Download or read book Quantitative Measurements of Cerebral Hemodynamics Using Magnetic Resonance Imaging written by Amit Mehndiratta and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Brain Research written by J. P. Schadé and published by . This book was released on 1963 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MRI Methods for Cerebrovascular Hemodynamics Assessment written by Leonardo A. Rivera and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intracranial vascular hemodynamics and vascular architecture are modified in a wide array of diseases, including tumors, stroke, and varying forms of dementia. Non-invasive methods capable of quantitatively assessing cerebrovascular disease are highly desirable. Magnetic resonance imaging (MRI) enables non-invasive quantitative assessment of cerebral hemodynamics and structure. Within this framework, the work in this thesis describes and applies innovative approaches to characterize hemodynamics in the cerebral vasculature using quantitative MRI. Additionally, these methods are validated and exhibited in-vivo. To assess vascular hemodynamics in relatively large arteries and veins a 4D flow MRI approach was used. This method enables both volumetric angiographic and quantitative assessment of blood flow velocities in a single acquisition with full volumetric coverage and sub millimeter resolution. 4D flow MRI was applied to healthy and pathological populations of individuals including: healthy younger and older adults, Alzheimer's disease (AD), mild cognitively impaired (MCI) and dural arteriovenous fistula (DAVF) patients. Targeted blood flow derived measurements, such as blood flow rates, pulsatility and resistivity, area, flow directionality, and pressure gradients were quantified. To assess small vessels and brain parenchyma tissue hemodynamics T1 and T2* mapping techniques were explored using ferumoxytol enhanced MRI. In addition, time-resolved T2* ferumoxytol enhanced MRI was implemented. With these approaches small vessel pulsatility and cerebral blood volume (CBV) were successfully characterized in gray and white matter tissues in a cohort of healthy volunteers.

Download or read book Evaluation of Cerebral Hemodynamics by Quantitative Perfusion MRI written by Matthias Johannes Paulus Osch and published by . This book was released on 2002 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hemodynamic Measurements and Modeling for Functional Magnetic Resonance Imaging written by Reswanul Kabir Khan and published by . This book was released on 2014 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: In imaging, short wavelength (high-frequency) particles scattered from targets typically yield greater spatial resolutions than longer wavelengths. X-Rays, for example are typically within 2 orders of magnitude of a nanometer wavelength to achieve desired resolutions for medical imaging. Although better for imaging, this poses a health risk for subjects as ionizing radiation and this limits its use. Functional Magnetic Resonance Imaging (fMRI) avoids this issue by using radiation of much larger wavelengths, 4.8 m (62.5 MHz), that are relatively harmless. Instead of scattering, these photons are used to excite protons between spin-states in an external magnetic field. Magnetization relaxation rates and dephasing as a function of space and time are then measured to reconstruct images. This dissertation develops experimental methods to understand and interpret the biophysical underpinnings of fMRI in terms of blood flow and oxygen concentration changes. In neuroscience, fMRI may be used to deduce brain activity. Brain activity is a general term related to neuronal firing rate, which metabolizes oxygen. Deoxygenated blood increases proton spin dephasing. This is the physical mechanism that ultimately yields contrast in the fMRI signal. This is known as Blood-Oxygen Level Dependent (BOLD) contrast. A critical piece of information in this process, hemodynamics, is the dynamics of cerebral (brain) oxygen concentrations in relation to blood flow. The hemodynamics of BOLD contrast fMRI and its relation to brain activity is vital. In this dissertation, I have classified hemodynamic data as a function of space and time in cerebral cortex as well as testing a rudimentary hemodynamic model. I have taken fMRI measurements in three human subjects to identify spatial and temporal hemodynamic trends in brain. Furthermore, I've analyzed laser-speckle imaging in three subjects to identify spatiotemporal trends in blood speed. The final portion of this dissertation relates developments of a hemodynamic model of BOLD.

Download or read book MRI Based Cerebral Oxygenation Measures in Humans written by Jeffrey Neil Stout and published by . This book was released on 2018 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: MRI based cerebral oxygenation measures could enable brain-centered clinical care and improve understanding of brain energy use throughout human development. We made technical improvements to two MR oxygenation imaging techniques, and explored the concordance between various methods to quantify the cerebral metabolic rate of oxygen consumption (CMRO2 ) and other aspects of cerebral metabolism in neonates with congenital heart disease (CHD). Using a turbo gradient spin echo readout we reduced the scan time of the existing QUantitative Imaging of eXtraction of Oxygen and TIssue Consumption (QUIXOTIC) technique for measurements of global oxygen extraction fraction by eightfold while improving robustness to physiological noise and motion. We also corrected the effect of residual cerebrospinal fluid signal on transverse relaxation time quantification. The detected change in oxygen extraction fraction in the visual cortex during visual stimulation, demonstrated the technique's suitability for absolute quantitative functional MRI experiments. T2-Relaxation Under Spin Tagging (TRUST) has been used in several studies, including one with neonates, to quantify blood oxygen saturation. We investigated how involuntary subject motion affects quantification by incorporating volume navigators into TRUST to monitor motion during scans. We demonstrated that motion causes an upward bias in venous oxygen saturation quantification. Finally, we used TRUST and phase contrast MRI to measure CMRO2 in neonates with congenital heart disease (CHD) and explored the link between CMRO2 and other aspects of metabolism examined by MR spectroscopic imaging. We found a relationship between cerebral oxygenation and lactate and glutathione concentrations in white matter. We also sought to extend the reach of absolute MRI-based quantification by comparing it to bedside near infrared spectroscopy-based measurements. We found good agreement between oxygenation measurements, but no agreement between cerebral blood flow measurements, suggesting that hemodynamics vary more rapidly than oxygenation. Robust MR-based oxygenation imaging would improve clinical care and our understanding of how abnormal oxygen delivery affects brain development. Seeking a complete picture of cerebral metabolism throughout development, future work will perfect techniques to monitor cerebral hemodynamics, oxygenation and metabolism from midgestation to old age.

Download or read book Cerebral Blood Flow written by Aldo Rescigno and published by Springer. This book was released on 1988 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NATO Advanced Study Institute on "Cerebral Blood Flow: Mathematical Models, Instrumentation, and Imaging Techniques" was held in L'Aquila, Italy, June 2-13, 1986. Contributions to this program were received from the University of L'Aquila, Consiglio Nazionale delle Ricerche, Siemens Elettra S.p.A., and Bracco S.p.A. Recent studies of the cerebral blood circulation have lagged behind analysis of other parameters such as glucose utilization, transmitter distribution, and precursors. This Advanced Study Institute tried to fill this gap by analyzing in detail different physical techniques such as Autoradiography (including Double-Tracer Auto radiography and highly specific tracers as Iodoantipyrine, Micro spheres), Single Photon Emission Computed Tomography, Nuclear Magnetic Resonance. Each method was analyzed in regards to its precision, resolution, response time. A considerable part of this Institute was devoted to the mathematics of CBF measurement, in its two aspects, i.e. the modeling of the underlying kinetic system and the statistical analysis of the data. The modeling methods proposed included the development of a differential algebra whereby the differential and integral equations involved could be solved by simple algebraic methods, including graph theoretical ones; the statistical methods proposed included the illustration of different parametrizations of possible use in the interpretation of experimental results.

Download or read book Quantification of Cerebral Hemodynamics from Dynamic Susceptibility Contrast magnetic Resonance Imaging Technique written by Denis Peruzzo and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Assessment of Brain Function and Hemodynamics Using Magnetic Resonance Imaging written by Karthikeyan Kuppusamy and published by . This book was released on 1997 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Assessment of Cerebral Hemodynamics by Deconvolution with Dynamic Susceptibility Contrast magnetic Resonance Imaging written by Francesca Zanderigo and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Regional Oxygenation and Cerebral Hemodynamics Using Rapid MRI written by Bernice Erland Hoppel and published by . This book was released on 1993 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Implementation and Assessment of Novel Functional Hemodynamic MRI Measurements in the Brain for Evaluation of Disease and Treatment written by Adam Martin Winchell and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The characterization and quantification of cerebral hemodynamics can provide critical biological information of current physiology. Divergent hemodynamic processes can provide integral knowledge into different pathophysiologies and aid in the diagnosis and evaluation of treatment. A variety of different magnetic resonance (MR) imaging techniques were implemented to quantify cerebral hemodynamics in a diverse set of neurological conditions. The first study investigated the association of blood flow and blood volume of a diffuse intrinsic pontine glioma tumor by arterial spin labeling (ASL) and dynamic susceptibility weighted contrast MR as a predictive marker of survival. Higher tumor blood flow and maintenance of higher blood flow was associated with longer progression free survival. In the following study, ASL was used to evaluate the association of resting state perfusion and neurocognitive impairment in long-term survivors of pediatric acute lymphoblastic leukemia and Hodgkin lymphoma. Systematic differences in resting state perfusion and neurocognitive performance was observed between the cancer survivor groups. In the last few studies, a variety of different MR techniques were implemented to investigate the hemodynamic properties of Sickle cell disease (SCD). Susceptibility weighed imaging (SWI) was used to investigate difference in the cerebral venous vascular system integrity between SCD patients and healthy controls. A segmentation procedure was introduced to quantify the normalized visible venous volume (NVVV). The study showed that SCD effects SWI venous conspicuity by having a lower NVVV with a global isointense venous contrast. A follow-up study improved the accuracy of the NVVV quantification by removing hypointese arterial vessel contamination. This new segmentation framework combined information from SWI and MR angiography. In the final study, intracranial blood velocity measurements made by MRI and transcranial Doppler ultrasound were compared in a cohort of SCD patients. Excessive intracranial blood velocity is a clinical indicator of elevated stroke risk in SCD patients. Blood velocities correlated well between the different modalities, however, MR systematically underestimated the blood velocity. The ability to noninvasively image, quantify, and monitor biological processed represents a powerful diagnostic toolkit for physiological evaluation. Characterizing cerebral hemodynamics only represents a small but vital tool for the future of medicine.

Download or read book Cerebrovascular Reactivity written by Jean Chen and published by Humana. This book was released on 2021-11-06 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Quantitative Cerebral Blood Flow Measurements Using Stable Xenon CT written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tissue Damage Quantification in Alzheimer s Disease Brain Via Magnetic Resonance Gradient Echo Plural Contrast Imaging GEPCI written by Yue Zhao and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alzheimer's disease (AD) affected approximately 48 million people worldwide in 2015. Its devastating consequences have stimulated an intense search for AD prevention and treatment. Clinically, AD is characterized by memory deficits and progressive cognitive impairment, leading to dementia. Over the past two to three decades, researchers have found that amyloid-beta (A[beta]) plaques and neurofibrillary tau tangles occur during a long pre-symptomatic period (preclinical stage) before the onset of clinical symptoms. As a result, identification of the preclinical stage is essential for the initiation of prevention trials in asymptomatic individuals. Currently, Positron Emission Tomography (PET) imaging with injected 11C or 18F containing radiotracers (e.g., Pittsburgh compound B, PiB or florbetapir-fluorine-18, 18F-AV-45) is widely used to detect amyloid deposition in vivo and to identify this preclinical stage. However, PET scans are time consuming (about 1 hour), require injection of a radiotracer, thus, exposing the patient to ionizing radiation. After the preclinical stage, AD patients begin to show clinical symptoms, referred as a very mild or mild AD group. Post-mortem studies show that neuronal damage is the most proximate pathological substrate of cognitive impairment in AD compared with amyloid and tau deposition. Thus, a diagnostic tool is needed for detection of neuronal loss in vivo. As a faster, non-invasive, and radiation free imaging technique, Magnetic Resonance Imaging (MRI) plays an important role in the diagnosis of cognitive diseases. Conventional MRI yields superb definition of brain anatomy and structure and provide important volumetric information (e.g., brain atrophy). However, conventional MRI cannot provide microstructural and functional insight into the pathology of AD. The approach developed in Yablonskiy's lab is based on the Gradient Echo Plural Contrast Imaging (GEPCI) protocol, which provides quantitative in vivo measurements of transverse relaxation properties of the tissue water 1H spins as determined from the gradient echo MRI signal. The measurements are corrected for macroscopic magnetic field inhomogeneity effects and physiologic-motion-driven fluctuations in magnetic field as these are the major artifacts present with the gradient echo technique. The principal relaxation property used in this dissertation is the tissue-specific transverse relaxation rate constant, R2*. The R2* value reflects the microscopic and mesoscopic magnetic field inhomogeneities rising from the complex tissue-water-environment within the human brain. In turn, changes in R2* reflect changes in the tissue's microscopic and mesoscopic tissue structure. However, because of the presence of the cerebral blood vessel network, the magnetic-susceptibility-driven blood-oxygen-level dependent (BOLD) effect also makes a significant contribution to R2*. A previously developed approach, quantitative BOLD (qBOLD), allows the separation of R2* into a tissue specific R2t* without blood vessel effects and the BOLD component. Quantifying the BOLD component allows the calculation of cerebral hemodynamics parameters, such as oxygen extraction fraction (OEF) and deoxygenated cerebral blood volume (dCBV). These parameters (R2*, R2t*, OEF, dCBV) describe structural and functional properties of tissue at the microstructural level in the human brain. In the study of normal aging, quantitative GEPCI measurements showed that R2t* increases with age while hemodynamic parameters, i.e., relative OEF and dCBV remain constant in most cerebral cortical regions. The comparison between quantitative GEPCI measurements and literature information suggest that (a) age-related increases in the cortical R2t* mostly reflect the age-related increases in the cellular packing density (or neuronal density); (b) regions in a brain characterized by higher R2t* contain a higher concentration of neurons with less developed cellular processes (dendrites, spines, etc.); and (c) brain regions characterized by lower R2t* represent regions with lower concentration of neurons but more developed cellular processes. In the Alzheimer study, R2* and R2t* together demonstrated significant differences among the normal, preclinical and mild AD groups. First, the results uncovered strong correlations between R2* and A[beta] deposition measured by the PiB PET-tracer in several cortical regions (e.g., medial temporal lobe and precuneus). This finding indicates that R2* may be a potential surrogate marker for A[beta] deposition. The strongest correlation was found in the medial temporal lobe (MTL), particularly in the parahippocampal cortex, which can be used to distinguish the normal and preclinical groups. Second, R2t* in the hippocampus, which characterized the hippocampal cellular integrity demonstrated much stronger correlations with psychometric tests than volume quantification of hippocampal atrophy. Importantly, decreased R2t* characterizing cellular damage was detected even in the hippocampal areas not affected by atrophy. In addition, R2t* significantly decreased in the mild AD group but was preserved in the preclinical group compared with the normal group. These results indicate a significant cellular density decrease in the mild group but not in the preclinical group, which is consistent with previous histological studies. In summary, GEPCI provides a new approach for evaluation of AD-related tissue pathology in vivo in the preclinical and early symptomatic stages of AD. Since MRI is widely available worldwide and does not require radiation exposure, it provides the opportunity to obtain new information on the pathogenesis of AD and for pre-screening cohorts (stratification) for clinical drug trials.

Download or read book PanVascular Medicine written by Peter Lanzer and published by Springer. This book was released on 2015-03-30 with total page 5004 pages. Available in PDF, EPUB and Kindle. Book excerpt: ​Vascular management and care has become a truly multidisciplinary enterprise as the number of specialists involved in the treatment of patients with vascular diseases has steadily increased. While in the past, treatments were delivered by individual specialists, in the twenty-first century a team approach is without doubt the most effective strategy. In order to promote professional excellence in this dynamic and rapidly evolving field, a shared knowledge base and interdisciplinary standards need to be established. Pan Vascular Medicine, 2nd edition has been designed to offer such an interdisciplinary platform, providing vascular specialists with state-of-the art descriptive and procedural knowledge. Basic science, diagnostics, and therapy are all comprehensively covered. In a series of succinct, clearly written chapters, renowned specialists introduce and comment on the current international guidelines and present up-to-date reviews of all aspects of vascular care.

Download or read book Quantitative MRI of the Brain written by Mara Cercignani and published by CRC Press. This book was released on 2018-01-12 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building on the success of the first edition of this book, the winner of the 2004 British Medical Association Radiology Medical Book Competition, Quantitative MRI of the Brain: Principles of Physical Measurement gives a unique view on how to use an MRI machine in a new way. Used as a scientific instrument it can make measurements of a myriad of physical and biological quantities in the human brain and body. For each small tissue voxel, non-invasive information monitors how tissue changes with disease and responds to treatment. The book opens with a detailed exposition of the principles of good practice in quantification, including fundamental concepts, quality assurance, MR data collection and analysis and improved study statistical power through minimised instrumental variation. There follow chapters on 14 specific groups of quantities: proton density, T1, T2, T2*, diffusion, advanced diffusion, magnetisation transfer, CEST, 1H and multi-nuclear spectroscopy, DCE-MRI, quantitative fMRI, arterial spin-labelling and image analysis, and finally a chapter on the future of quantification. The physical principles behind each quantity are stated, followed by its biological significance. Practical techniques for measurement are given, along with pitfalls and examples of clinical applications. This second edition of this indispensable 'how to' manual of quantitative MR shows the MRI physicist and research clinician how to implement these techniques on an MRI scanner to understand more about the biological processes in the patient and physiological changes in healthy controls. Although focussed on the brain, most techniques are applicable to characterising tissue in the whole body. This book is essential reading for anyone who wants to use the gamut of modern quantitative MRI methods to measure the effects of disease, its progression, and its response to treatment. Features: The first edition was awarded the book prize for Radiology by the British Medical Association in 2004 Written by an authority in the field: Professor Tofts has an international reputation for quantification in MRI Gives specific ‘how to’ information for implementation of MRI measurement sequence techniques