Image reconstruction in electrical impedance mammography

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A kit-based aluminium-[18F]fluoride approach to radiolabelled microbubbles

The production of 18F-labelled microbubbles (MBs) via the aluminium-[18F]fluoride ([18F]AlF) radiolabelling method and facile inverse-electron-demand Diels-Alder (IEDDA) ‘click’ chemistry is reported. An [18F]AlF-NODA-labelled tetrazine was synthesised in excellent radiochemical yield (>95% RCY) and efficiently conjugated to a trans¬-cyclooctene (TCO) functionalised phospholipid (40-50% RCY), which was incorporated into MBs (40-50% RCY). To demonstrate the potential of producing 18F-labelled MBs for clinical studies, we also describe a kit-based approach which is amenable for use in a hospital radiopharmacy setting

Enhanced pre-operative axillary staging using intradermal microbubbles and contrast-enhanced ultrasound to detect and biopsy sentinel lymph nodes in breast cancer: a potential replacement for axillary surgery.

OBJECTIVE: To compare the experience of four UK Centres in the use of intradermal microbubbles and contrast enhanced ultrasound (CEUS) to pre-operatively identify and biopsy sentinel lymph nodes (SLN) in patients with breast cancer. METHODS: In all centres, breast cancer patients had a microbubble/CEUS SLN core biopsy prior to axillary surgery and patients in Centres 1 and 2 had a normal greyscale axillary ultrasound. Data were collected between 2010 and 2016; 1361 from Centre 1 (prospective, sequential), 376 from Centre 2 (retrospective, sequential), 121 from Centre 3 (retrospective, selected) and 48 from Centre 4 (prospective, selected). RESULTS: SLN were successfully core biopsied in 80% (Centre 1), 79.6% (Centre 2), 77.5% (Centre 3) and 88% (Centre 4). The sensitivities to identify all SLN metastases were 46.9% [95% confidence intervals (CI) (39.4-55.1)], 52.5% [95% CI (39.1-65.7)], 46.4% [95% CI (27.5-66.1)] and 45.5% [95% CI (16.7-76.6)], respectively. The specificities were 99.7% [95% CI (I98.9-100)], 98.1% [95% CI (94.5-99.6)], 100% [95% CI (93.2-100%)] and 96.3% [95% CI (81-99.9)], respectively.The negative predictive values were 87.0% [95% CI (84.3-89.3)], 84.5% [95% CI (78.4-89.5)], 86.9% [95% CI (82.4-90.3)] and 86.2% [95% CI (78.4-91.5)], respectively. At Centres 1 and 2, 12/730 (1.6%) and 7/181 (4%), respectively, of patients with a benign microbubble/CEUS SLN core biopsy had two or more lymph node (LN) macrometastases found at the end of primary surgical treatment. CONCLUSION: The identification and biopsy of SLN using CEUS is a reproducible technique. Advances in knowledge: In the era of axillary conservation, microbubble/CEUS SLN core biopsy has the potential to succeed surgical staging of the axilla

Preliminary results from an EIT breast imaging simulation system

Output reports results used as basis for a patent (“Apparatus and Method for Detecting Abnormalities in Bodily Matter” 6,856,824 B1 Jan 2005, USA) of Electrical Impedance Mammography (EIM). Using clinical results the sensitivity and specificity related information of the technique to early stage breast cancers were indicated. Furthermore it was shown that EIM was capable of providing images from, and analysis of, breast tissues for pre-menopausal females. These findings and associated system design indicators led to funding from Questor Lachesis “EIM” (LF2005/£250k)/(www.lachesisfund.com) leading towards the first human clinical trials of the technology in UK

Ultrasound modulated optical tomography in optical diffuse medium using acoustic radiation force

Ultrasound modulated optical tomography (UOT) is a hybrid technique which combines optical contrast with ultrasound (US) resolution to achieve deeper tissue imaging. However, the technique is currently limited due to the weak modulation signal strength and consequently a low Signal-to-Noise Ratio (SNR). One potential way to increase the SNR of UOT is to increase the ultrasound induced particle displacement, by either increasing the ultrasound amplitude or using the acoustic radiation force (ARF). In this thesis, I theoretically studied the relationship between the scatterers‘ displacements and the modulation signal strength and experimentally investigated the ARF in addition to investigating the detrimental effects of shear wave propagation on ultrasound modulated optical (UO) signals. A Monte Carlo simulation tool was developed to investigate how the UOT signal changes with increasing amplitude of ultrasound induced particle displacement in the simulation object. By combining a realistic ultrasound field with UOT simulation, the nonlinear effect of ultrasound on UOT signal was studied for the first time. An UOT experiment system, using a CCD camera and a single element transducer driven by an amplitude-modulated (AM) ultrasound signal to generate an oscillatory ARF, was tested on a tissue mimic phantom. The effect of AM ultrasound on UO signals was investigated for the first time. It was found that with longer CCD exposure times, larger ARF induced particle movements can be captured and the UO signal was increased. Next the effects of an ARF induced shear wave on UO signals are studied. The ARF induced shear waves can propagate transversely out of the focal region and may reduce spatial resolution. This is the first examination of the time evolution of the shear wave effect generated by a short ultrasound burst on the UO signal. The spatial resolution of the system was studied by scanning the phantoms. It was found that by adjusting the timing and length of CCD exposure, shear wave effects can be minimised and both the optical and mechanical properties of the phantom can be detected and distinguished.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A comparison of methods for measurement of spatial resolution in two-dimensional circular EIT images

The literature concerning measurement of spatial resolution in electrical impedance tomography (EIT) is vague. Different groups often use their own method or a modified version of a better known method, thus hindering a generalized resolution measurement which could be useful for gauging the performance of one system against another. Measurement of spatial resolution in EIT is further complicated by its spatial variant nature and hence cannot be expressed simply with a single parameter as it can be in other imaging modalities (such as nuclear medicine or MRI for example). If the performance of each acquisition and image reconstruction system in EIT is to be compared objectively then there needs to be a common standard. In this paper the results of different methods for calculating spatial resolution are compared and an improved method is proposed which aims to fulfil this role

Ultrasound modulated optical tomography in optical diffuse medium using acoustic radiation force

Ultrasound modulated optical tomography (UOT) is a hybrid technique which combines optical contrast with ultrasound (US) resolution to achieve deeper tissue imaging. However, the technique is currently limited due to the weak modulation signal strength and consequently a low Signal-to-Noise Ratio (SNR). One potential way to increase the SNR of UOT is to increase the ultrasound induced particle displacement, by either increasing the ultrasound amplitude or using the acoustic radiation force (ARF). In this thesis, I theoretically studied the relationship between the scatterers‘ displacements and the modulation signal strength and experimentally investigated the ARF in addition to investigating the detrimental effects of shear wave propagation on ultrasound modulated optical (UO) signals. A Monte Carlo simulation tool was developed to investigate how the UOT signal changes with increasing amplitude of ultrasound induced particle displacement in the simulation object. By combining a realistic ultrasound field with UOT simulation, the nonlinear effect of ultrasound on UOT signal was studied for the first time. An UOT experiment system, using a CCD camera and a single element transducer driven by an amplitude-modulated (AM) ultrasound signal to generate an oscillatory ARF, was tested on a tissue mimic phantom. The effect of AM ultrasound on UO signals was investigated for the first time. It was found that with longer CCD exposure times, larger ARF induced particle movements can be captured and the UO signal was increased. Next the effects of an ARF induced shear wave on UO signals are studied. The ARF induced shear waves can propagate transversely out of the focal region and may reduce spatial resolution. This is the first examination of the time evolution of the shear wave effect generated by a short ultrasound burst on the UO signal. The spatial resolution of the system was studied by scanning the phantoms. It was found that by adjusting the timing and length of CCD exposure, shear wave effects can be minimised and both the optical and mechanical properties of the phantom can be detected and distinguished.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Non linear ultrasound Doppler and the detection of targeted contrast agents

One of the main challenges in molecular imaging with targeted contrast agents is the detection and discrimination of attached agents from the rest of the signals originating from freely flowing agents and tissue. The aim of this thesis was to develop methods for the detection of targeted microbubbles. One approach consisted of investigating the use of nonlinear Doppler for this purpose. Nonlinear Doppler enables the differentiation of moving from non-moving and linear from nonlinear scattering. Targeted microbubbles are static and nonlinear scatterers and they should be detected using this technique. A novel nonlinear Doppler technique: Pulse subtraction Doppler, was developed and compared to pulse inversion Doppler. It is shown that both techniques lead to similar Doppler spectra and depending on the medical applications and the equipment limitations, both techniques have benefits. This served as a starting point for the derivation of a generalised nonlinear Doppler technique, based on combined linear pulse pair sequences and tested in a simulation study. The response from a single microbubble was simulated for different pulse combinations and the pulse sequences were compared with regards to criteria specific to imaging requirements. It was shown that depending on initially set criteria, such as transmitted energy, mechanical index or scanner characteristics, certain pulse combinations offer alternatives to the current imaging modalities and allow to take into account specific constrains due to the targeted application/equipment. Furthermore, the proposed approach is directly applicable in a strict non linear imaging approach, without Doppler processing. An in vitro phantom was designed in order to assess pulse subtraction Doppler for the detection and discrimination of static nonlinear microbubbles in the presence of free flowing ones. It was shown that pulse subtraction Doppler enables such discrimination and the practicability for in vivo situations is discussed. The pulse subtraction Doppler sequences were also tested on a phantom containing magnetic bubbles. It was shown that the magnetic bubbles can be immobilised through a magnetic field to a specific region of interest under flow conditions. The bubbles also showed to be acoustically detectable and to scatter linearly at diagnostic driving pressures. Preliminary work regarding experimental biotinylated microbubbles and their attachment to streptavidin coated surfaces is also presented. Due to their proximity to a wall, researchers have found that targeted microbubbles exhibit different acoustic signatures compared to free ones and this knowledge can improve their detection techniques. The behaviour of microbubbles against a membrane of varying stiffness was also studied through high speed camera observations. It was found both experimentally and by comparison to theoretical modelling that within the stiffness range of human blood vessels the change in acoustical behaviour of microbubbles is negligible. This thesis has taken two complementary research approaches which have shown to constitute advancements for the detection and discrimination of targeted microbubbles.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Research on Short-Term Wind Power Forecasting by Data Mining on Historical Wind Resource

In order to enhance the accuracy of short-term wind power forecasting (WPF), a short-term wind power forecasting method based on historical wind resources by data mining has been designed. Firstly, the spoiled data resulting from wind turbine and meteorological monitoring equipment is eliminated, and the missing data is added by the Lomnaofski optimization model, which is based on the temporal-spatial correlation of meteorological data. Secondly, the wind characteristics are analyzed by the continuous time similarity clustering (CTSC) method, which is used to select similar samples. To improve the accuracy of deterministic prediction and prediction error, the radial basis function neural network (RBF) deterministic forecasting model was built, which can approximate nonlinear solutions. In addition, the wind power interval prediction method, combining fuzzy information granulation and an Elman neural network (FIG-Elman), is proposed to acquire forecasting intervals. The deterministic prediction of the RBF-CTSC model has high accuracy, which can accurately describe the randomness, fluctuation and nonlinear characteristics of wind speed. Additionally, the mean absolute error (MAE) and root mean square error (RMSE) are reduced by the new model. The interval prediction of FIG-Elman results show that the interval width decreased by 18.85%, and the coverage probability of interval increased by 10.94%