Jeffrey J. Neil, MD, PhD - US grants

Measurement of regional perfusion is critical for the understanding of a variety of physiological and pathological processes. Availability of a technique for this measurement that is non-invasive, provides excellent spatial resolution and is suitable for repeated, serial measurements would be of considerable importance. Recent advances in NMR imaging have generated a number of possible methods for measuring cerebral perfusion, many of which fulfill some or all of these criteria. Remarkably, despite the enormous potential of these NMR techniques, none has yet been fully developed or rigorously validated in vivo against a widely-accepted measurement of regional organ perfusion. We propose to develop and validate two NMR methods of measurement of regional cerebral perfusion for potential use in humans. The first employs 2H2O as a freely-diffusible tracer and the second relies on spin-echo amplitude attenuation caused by movement of protons (1H2O) in a magnetic field gradient. The 2H2O tracer method will first be developed with single-voxel experiments in rats. The signal-to-noise and measurement-time constraints related to the use of various sites for tracer administration will be determined and evaluated with both washin and washout kinetic protocols. Rigorous validation of the measurements will be carried out by concomitant measurements employing the radiolabeled microsphere technique. In order to develop the 1H spin-echo technique for quantitative, single- voxel perfusion measurements in rat, a high-performance, linear z-axis gradient and compatible homogeneous-excitation, surface-coil-receive probe will be constructed. The assumptions underlying the method will be limitations of the techniques. It will then be validated against concomitant flow measurement in rat by the radiolabeled microsphere technique. Both techniques will then be extended to multi-voxel experiments (perfusion imaging) in cats with development of the necessary probe and gradient hardware for interrogation of cat brain. The limitations for measurement time, spatial resolution and precision will be determined. Again, measurements made with both methods will be compared with concomitant measurements by the radiolabeled microsphere technique. In the final phase, a sufficient number of studies will be performed on monkeys, whose size is similar to that of human neonates, to further assess the suitability of these techniques for use in humans.

DESCRIPTION: (Applicant's Description) The International Society for Magnetic Resonance in Medicine (ISMRM), created from the merger of the Society of Magnetic Resonance in Medicine and The Society for Magnetic Resonance Imaging, is the only international non-profit professional association devoted to the promotion of research and education in all applications of magnetic resonance in medicine, biology, and related fields. Members include clinicians, physicists, engineers, biochemists, chemists, and technologists. The ISMRM is, at present, the only society that combines both basic and applied disciplines, including clinical research, to best serve medicine and science. This merged society was founded in 1994 and has now reached a membership of over four thousand. Scientific meetings are held annually with every third year's meeting located outside of North America. In 1997, the Fifth Annual Meeting of the Society will be held in Vancouver, British Columbia from April 12-18th. An attendance of over four thousand scientists, physicians and students is anticipated. This proposal requests funds to support, in-part, educational stipends for meritorious students and postdoctoral trainees from the U.S. whose abstracts are submitted and accepted through the regular peer review process of the Society. The amount of each award will be 70 percent of the anticipated travel cost for a particular student, with the remaining 30 percent being provided by the student's supervisor. The Society has earmarked an amount of $125,000, derived from unrestricted corporate donations, for the support of this program. Of this amount, fifty-eight percent, or $72,500, has be reserved for students from the U.S. This amount is sufficient for 74 awards, but we anticipate that 104 young investigators from the U.S. will qualify for awards. This proposal requests supplemental funds in the amount of $29,295 from NIH to allow 30 additional awards. In the context of limited funding from peer reviewed, industrial and clinical revenue sources faced by many research laboratories, the requested support has become critical to stipulate young investigators to actively contribute their research and help bring together established researchers and students in this rapidly evolving field of medical research. Of the 223 students who qualified for travel stipends for the previous meeting of ISMRM, we were able to fund only 180 or 81 percent. The support requested herein is vital to our efforts to support as many students as possible for the upcoming meeting.

DESCRIPTION (Adapted from Applicant's Abstract): Diffusion-weighted imaging (DWI) is a magnetic resonance imaging method that shows great promise for early detection of a number of forms of central nervous system (CNS) injury, including stroke, trauma, and status epilepticus. At the present time, the mechanism(s) underlying the rapid change in contrast in diffusion-weighted images after CNS injury is poorly understood. As a first step to understanding these mechanisms, two classes of experiments are proposed to evaluate changes in water apparent diffusion coefficient (ADC) in the intra-and extracellular spaces in association with rat models of stroke or status epilepticus. The first utilizes NMR-detectable, compartment-specific probes to indirectly detect changes in motion in either the intra- or extracellular space in association with CNS injury. Probes of the intracellular space will be 133Cs+, in situ generated 2-fluorodeoxyglucose-6-phosphate (with 19F detection), 23Na+, and endogenous 1H metabolites. Probes of the extracellular space will be 3-aminopropylphosphonate (with 31P detection), 2-fluorodeoxyglucose-6-phosphate (with 19F detection), and 23Na+. The second class of experiments will involve infusion of relaxation contrast agent (gadoteridol) into the lateral cerebral ventricle of rats, from which it spreads throughout the extracellular space and greatly reduces the T1 relaxation time constant of extracellular water. Once this is accomplished, it is possible to design NMR pulse sequences which permit acquisition of ADC data which is heavily weighted to signal from either intra- or extracellular compartment. For these studies, compartment-specific changes in water ADC will be correlated with histologic assessment of infarct severity. In a third class of experiments, the possibility that some of the ADC decrease associated with stroke is due to underestimates of ADC caused by paramagnetic effects of deoxyhemoglobin will be examined. Taken together, these studies are designed to begin unraveling the compartment-specific ADC changes responsible for DWI contrast in an effort to permit more precise use of this promising imaging modality.

DESCRIPTION (provided by applicant): Neonatal brain injury remains a major cause of morbidity and mortality for premature infants, with up to 50% of infants having cognitive and/or behavioral problems by school age. While many studies have focused on white matter abnormalities as the cause of this dysfunction, there is mounting evidence that premature infants also sustain significant injury to cerebral cortical grey matter. We propose to develop and apply MR diffusion methods to evaluate cortical organization. The methods to be used are based on high-angular resolution diffusion imaging (HARD) and q-space diffusion imaging (QSI). Both methods permit detailed, three-dimensional assessments of water displacement. QSI requires more extensive data acquisition than HARD. As a result, HARD data acquisition schemes are more amenable to use in human subjects. HARD data will be analyzed via spherical harmonic decomposition. QSI data will be analyzed via generation of probability density functions by three-dimensional Fourier transformation. The proposed studies are divided into two general categories. The first involves evaluation of fixed human autopsy tissue. Both QSI and HARD data will be obtained to determine the relationship between HARD and QSI anisotropy measures as well as suggest optimum data acquisition parameters for study of live infants. They will also be used to delineate the progression of diffusion anisotropy parameters during cortical maturation. The second category is the acquisition of HARD data from live infants. This will entail optimization of HARD data acquisition parameters. In addition, anisotropy values from occipital cortex will be compared between normal, term control infants and preterm infants at term-equivalent. This will provide information regarding the effects of prematurity on cortical development. Anisotropy values will also be compared between premature infants at term-equivalent with and without white matter injury to evaluate associations between white matter injury and cortical disruption. If successful, these methods will provide a potential means of identifying the nature and extent of cortical injury in premature infants. They may also allow identification of infants at risk for subsequent neurodevelopmental disability at the time the infants are discharged from the hospital.

nerve injury; method development; magnetic resonance imaging; diagnosis design /evaluation; brain imaging /visualization /scanning; brain disorder diagnosis; central nervous system; disease /disorder model; cerebral ischemia /hypoxia; intracellular; cerebral ventricles; generalized seizures; brain injury; extracellular matrix; cell water; stroke; early diagnosis; bioimaging /biomedical imaging; laboratory rat; injection /infusion; radiofluorescent probe;

Despite many speculative papers on the topics of brain morphogenesis, particularly cortical folding, the biomechanical factors that are responsible for normal and abnormal brain development are largely unknown. The general objective of this research is to develop quantitative biomechanical models for brain morphogenesis. The mathematical models will be based on fundamental mechanical principles and state-of-the-art experimental measurements of structure, microstructure, and mechanical properties, combined with precise, quantitative descriptions of growth and remodeling. In conjunction with experiments, these models will be used to test the hypothesis that spatial and temporal variations in mechanical stress, viscoelastic properties, and growth of the developing brain produce observed changes in shape. This project focuses on two specific periods of brain development where dramatic changes in form are apparent: (1) the early period of expansion and differentiation of the neural tube into the primary vesicles of the brain (forebrain, midbrain, and hindbrain); and (2) the later period of folding of the cerebral cortex (gyrogenesis). Mathematical and computational modeling of the nonlinear, three-dimensional continuum mechanics of brain formation is a necessary complement to classical biological approaches to this basic problem in neurobiology. The results from this project will provide fundamental new insight into the biomechanical mechanisms of brain development.

In this project, mathematical models for growth and development of the brain will be built and tested. The brain's form is closely related to its function, but the mechanisms that drive the brain into its final shape are poorly understood. The project focuses on two stages that appear particularly important: (1) the stage of early development when three primary segments of the brain emerge; (2) the stage of later development when the outer surface of the brain folds into a convoluted pattern. Many educated guesses about the process of brain development have been proposed, but none have been supported by convincing evidence. Hypothesized mechanisms will be described in quantitative, precise, computer simulations, and the results will be assessed objectively. New experimental studies will provide physical parameters for these computer models. The objective is a coherent, physically plausible, understanding of the form-function relationship that drives brain development. This information is of fundamental importance to understanding the normal brain. In addition, many disabilities and diseases of the brain, such as schizophrenia, epilepsy, and mental retardation are associated with abnormal brain shape. This project will address important gaps in the fundamental knowledge of brain development needed to address these problems.

DESCRIPTION (provided by applicant): This is the renewal application of the Neurological Sciences Academic Development Award (NSADA) that has supported six trainees in pediatric neurology at Washington University over the past decade. The new application reflects the growth and changes in pediatric neurology over the last decade and includes mentors with research and clinical expertise in academic areas that have direct impact on modern pediatric neurology: developmental neuroscience, cognitive neuroscience, neuronal injury, and epilepsy. Several mentors have overlapping areas of interest. The proposed mentors come from within the Department of Neurology, as well as the Departments of Anatomy & Neurobiology, Genetics Psychiatry, Molecular Biology & Pharmacology, and Neurological Surgery. The program will be specifically tailored for the four trainees and depend heavily upon their prior research experience and career preferences. Trainees who enter the program with extensive research experience will be encouraged to replenish their fund of knowledge and then embark upon new research with the guidance of the Program Director and an Executive Committee. Less experienced trainees may spend up to a year in formal course work in the Neuroscience Program of the Division of Biology and Biomedical Sciences of Washington University. In either case, trainees will be able to draw on the resources of 23 mentor faculty committed to this application and a wider neuroscience community comprised of more than 120 faculty engaged in active research. While trainees will be expected to receive most of their supervision from their specific mentors, there is enormous interaction between the senior mentors and their respective laboratories, so trainees will have abundant opportunities for contact with experienced researchers. Graduates of NSADA training should be competitive for independent funding after completion of three years.

DESCRIPTION (provided by applicant): Preterm birth is a major public-health issue because of its increasing incidence combined with the frequent occurrence of subsequent behavioral, neurological, and psychiatric challenges faced by surviving infants. Approximately 10-15% of very preterm children (born <30 weeks gestational age) develop cerebral palsy, and 30 - 60% of very preterm children experience cognitive impairments. These impairments include visual-motor problems, attentional difficulties, impaired memory, delayed acquisition of language, executive dysfunction, learning disabilities, poor social skills, and higher rates of social withdrawal, anxiety and depression. In addition, an increased prevalence of developmental disorders such as attention deficit/hyperactivity disorder, autism and schizophrenia, has been described in the preterm population. These adverse outcomes are related to white matter (WM) and grey matter (GM) injury sustained during the neonatal period and its effects on subsequent brain development. We seek to develop imaging biomarkers, measurable during infancy, that provide sensitivity and specificity in identifying infants at risk for poor neurodevelopmental outcome. The biomarkers will consist of the following magnetic resonance (MR) imaging measures: 1) conventional T1- and T2-weighted images, 2) volumetry (volumes for cortical GM, deep nuclear GM, myelinated WM, unmyelinated WM, and cerebrospinal fluid), 3) diffusion tensor imaging (apparent diffusion coefficient, relative anisotropy, axial and radial diffusivity), and 4) surface-based morphometry (integrated folding index, average sulcal depth, cortical surface area, percentage of buried cortex). The main cohort of this study will consist of 120 very preterm infants born <30 weeks gestational age. They will undergo MR studies soon after birth, at 30 weeks postmenstrual age (PMA), 34 weeks PMA, and term equivalent. Infants enrolled during Year 1 (n = 30) will also be imaged at age 4 years. The MR indices listed above will be compared with MR data from healthy control subjects and clinical outcome data obtained at term equivalent and 2 and 4 years of age. The proposed studies are designed to engender a deeper understanding of the nature and timing of cerebral injury, laying the groundwork for the development of neuroprotective strategies and improving clinical practices. The longitudinal design will allow us to study both structural abnormalities and compensatory changes in response to injury. Identification during the newborn period of infants at high risk for poor developmental outcome will allow early targeting of therapy services to these infants. If successful, the proposed studies will lead to improved outcomes for prematurely-born infants. Project Narrative: This study is designed to use magnetic resonance imaging to improve our understanding of the brain injury sustained by prematurely-born infants. This understanding has the potential to improve clinical practices and assist with the development of medications to reduce injury in these babies, ultimately reducing disabilities. It will also help identify those infants who are at high risk for developing cerebral palsy or mental retardation so they can be provided early access to therapy services.

The Imaging Core is designed to support high quality basic and applied magnetic resonance (MR) imaging research relevant to understanding and preventing the causes of intellectual and developmental disabilities. To accomplish this mission, the core will provide service with two objectives. The first is to foster translational research by enriching interdisciplinary collaboration across basic and clinical sciences using imaging as a bridging research tool. The second is to provide cost-effective, scientifically robust, state-of-theart core services and facilities to maximize the quality and impact of the science produced by center investigators and their collaborators. The scientific leadership of the Imaging Core will be actively integrated with that of both the human and animal model clinical cores to optimize the application of imaging as a translational tool for center investigators and their collaborators. The Imaging Core will include resources and personnel related to several MR imaging approaches applicable to both human and animal studies. The modalities available will include: [unreadable] Conventional imaging including post-acquisition analysis of volumetry and cartography [unreadable] Diffusion tensor imaging [unreadable] Functional MRI and functional connectivity MRI This proposal builds on existing strengths at Washington University. These strengths include: 1)outstanding physical resources that will be fully optimized for the evaluation of children with developmental disabilities;2) remarkable intellectual resources with expertise in MR imaging and spectroscopy of both human and animal subjects;3) considerable experience in obtaining MR studies of infants and children without sedation;and 4) a diverse, high-quality base of NIH-funded investigators engaged in clinical and translational studies of developmental disabilities that would benefit from this core.