Clinical Applications of Electrical Impedance Tomography in Stroke and Traumatic Brain Injury

Electrical Impedance Tomography (EIT) is a medical imaging technology which uses voltage measurements on the boundaries to reconstruct internal conductivity changes. When applied to imaging brain function, EIT is challenged by the unique geometry of the head and the high variability in the conductivities of brain tissue. Stroke and Trau-matic Brain Injury (TBI) are two of the leading causes of death and long-term disability worldwide. It has been suggested that EIT, which is already in clinical use primarily as a means of assessing lung function, could be used as a pre-hospital diagnostic tool for stroke and TBI, and for bedside monitoring for brain injury patients. The main aim of this PhD thesis is to bring the application of EIT in brain injury closer to regular clinical use. Chapter 1 introduces the concepts of EIT, stroke and TBI, and provides a comprehensive review of clinically relevant neuroimaging techniques and the current state of brain EIT. Chapter 2 presents the results of a series of lab experiments designed to investigate the characteristics and mechanisms of drift in measured boundary voltages, which is the key technical barrier to brain monitoring with EIT. Ex-periments were conducted on lab phantoms, vegetable skin, and healthy human subjects. Chapter 3 describes a feasibility study of monitoring for brain injury with EIT over several hours, using noise recorded on real healthy volunteers. This study also compares the performance of different electrode types. Chapter 4 presents a clinical pilot study performed on acute stroke patients. Multi-frequency (MF) EIT data were record-ed on patients and healthy controls to create the first of its kind clinical EIT dataset to be used as a resource for future research for the EIT community. Finally, the ability to identify stroke patients is demonstrated on the clinical EIT dataset

Recent technological developments in the diagnosis and treatment of cerebral edema

Latest technological advancements in neurocritical care have translated to improved clinical outcomes and have paved the way for the effective diagnosis and treatment of cerebral edema. Effective management of cerebral edema has the potential to provide a personalized treatment by obtaining the complete pathophysiological information of the patient. The aims of this review are to inform the reader about the research and development in this field in the past decade as well as the materialization of scientific literature through patents. There is a growing interest in multimodal monitoring of the diseased brain as it provides a necessary means to implement effective intervention strategies. Although there is a gradual shift toward the adoption of noninvasive devices for research purposes, their clinical applications are hindered by their inaccuracies. However, the inherent risk of complication and high costs of implementation challenge the status quo. The role of neuroprotectants is explored and the combination of neurodiagnostic and neuroprotective approaches is proposed. Finally, the impacts of the current state of global affairs are discussed and it is predicted that the rising number of traumatic brain injury patents will inevitably translate to improvements in technologies to effectively address cerebral edema

A portable EIT system for emergency medical care

Electrical Impedance Tomography (EIT) is a medical imaging technique in which images of tissue conductivity within a body can be inferred from surface electrode measurements. The main goal of this study is to develop a portable EIT system incorporating an optimized electrode layout to detect intracranial haematomas for use in emergency care. A growing haematoma can cause severe and even permanent damage to the delicate tissue of the brain, morbidity, and eventual death of the patient. No capability is at present available for the diagnosis of haematomas pre-hospitalisation or by first-responders. The lack of this crucial information can lead to bad decisions on patient management, and in particular, where to send the patient. Blood has a high electrical conductivity contrast relative to other cranial tissue and can be detected and monitored using electrical impedance methods. EIT is a non-invasive, low-cost monitoring alternative to other imaging modalities, and has the potential to detect bleeding and to localize the approximate bleeding site. A device of this nature would reduce treatment delays, save on costs and waste, and most significantly, positively impact patient outcomes. The first step was a numerical simulation study on FE models. The full array and the hemi-array electrode layouts were modelled and the anomalies were simulated in different positions with different sizes. The results were obtained using TSVD and WMNM reconstruction methods by COMSOL linked with MATLAB. The simulated anomalies were detected for all the positions using both layouts; however those from the full array were in general superior to the hemi-array. In order to perform realistic experiments, a prototype EIT system was constructed in the laboratory. The constructed EIT has 16 channels and operates in the frequency range of 10 kHz to 100 kHz with a temporal resolution of 100 frames per second and high level of accuracy of 93.5 %. The minimum number of 8 electrodes was chosen in this study for emergency care. Minimizing the number of electrodes speeds up the electrode setup process and avoids the need to move the patient s head in emergency care. In the second part of this study, phantom experiments were performed to find an optimised electrode layout for emergency care. The full array and the hemi-array were investigated using phantom experiments. As expected, the full array layout had the best performance in general; however, the performance of the hemi-array layout was very poor. Thus a novel optimised electrode layout (semi-array) for emergency care was proposed and evaluated in phantom experiments. For the hemi-array and the semi-array layouts, measurement sensitivity depends strongly on the anomaly location since the electrodes are not placed all over the head. The HA layout performed very badly, with the best radial localization error of 0.8100 mm, compared to the SA layout with the worst error of 0.2486 mm. Some reconstructed anomalies located far from the electrodes in the posterior region were almost invisible or erroneous for the hemi-array layout; however, it is enhanced by using the semi-array layout. Finally, in vitro experiments were conducted on ovine models. In most of the experiments carried out by other researchers, since the location of the simulated anomalies was not known and the simulated blood was normally injected into the body or the head, localization of the anomalies was not considered and the quantity of the injected blood was investigated solely. In our new method of experiment, the position of the anomalies was known a priori and thus could be compared accurately to the EIT results. The full array and the semi-array layouts were compared in terms of detection, localisation and size estimation of haematomas. As expected, the full array layout was found to be more robust than the semi-array layout with the best mean value of the localization error of 0.0564 mm and the worst QI error of around 30%. Using a minimum number of electrodes in an optimised layout is always desirable in clinical applications. The semi-array 8-electrode layout prevents unnecessary movements and the electrode connections to the head would be very quick in emergency care. Although the semi-array 8-electrode layout reduced the sensitivity of the measurements, the findings from the experiments indicated its potential to detect and monitor haematomas and probably extend its application for emergency applications where the required accuracy is not critical

Design of Miniaturized Antipodal Vivaldi Antennas and a Microwave Head Imaging System for the Detection of Blood Clots in the Brain

Traditional brain imaging modalities, for example, MRI, CT scan, X-ray, etc. can provide precise and high-resolution images of the brain for diagnosing lesions, tumors or clots inside the brain. However, these modalities require bulky and expensive test setups accessible only at specialized diagnostic centers, and hence may not be suitable or affordable to many patients. Furthermore, the inherent health risks limit the usability of these modalities for frequent monitoring. Microwave imaging is deemed a promising alternative due to its being cost-effective, portable, non-ionizing, non-intrusive. Therefore, this work aims to design an effective microwave head imaging system for the detection of blood clots inside the brain. Two miniaturized antipodal Vivaldi antenna designs are proposed which can provide wideband operation covering the low microwave frequency range (within 1 - 6 GHz) while having electrically small dimensions, directional radiation pattern with reasonable gain, and without requiring immersion in any matching/ coupling liquid. A head imaging system is presented which utilizes a quarter-head scanning approach, to reconstruct four images of the brain by scanning four quarters of the head, using the designed antipodal wideband Vivaldi antenna. A numerical brain model, with and without the presence of blood clot, is simulated using the proposed head-imaging system. At each quarter, the antenna is placed at nine different positions for scanning. The reflected signal at each position is processed and using confocal microwave imaging technique four images of the brain are reconstructed. A comparison is made among the four images in terms of their intensities, for the detection and approximate location of the blood clot inside the brain. The presence of higher intensity regions in any specific quarter of the head demonstrates the presence of a clot and its location and validates the feasibility of the proposed head imaging system using the low frequency wideband Vivaldi antenna

Curierul medical. August 2015, Vol. 58, No 4

Fondatori: Ministerul Sănătăţii al Republicii Moldova, Universitatea de Stat de Medicină şi Farmacie “Nicolae Testemiţanu”From its debut in 1958, the journal has striven to support the interests of Moldovan medicine concerning the new concepts of its development. The Editorial Board warmly welcomes both the readers of and the authors for the journal, all those who are enthusiastic in searching the new and more effective ways of solving numerous medical problems. We hope that those who want to make their contribution to the science of medicine will find our journal helpful and encouraging. The journal is accredited by the National Council for Accreditation and Attestation. The journal publishes official papers, scientific articles, editorials, clinical studies and cases, lectures, methodological guides, reviews, brief reports, and correspondence. The journal welcomes articles in English, Romanian and Russian. The journal editorial policy provides the prompt publication of papers within 12 weeks after receiving them.De la prima apariţie în 1958, revista susţine şi dezvoltă noile idei în domeniul medicinii, în Republica Moldova. Colegiul de redacţie agrează cu multă consideraţie atât cititorii cât şi autorii articolelor, pe toţi acei care cu mult entuziasm caută noi şi mult mai efective metode de soluţionare a multiplelor probleme ale medicinii. Sperăm, că toţi acei care doresc să-şi aducă aportul la dezvoltarea ştiinţelor medicale, vor găsi revista noastră utilă şi atractivă. Revista este acreditată de către Consiliul Naţional de Acreditare şi Atestare. Revista publică comunicări oficiale şi, totodată, sunt editate diverse publicaţii, inclusiv independente: articole ştiinţifice, editoriale, cercetări şi prezentări de cazuri clinice, prelegeri, îndrumări metodice, articole de sinteză, relatări scurte, corespondenţe şi recenzii. Revista publică articole în limba engleză, română şi rusă. Politica de editare a revistei prevede examinarea operativă și publicarea articolelor timp de 12 săptămâni după înaintare.С первого дня своего выпуска в 1958 году журнал стремится поддерживать и развивать новые идеи в области медицины в Молдове. Редакционная коллегия всегда рада как читателям, так и авторам статей, всем тем, кто с энтузиазмом ищет новые, более эффективные способы решения многочисленных задач медицины. Мы надеемся, что все те, кто хотят внести свой вклад в медицинскую науку, найдут наш журнал полезным и вдохновляющим. Журнал аккредитован Высшей Аттестационной Комиссией Республики Молдова. В журнале печатаются официальные материалы, научные статьи, наблюдения из клинической практики, обобщающие статьи, краткие сообщения, методические указания, рецензии и корреспонденция. В журнале публикуются статьи на английском, румынском и русском языках. Издательская политика журнала предусматривает оперативное рассмотрение и публикацию статей в среднем в течение 12 недель после поступления

New Insight into Cerebrovascular Diseases

“Brain circulation is a true road map that consists of large extended navigation territories and a number of unimagined and undiscovered routes.” Dr. Patricia Bozzetto Ambrosi This book combines an update on the review of cerebrovascular diseases in the form of textbook chapters, which has been carefully reviewed by Dr. Patricia Bozzetto Ambrosi, Drs. Rufai Ahmad and Auwal Abdullahi and Dr. Amit Agrawal, high-performance academic editors with extensive experience in neurodisciplines, including neurology, neurosurgery, neuroscience, and neuroradiology, covering the best standards of neurological practice involving basic and clinical aspects of cerebrovascular diseases. Each topic was carefully revised and prepared using smooth, structured vocabulary, plus superb graphics and scientific illustrations. In emphasizing the most common aspects of cerebrovascular diseases: stroke burden, pathophysiology, hemodynamics, diagnosis, management, repair, and healing, the book is comprehensive but concise and should become the standard reference guide for this neurological approach

Brain and Human Body Modeling

This open access book describes modern applications of computational human modeling with specific emphasis in the areas of neurology and neuroelectromagnetics, depression and cancer treatments, radio-frequency studies and wireless communications. Special consideration is also given to the use of human modeling to the computational assessment of relevant regulatory and safety requirements. Readers working on applications that may expose human subjects to electromagnetic radiation will benefit from this book’s coverage of the latest developments in computational modelling and human phantom development to assess a given technology’s safety and efficacy in a timely manner. Describes construction and application of computational human models including anatomically detailed and subject specific models; Explains new practices in computational human modeling for neuroelectromagnetics, electromagnetic safety, and exposure evaluations; Includes a survey of modern applications for which computational human models are critical; Describes cellular-level interactions between the human body and electromagnetic fields