Biomedical signal filtering for noisy environments

 Luke\u27s work addresses issue of robustly attenuating multi-source noise from surface EEG signals using a novel Adaptive-Multiple-Reference Least-Means-Squares filter (AMR-LMS). In practice, the filter successfully removes electrical interference and muscle noise generated during movement which contaminates EEG, allowing subjects to maintain maximum mobility throughout signal acquisition and during the use of a Brain Computer Interface

Cardiovascular Magnetic Resonance Imaging for the Investigation of Patients with Coronary Heart Disease

Objectives To evaluate the role of stress perfusion cardiovascular magnetic resonance (CMR) in the investigation of stable coronary artery disease (CAD). Background Coronary artery disease remains the biggest cause of morbidity and mortality. The multi-parametric CMR examination is established as an investigative strategy for the investigation of CAD. Methods Study 1 & 2: Patients with stable coronary artery disease underwent a multi-parametric CMR protocol assessing 4 components: i) left ventricular function; ii) myocardial perfusion; iii) viability (late gadolinium enhancement (LGE)) and iv) coronary magnetic resonance angiography (MRA). The diagnostic accuracy of the individual components were assessed. The ischaemic burden of stress CMR Vs. Single Photon Emission Computed Tomography (SPECT) was determined. Study 3: Volunteers and patients were scanned with perfusion sequence which adapts the spatial resolution to the available scanning time and field-of-view. Study 4: A multi-centre pragmatic randomised controlled trial of patients with stable angina comparing CMR guided-care Vs. SPECT guided-care Vs. National Institute of Health and Care Excellence guided-care. Results Study 1 demonstrated the stress perfusion component of the multi-parametric CMR exam was the single most important component for overall diagnostic accuracy. However, the full combined multi-parametric protocol was the optimal approach for disease rule-out, and the LGE component best for rule-in. Study 2 showed that there was reasonable agreement of the summed stress scores between CMR and SPECT (a well established investigation with significant amounts of prognostic data). In study 3, a perfusion pulse sequence which automatically adapts the acquisition sequence to the available scanning time results in spatial resolution improvement and reduction in dark rim artefact. Finally in study 4 in patients with suspected angina using CMR as an initial investigative strategy produced a significantly lower probability of unnecessary angiography compared to NICE guidance. There were similar rates of CAD detection were comparable suggesting no penalty for using functional imaging as a gatekeeper for angiography. Conclusion CMR has high diagnostic accuracy for the detection of coronary artery disease; with similar detection of ischaemic burden to established tests and can be used safely and effectively as a gate keeper to invasive coronary angiography

Cardiovascular Magnetic Resonance Imaging for the Investigation of Ischaemic Heart Disease

Introduction: Coronary artery disease (CAD) remains the number one cause of mortality worldwide; improving diagnosis and treatment is a priority. Multi- parametric cardiovascular magnetic resonance (CMR) offers quantitative assessment of the cardiovascular system with a variety of techniques allowing assessment of anatomy, function, myocardial composition and perfusion during a single scan. Aims: To assess 1.) diagnostic accuracy of visual and quantitative perfusion CMR to single-photon emission computed tomography (MPS-SPECT) in patients with left main stem CAD. 2.) the hypothesis that patients with ischaemic (ICM) and non-ischaemic cardiomyopathy (NICM) have different torsion and strain parameters 3.) development and validation of a contemporary multivariable risk model of CAD from a large population undergoing X-ray angiography. 4.) a rapid 3D mDIXON pulse sequence for image quality and quantitation of MI. 5.) T1 rho prepared (T1ρ) dark blood sequence and compare to blood nulled PSIR (BN) and standard myocardium nulled PSIR (MN) for detection and quantification of scar. Methods: Patients were recruited between 2008 and 2017. Patients in chapters 3,4,6,7 underwent multi-parametric CMR including late gadolinium enhancement (LGE) imaging at 1.5 or 3.0T. Patients in chapter 5 underwent angiography. Results: 1.) CMR demonstrated significantly higher area under the curve for detection of LMS or equivalent disease over MPS-SPECT(P=0.0001). 2.) Despite no difference in LV dimensions, EF and strain between ICM and NICM, NICM patients had significantly lower LV twist(P=0.023) and torsion(P=0.017) compared to ICM. 3.) The developed model discriminated well and was well-calibrated. Diamond and Forrester and Duke scores substantially over-predicted CAD risk, whilst CAD Consortium risk models slightly under-estimated risk. 4.) Image quality was comparable between 3D and 2D LGE(P=0.162). Time for 3D image acquisition was only 5% of the time required for a standard 2D acquisition. 5.) CNRscar-blood was significantly increased for BN and T1ρ compared to MN LGE. BN LGE demonstrated significantly higher reader confidence scores

Ballistocardiogram artifact removal from EEG signal

Diplomová práce se zabývá hybridním vyšetřením fMRI-EEG. V EEG signálu jsou přítomny dva základní artefakty, gradientní a balistokardiografický. Po odstranění gradientního artefaktu a detekce R vln v kanálu EKG byl navržen postup pro odstranění balistokardiografického artefaktu, pomocí metody odečtu artefaktového vzoru, pomocí metody ICA (metody nezávislých proměnných) a metody spojující obě uvedené. Byla vyhodnocena úspěšnost všech metod a jejich vliv na evokované potenciály v signálu EEG.Master´s thesis deals with hybrid examination fMRI-EEG. Two main artifacts are present in EEG, imaging (gradient) and ballistocardiographic. After gradient artifact removal and R wave detection in ECG channel, approach for ballistographic artifact removal was proposed, with help of artifact template subtraction method, ICA and combined method. Efficiency and influence on evoked potentials of all methods were evaluated.

Computer assisted surgery for fracture reduction and deformity correction of the pelvis and long bones

Many orthopaedic operations, for example osteotomies, are not preoperative planned. The operation result depends on the experience of the operating surgeon. In the industry new developments are not longer curried out without CAD planning or computer simulations. Only in medicine the operation technology of corrective osteotomies are still in their infant stage in the last 30 years. Two dimensional analysis is not accurate that results in operation errors in the operating room. The surgeon usually obtains the preoperative information about the current bone state by radiographs. In case of complex operations (also inserting implants) planning is required. Planning based on radiographs has some system-dependent disadvantages like small accuracy, requirement of time for corrections ( distortions due to the projection) and restrictions, if complex corrections are necessary. Today the computer tomography is used as a solution. It is the only modality that allows to reach the accuracy and the resolution required for a good 3D-planning. However its a high dose rate for the patient is the serious disadvantage. Therefore in dilemma between the low dose rate and an adequate planning the first is often preferred. However in future it is expected that good operation results are guarantied only with implementation of 3D-planung. MR systems provide image information too, from which indirectly bones can be extracted. But due to their large distortions (susceptibility, non non-homogeneity of magnetic field), small spatial dissolution and the high costs, it is not expected that MRI represents an alternative in next time. The solution is the use of other image modalities. Ultrasound is here a good compromise both of the costs of the accuracy. In this work I developed an algorithm, which can produce 3D bone models from ultrasonic data. They have good resolution and accuracy compared with CT, and therefore can be used for 3D planning. In the work an improved procedure for segmenting bone surfaces is realised in combination with methods for the fusion for a three-dimensional model. The novelty of the presented work is in new approaches to realising an operation planning system, based on 3D computations, and implementing the intraoperative control by a guided ultrasound system for bone tracking. To realise these ideas the following tasks are solved: - bone modelling from CT data; - real-time extraction of bone surfaces from ultrasound imaging; - tracking the bone with respect to CT bone model. - integrating and implementing the above results in the development of an operation planning system for osteotomy corrections that supports on-line measurements, different types of deformity correction, a bone geometry design and a high level of automation. The developed osteotomy planning system allows to investigate the pathology, makes its analysis, finds an optimal way to realise surgery and provides visual and quantitative information about the results of the virtual operation. Therefore, the implementation of the proposed system can be considered as an additional significant tool for the diagnosis and orthopaedic surgery. The major parts of the planning system are: bone modelling from 3D data derived from CT, MRI or other modalities, visualisation of the elements of the 3D scene in real-time, and the geometric design of bone elements. A high level of automation allows the surgeon to reduce significantly the time of the operation plane development

Modeling of Magnetic Resonance Influence upon ECG and VCG Signal Diagnostic Quality

Cílem této diplomové práce je kvantitativní analýza příznaků vlivu magnetické rezonance na kvalitu signálů EKG a VKG. V teoretické části práce je v základu popsána elektrická aktivita srdce a záznam této aktivity pomocí elektrokardiogramu (EKG) a jeho transformace na vektorkardiogram (VKG). Teoretická část dále popisuje známé metody pro analýzu vlivu magnetické rezonance na deformaci EKG a VKG signálu. V praktické části práce je pak navržen detektor QRS komplexu pro signály EKG snímané vně i uvnitř magnetické rezonance Detektor je realizován pomocí analýzy nezávislých komponent. Pro splnění cíle práce bylo nutné vytvořit datovou bázi EKG a VKG signálů, snímaných vně i uvnitř MR. VKG signály byly získány čtyřmi transformačními metodami – Korsovo regresní, inverzní Dowerovo, Levkovo a QLSV. Signály EKG, QRS komplexy a VKG křivky byly následně podrobeny analýze. K posouzení změn bylo využito statistických ukazatelů korelační koeficient, MSE, RMSE a MAE. K posouzení VKG křivek parametry vektor křivosti křivky, maximální velikost vektoru QRS smyčky, maximální vzdálenost QRS smyčky a jejího těžiště a obvod QRS smyčky.The aim of this diploma thesis is a quantitative analysis of the symptoms of the effect of magnetic resonance on the quality of ECG and VCG signals. The theoretical part of the thesis basically describes the electrical activity of the heart and the recording of this activity using an electrocardiogram (ECG) and its transformation into a vector cardiogram (VCG). The theoretical part further describes known methods for the analysis of the effect of magnetic resonance on the deformation of the ECG and VCG signal. In the practical part of the work, a QRS complex detector is designed for ECG signals sensed outside and inside the magnetic resonance. The detector is realized by analyzing independent components. To meet the goal of the work, it was necessary to create a database of ECG and VCG signals, scanned outside and inside the MR. VCG signals were obtained by four transformation methods - Kors regression, inverse Dower, Levkov and QLSV. ECG signals, QRS complexes and VCG curves were subsequently analyzed. The statistical indicators correlation coefficient, MSE, RMSE and MAE were used to assess the changes. To assess VCG curves, the parameters of the curvature vector of the curve, the maximum size of the QRS loop vector, the maximum distance of the QRS loop and its center of gravity and the circumference of the QRS loop.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

Advanced Applications of Cardiac Computed Tomography for the Difficult-to-Image Patient

Throughout the development of computed tomographic (CT) imaging the challenges of capturing the heart, with its perpetual, vigorous motion, and in particular the tiny detail within the coronary arteries, has driven technological progress. Today, CT is a widely used and rapidly growing modality for the investigation of coronary artery disease, as well as other cardiac pathology. However, limitations remain and particular patient groups present a significant challenge to the CT operator. This thesis adds new knowledge to the assessment of these difficult-to-image patients. It considers patients with artefact from coronary artery calcification or stents, examining the remarkable diagnostic performance of high definition scanning, as well as material subtraction techniques using dual energy CT, alongside ways in which current technology might be revisited and refined with the use of alternative image reconstruction methods. Patients with challenging heart rate or rhythm abnormalities are considered in three studies; how to achieve diagnostic image quality in atrial fibrillation, the safety of an aggressive approach to intravenous beta-blocker use prior to coronary imaging, and the development of patient information to address anxiety as a source of tachycardia and motion artefact. Finally, the novel application of a single source, dual energy CT scanner to additional cardiac information is considered, with studies of myocardial perfusion CT and delayed iodine enhancement imaging, to identify ways in which non-coronary imaging might be exploited to more thoroughly evaluate a patient’s coronary artery status. These findings are presented in the context of developing technology and together offer a range of potential options for operators of cardiac CT when faced with a difficult-to-image patient

Simultaneous EEG-fMRI : novel methods for EEG artefacts reduction at source

This thesis describes the development and application of novel techniques to reduce the EEG artefacts at source during the simultaneous acquisition of EEG and fMRI data. The work described in this thesis was carried out by the author in the Sir Peter Mansfield Magnetic Resonance Centre, School of Physics & Astronomy at the University of Nottingham, between October 2010 and January 2013. Large artefacts compromise EEG data quality during simultaneous fMRI. These artefact voltages pose heavy demands on the bandwidth and dynamic range of EEG amplifiers and mean that even small fractional variations in the artefact voltages give rise to significant residual artefacts after correction, which can easily swamp signals from brain activity. Therefore any intrinsic reduction in the magnitude of the artefacts would be highly advantageous, allowing data with a higher bandwidth to be acquired without amplifier saturation, and facilitating improved detection of brain activity. This thesis firstly explores a new method for reducing the gradient artefact (GA), which is induced in EEG data recorded during concurrent MRI, by investigating the effects of the cable configuration on the characteristics of the GA. This work showed that the GA amplitude and its sensitivity to movement of the cabling is reduced by minimising wire loop areas in the cabling between the EEG cap and amplifier. Another novel approach for reducing the magnitude and variability of the artefacts is the use of an EEG cap that incorporates electrodes embedded in a reference layer, which has a similar conductivity to tissue and is electrically isolated from the scalp. With this arrangement, the artefact voltages produced on the reference layer leads are theoretically similar to those induced in the scalp leads, but neuronal signals are not detected in the reference layer. Therefore taking the difference of the voltages in the reference and scalp channels should reduce the artefacts, without affecting sensitivity to neuronal signals. The theoretical efficacy of artefact correction that can be achieved by using this new reference layer artefact subtraction (RLAS) method was investigated. This was done through separate electromagnetic simulations of the artefacts induced in a hemispherical reference layer and a spherical volume conductor in a time-varying magnetic field and the results showed that similar artefacts are induced on the surface of both conductors. Simulations are also performed to find the optimal design for an RLAS system, by varying the geometry of the system. A simple experimental realisation of the RLAS system was implemented to investigate the degree of artefact attenuation that can be achieved via RLAS. Through a series of experiments on phantoms and human subjects, it is shown here that RLAS significantly reduces the GA, pulse (PA) and motion (MA) artefacts, while allowing accurate recording of neuronal signals. The results indicate that RLAS generally outperforms the standard artefact correction method, average artefact subtraction (AAS), in the removal of the GA and PA when motion is present, while the combination of RLAS and AAS always produces higher artefact attenuation than AAS alone. Additionally, this work demonstrates that RLAS greatly attenuates the unpredictable and highly variable MA that are very hard to remove using post-processing methods

Reduction of mobile phone interference in tele-ECG monitoring.

by Hung King Fai Kevin.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 82-85 (2nd gp.)).Abstracts in English and Chinese.ACKNOWLEDGEMENT --- p.iiABSTRACT --- p.iii摘要 --- p.vTABLE OF CONTENTS --- p.viChapter CHAPTER 1 --- INTRODUCTION --- p.1Chapter 1.1 --- OBJECTIVES --- p.1Chapter 1.2 --- NEED FOR PATIENT-MONITORING SYSTEM --- p.1Chapter 1.2.1 --- Aging Population --- p.1Chapter 1.2.2 --- Increasing Population with Heart Diseases --- p.2Chapter 1.3 --- ECG BASICS --- p.3Chapter 1.4 --- EXISITING ECG-MONITORING TECHNOLOGIES --- p.4Chapter 1.5 --- CHALLENGES IN PATIENT-MONITORING --- p.5Chapter 1.6 --- DEVELOPMENT OF AN ECG-MONITORING SYSTEM --- p.6Chapter 1.6.1 --- Overall Structure --- p.6Chapter 1.6.2 --- Considerations --- p.7Chapter CHAPTER 2 --- EMI FILTERS IN ECG ACQUISITION CIRCUIT --- p.8Chapter 2.1 --- OVERVIEW OF NOISE SOURCES IN ECG ACQUISITION --- p.8Chapter 2.1.1 --- Other Biopotentials --- p.8Chapter 2.1.2 --- Motion Artifact --- p.8Chapter 2.1.3 --- Power-line Interference --- p.10Chapter 2.1.4 --- High-Frequency Electromagnetic Interference --- p.15Chapter 2.2 --- EMI FILTERS --- p.16Chapter 2.2.1 --- Introduction to EMI Filters --- p.16Chapter 2.2.2 --- Types of EMI Filter --- p.17Chapter 2.2.3 --- EMI Filters in ECG Monitoring --- p.21Chapter 2.3 --- MODELING OF INTERFERENCE IN ECG-MONITORING SYSTEM --- p.22Chapter 2.3.1 --- Model and Parameters --- p.22Chapter 2.3.2 --- Method --- p.24Chapter 2.3.2 --- Results --- p.27Chapter 2.3.3 --- Discussion --- p.30Chapter 2.4 --- BUILDING AN ECG ACQUISITION CIRCUIT WITH EMI FILTERS --- p.30Chapter 2.4.1 --- Purpose --- p.30Chapter 2.4.2 --- Experimental Setup and Method --- p.30Chapter 2.4.3 --- Results --- p.32Chapter 2.4.4 --- Discussion --- p.46Chapter CHAPTER 3 --- ADAPTIVE FILTER --- p.48Chapter 3.1 --- OBJECTIVE --- p.48Chapter 3.2 --- INTRODUCTION TO ADAPTIVE FILTER --- p.48Chapter 3.3 --- METHOD --- p.50Chapter 3.4 --- RESULTS --- p.52Chapter 3.5 --- DISCUSSION --- p.57Chapter CHAPTER 4 --- WAP-BASED TELEMEDICINE APPLICATIONS --- p.59Chapter 4.1 --- INTRODUCTION TO TELEMEDICINE --- p.59Chapter 4.2 --- INTRODUCTION TO WAP --- p.59Chapter 4.3 --- WAP APPLICATIONS --- p.60Chapter 4.4 --- SYSTEM IMPLEMENTATION --- p.63Chapter 4.4.1 --- Overall Structure --- p.63Chapter 4.4.2 --- Relational Database --- p.63Chapter 4.4.3 --- Program Flow --- p.64Chapter 4.4.4 --- ECG Browsing and Feature Extraction --- p.70Chapter 4.5 --- EMULATION --- p.72Chapter 4.6 --- EXPERIENCE WITH WAP PHONE --- p.74Chapter 4.7 --- DISCUSSION AND CONCLUSION --- p.75Chapter CHAPTER 5: --- CONCLUSION AND FUTURE WORK --- p.77Chapter 5.1 --- CONCLUSION --- p.77Chapter 5.2 --- FUTURE WORK --- p.77Chapter 5.3 --- MARKET ANALYSIS --- p.79BIBLIOGRAPHY --- p.8