate HIV incidence and to characterise those newly-diagnosed and infected. Establishing the characteristics of populations at greatest risk of HIV enables appropriate and target prevention and intervention strategies to be developed, reducing risk of onward transmission. Using existing testing services within each country, residual samples from newly-diagnosed persons were tested for evidence of recent infection using an avidity assay. Data were collated in 2013-2014 using modified existing methods in Kiev City, Poland, and Estonia. Diagnosis rates for Kiev City, Poland and Estonia were 21.5, 1.2 and 29.7 per 100,000 population, respectively. Incidence estimates for Kiev City were 21.5 per 100,000 population, with 6.5% classified as recent. The disproportionate distribution of HIV were among men who have sex with men (MSM) and persons who inject drugs (PWID) was evident. Uncorrected estimates for Poland and Estonia were 30% and 44%, respectively. This work enables targeted public health action and health promotion work to be made, laying the foundation for local and national guidelines.

Many clinical procedures involve the use of minimally invasive devices such as needles and catheters. Providing increased information about tissues that are adjacent to the device tips could reduce the probability of complications in these procedures. Optical fibres are well suited for integration into medical devices and they can be used to provide information relevant to tissue characterisation. This dissertation is centred on the integration of optical fibres into needles and catheters to obtain information about haemoglobin. In two studies, reflectance spectroscopy was performed. Two optical fibre geometries were tested, and for each, Monte Carlo simulations were used to estimate the reflectance values and the pho- ton penetration depths. In the first study, reflectance spectroscopy was performed with a double clad fibre. Experiments using expired human red blood cells were performed to determine the sensitivity of the measurements to oxygen saturation variation at physiological levels. Distinction between normal oxygen saturation values in veins and arteries was possible, making this fibre potentially useful to verify needle placement during a venous catheterisation or during a transseptal puncture. In the second study, two polymer optical light fibres were directly integrated into an epidural catheter. This optical catheter was tested during an ex-vivo swine laminectomy in the lumbar region. Another ex-vivo experiment was performed on chicken wings to discern blood vessels from other tissues. This information could be used during anaesthesic procedures to reduce the risk of toxicity from an intravascular injection. With reflectance spectroscopy, the depth in tissue from which signal is obtained is limited by the inter-fibre distance. This limitation motivated a third study, in which photoacoustic imaging was used to obtain image contrast for haemoglobin. The results of the three studies suggest that the integration of optical fibres into medical devices during minimally invasive procedures can allow for clinically relevant measurements of tissue properties in real-time.