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There are lots of dynamic process exist co-currently and spontaneously when the neurons in the brain are activated by the external stimulation, like cerebral blood flow (CBF) change, oxygen extraction change. The study of the dynamic relationship among these physiological variables, which describe the brain activity through different aspects, can help people understand the brain function when it gets excited and researchers can interpret the physiological meaning of these parameters better. The most common functional magnetic resonance imaging techniques are BOLD and ASL fMRI, in this research, the correlation between these two methods has been studied through a simultaneous data acquisition strategy. Assessing such correlation between BOLD fMRI measures and CBF offers a link of these two to the underlying of the spontaneous brain activities. In the study, an ASL pulse sequence PICORE has been used to perform the fMRI experiment on 7 health subjects. A rapid median nerve electrical stimulation paradigm has been used to detect the activation of the brain from seven normal health right-handed human subjects. Three ROIs (SMA, S1, M1) have been selected and the data were analyzed to investigate the correlation between CBF value and BOLD signal change during brain activities. We found the CBF value rises for 5 - 6 ml/min/100g for fixed ROI and 11 - 12 ml/min/100g for non-fixed ROI and the BOLD signal change was around 0.8% for both situations. Our results shows for a fixed size ROI of each individual subject, no significant difference has been found for CBF value difference and the BOLD signal change between different runs and neither did the ratio of these two parameters (p > 0.05). When studied the activation area size for each run, we found significant difference for both CBF value difference and BOLD signal change (p
Functional Magnetic Resonance Imaging (fMRI) has become a standard tool for mapping the working brain's activation patterns, both in health and in disease. It is an interdisciplinary field and crosses the borders of neuroscience, psychology, psychiatry, radiology, mathematics, physics and engineering. Developments in techniques, procedures and our understanding of this field are expanding rapidly. In this second edition of Introduction to Functional Magnetic Resonance Imaging, Richard Buxton – a leading authority on fMRI – provides an invaluable guide to how fMRI works, from introducing the basic ideas and principles to the underlying physics and physiology. He covers the relationship between fMRI and other imaging techniques and includes a guide to the statistical analysis of fMRI data. This book will be useful both to the experienced radiographer, and the clinician or researcher with no previous knowledge of the technology.
This volume provides a comprehensive overview of the methodology, physiology, and contemporary and novel applications of cerebrovascular reactivity (CVR) measurements. The chapters in this book cover topics such as an introduction of the neurophysiology, neuroimaging, and clinical methods for CVR measurement; the use of CVR methods in the study of aging, cerebrovascular dysfunction, dementia, and brain tumors; and recommendations for measurement protocols and future applications in clinical translation. In Neuromethods series style, chapters include the kind of detail and key advice from the specialists needed to get successful results in your research center and clinical investigation. Thorough and comprehensive, Cerebrovascular Reactivity: Methodological Advances and Clinical Applications is a valuable tool that provides researchers in neuroscience and neurology with the latest resources on the measurement, interpretation, and application of CVR measurement.
Cerebral blood flow (CBF) plays a central role in the blood oxygen level dependent (BOLD) signal measured by functional magnetic resonance imaging (fMRI). Yet, age-related changes in CBF and its relationship with the BOLD response have not been studied extensively in typically developing children. Historically, positron emission tomography (PET) and single photon emission computed tomography (SPECT) have been used to study CBF during development. PET and SPECT studies have found that CBF increases rapidly in the first years of life, is elevated in childhood, and declines to adult levels in adolescence. However, due to their invasiveness, PET and SPECT studies have been limited to clinical contexts and measurements of CBF either at rest or with sedation. In addition to developmental change in CBF, studies of exercise and brain function with children (cognitive, electrophysiological, and fMRI experiments) suggest that level of physical activity affects CBF. The primary aims of this thesis were to assess whether there are age-related changes in CBF and BOLD hemodynamics during a functional task and whether there is a relationship between participants' level of physical activity and CBF measurements. To do so, this project used a noninvasive MRI method, arterial spin labeling (ASL), to examine CBF during rest and functional activity in typically developing children. Further, this study used an ASL technique, Quantitative Imaging of Perfusion using a Single Subtraction (QUIPSS), which simultaneously collects CBF and BOLD-weighted images to directly examine the relationship between CBF and the BOLD response. Participants included 8-year-old children (n = 8), 12-year-old children (n = 10), and adults 22-28 years of age (n = 9). This experiment focused on CBF in the motor cortex where stimulation with a finger tapping task was predicted to elicit a robust CBF and BOLD response. CBF was measured during a resting state scan. From functional images acquired during the task, three measurements were derived: absolute CBF change, percent CBF change, and percent BOLD change. These measures were calculated as the absolute or percent change in signal between rest and peak activity. In addition, both participant and parent reports of participants' physical activities six months prior to the scan were retrospectively obtained with a survey. Age group comparisons of the hemodynamic measures showed that 8-year-old children and 12-year-old children had significantly greater resting CBF levels than adults. There were no significant differences in resting CBF levels between 8-year-old children and 12-year-old children. Eight year olds had significantly greater absolute CBF change than adults. No significant age-related differences were observed for percent CBF and BOLD signal change. Analyses of the relationship between physical activity level and CBF showed that neither participant-reported nor parent-reported amounts of activity were related to the hemodynamic measures. This result may be due to higher than expected activity levels across the sample. Lastly, the finding that CBF is higher in children compared to adults without a corresponding elevation in BOLD signal suggests that additional physiological mechanisms that are elevated in childhood may offset the high CBF and result in a stable BOLD effect.
One of the major challenges in science is to study and understand the human brain. Numerous methods examining different aspects of brain functions have been developed and employed. To study systemic interactions brain networks in vivo, non-invasive methods such as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have been used with great success. However, each of these methods can map only certain, quite selective aspects of brain function while missing others; and the inferences on neuronal processes and information flow are often rather indirect. To overcome these shortcomings of single methods, researchers have attempted to combine methods in order to make optimal use of their advantages while compensating their disadvantages. Hence, it is not surprising that soon after the introduction of fMRI as a neuroimaging method the possibilities of combinations with EEG have been explored.This book is intended to aid researchers who plan to set up a simultaneous EEG-fMRI laboratory and those who are interested in integrating electrophysiological and hemodynamic data. As will be obvious from the different chapters, this is a dynamically developing field in which several approaches are being tested, validated and compared. Currently, there is no one best solution for all problems available, but many promising techniques are emerging. This book shall give a comprehensive overview of these techniques. In addition, it points to open questions and directions for future research.
Every few years a dissertation comes to the area of clinical application of medical technology which carries us forward as on a magic carpet into new regions of understanding and patient care. This book is such a magic carpet. It brings together, in a clear and incisive fashion, important hemodynamic principles with a simple noninvasive method of application to a part of the cerebral vasculature which has been relatively inaccessible. To the lucky and perceptive person who reads this book, a feeling of excitement and hope for progress is engendered. The diligent application of the potentials of transcranial Doppler ultrasound brings new power to our efforts in understanding the cerebral circulation and the causes, treatment and prevention of cerebrovascular disorders. Merrill P. Spencer, M. D. Director Institute of Applied Physiology and Medicine Seattle, Wash. , July 1986 Acknowledgements I am greatly indebted to Prof. He1ge Nornes, Oslo, who introduced me to the fascinating study of cerebral hemodynamics in the early 1970's and since then continually encouraged my interest in this field. It was through his pioneering work on the cerebral circulation-using peroperative electromagnetic flowmetry and Doppler techniques-that the basis was laid for the noninvasive trans cranial approach to the circle of Willis described in this book. I also gratefully acknowledge the stimulating case discussions with Prof. Peter Huber, Berne, at the very early introduction of trans cranial Doppler, the inspiring exchange of ideas with Dr. Merrill P.
Topic Editor Prof. James Duffin contributed to the development of an automated end-tidal targeting device, RespirActTM and is employed by Thornhill Medical Inc. (Toronto, Canada). RespirActTM is currently a non-commercial research tool assembled and made available by TMI to research institutions to enable CVR studies. All other Topic Editors declare no competing interests with regards to the Research Topic subject.
In the medical imaging field, clinicians and researchers are increasingly moving from the qualitative assessment of printed images to the quantitative evaluation of digital images since the quantitative techniques often improve diagnostic accuracy and complement clinical assessments by providing objective criteria. Despite this growing interest, the field lacks a comprehensive body of knowledge. Filling the need for a complete manual on these novel techniques, Quantifying Morphology and Physiology of the Human Body Using MRI presents a wide range of quantitative MRI techniques to study the morphology and physiology of the whole body, from the brain to musculoskeletal systems. Illustrating the growing importance of quantitative MRI, the book delivers an indispensable reference for readers who would like to explore in vivo MRI techniques to quantify changes in the morphology and physiology of tissues caused by various disease mechanisms. With internationally renowned experts sharing their insight on the latest developments, the book goes beyond conventional MRI contrast mechanisms to include new techniques that measure electromagnetic and mechanical properties of tissues. Each chapter offers comprehensive information on data acquisition, processing, and analysis techniques as well as clinical applications. The text organizes the techniques based on their primary use either in the brain or the body. Some of the techniques, such as diffusion-weighted imaging and diffusion tensor imaging, span several application areas, including brain imaging, cancer imaging, and musculoskeletal imaging. The book also covers up-and-coming quantitative techniques that explore tissue properties other than the presence of protons (or other MRI-observable nuclei) and their interactions with their environment. These novel techniques provide unique information about the electromagnetic and mechanical properties of tissues and introduce new frontiers of study into disease mechanisms.
This e-book will review special features of the cerebral circulation and how they contribute to the physiology of the brain. It describes structural and functional properties of the cerebral circulation that are unique to the brain, an organ with high metabolic demands and the need for tight water and ion homeostasis. Autoregulation is pronounced in the brain, with myogenic, metabolic and neurogenic mechanisms contributing to maintain relatively constant blood flow during both increases and decreases in pressure. In addition, unlike peripheral organs where the majority of vascular resistance resides in small arteries and arterioles, large extracranial and intracranial arteries contribute significantly to vascular resistance in the brain. The prominent role of large arteries in cerebrovascular resistance helps maintain blood flow and protect downstream vessels during changes in perfusion pressure. The cerebral endothelium is also unique in that its barrier properties are in some way more like epithelium than endothelium in the periphery. The cerebral endothelium, known as the blood-brain barrier, has specialized tight junctions that do not allow ions to pass freely and has very low hydraulic conductivity and transcellular transport. This special configuration modifies Starling's forces in the brain microcirculation such that ions retained in the vascular lumen oppose water movement due to hydrostatic pressure. Tight water regulation is necessary in the brain because it has limited capacity for expansion within the skull. Increased intracranial pressure due to vasogenic edema can cause severe neurologic complications and death.