Diffusion tensor imaging of rat spinal cord in vivo

Magnetic resonance imaging, with its exquisite soft tissue contrast, is an ideal modality for investigating spinal cord pathology. While conventional MRI techniques are very sensitive for spinal cord pathology, their specificity is somewhat limited. Diffusion MRI is an advanced technique which is a very sensitive and specific indicator of the integrity of white matter tracts. Diffusion imaging has been shown to detect early ischemic changes in white matter, while conventional imaging demonstrates no change. By acquiring the complete apparent diffusion tensor (ADT), tissue diffusion properties can be expressed in terms of quantitative and rotationally invariant parameters. ^ Systematic study of SCI in vivo requires controlled animal models such as the popular rat model. To date, studies of spinal cord using ADT imaging have been performed exclusively in fixed, excised spinal cords, introducing inevitable artifacts and losing the benefits of MRI's noninvasive nature. In vivo imaging reflects the actual in vivo tissue properties, and allows each animal to be imaged at multiple time points, greatly reducing the number of animals required to achieve statistical significance. Because the spinal cord is very small, the available signal-to-noise ratio (SNR) is very low. Prior spin-echo based ADT studies of rat spinal cord have relied on high magnetic field strengths and long imaging times—on the order of 10 hours—for adequate SNR. Such long imaging times are incompatible with in vivo imaging, and are not relevant for imaging the early phases following SCI. Echo planar imaging (EPI) is one of the fastest imaging methods, and is popular for diffusion imaging. However, EPI further lowers the image SNR, and is very sensitive to small imperfections in the magnetic field, such as those introduced by the bony spine. Additionally, The small field-of-view (FOV) needed for spinal cord imaging requires large imaging gradients which generate EPI artifacts. The addition of diffusion gradients introduces yet further artifacts. ^ This work develops a method for rapid EPI-based in vivo diffusion imaging of rat spinal cord. The method involves improving the SNR using an implantable coil; reducing magnetic field inhomogeneities by means of an autoshim, and correcting EPI artifacts by post-processing. New EPI artifacts due to diffusion gradients described, and post-processing correction techniques are developed. ^ These techniques were used to obtain rotationally invariant diffusion parameters from 9 animals in vivo, and were validated using the gold-standard, but slow, spinecho based diffusion sequence. These are the first reported measurements of the ADT in spinal cord in vivo . ^ Many of the techniques described are equally applicable toward imaging of human spinal cord. We anticipate that these techniques will aid in evaluating and optimizing potential therapies, and will lead to improved patient care. ^

In vivo longitudinal studies of spinal cord injury and vascular endothelial growth factor treatment

Approximately 12,000 new cases of spinal cord injury (SCI) are added each year to the estimated 259,000 Americans living with SCI. The majority of these patients return to society, their lives forever changed by permanent loss of sensory and motor function. While there are no FDA approved drugs for the treatment of SCI or a universally accepted standard therapy, the current though controversial treatment includes the delivery of high dosages of the corticosteroid methyliprednisolone sodium succinate, surgical interventions to stabilize the spinal column, and physical rehabilitation. It is therefore critically important to fully understand the pathology of injury and determine novel courses and rationally-based therapies for SCI. ^ Vascular endothelial growth factor (VEGF) is an attractive target for treating central nervous system (CNS) injury and disease because it has been shown to influence angiogenesis and neuroprotection. Preliminary studies have indicated that increased vasculature may be associated with functional recovery; therefore exogenous delivery of a pro-angiogenic growth factor such as VEGF may improve neurobehavioral outcome. In addition, VEGF may provide protection from secondary injury and result in increased survival and axonal sprouting. ^ In these studies, SCI rats received acute intraspinal injections of VEGF, the antibody to VEGF, or vehicle control. The effect of these various agents was investigated using longitudinalmulti-modal magnetic resonance imaging (MRI), neuro- and sensory behavioral assays, and end point immunohistochemistry. We found that rats that received VEGF after SCI had increased tissue sparing and improved white matter integrity at the earlier time points as shown by advanced magnetic resonance imaging (MRI) techniques. However, these favorable effects of VEGF were not maintained, suggesting that additional treatments with VEGF at multiple time points may be more beneficial, Histological examinations revealed that VEGF treatment may result in increased oligodendrogenesis and therefore may eventually lead to remyelination and improved functional outcome. ^ On the neurobehavioral studies, treatments with VEGF and Anti-VEGF did not significantly affect performance on tests of open-field locomotion, grid walk, inclined plane, or rearing. However, VEGF treatment resulted in significantly increased incidence of chronic neuropathic pain. This phenomenon could possibly be attributed to the fact that VEGF treatment may promote axonal sprouting and also results in tissue sparing, thereby providing a substrate for the growth of new axons. New connections made by these sprouting axons may involve components of pathways involved in the transmission of pain and therefore result in increased pain in those animals. ^

An exploratory analysis of variance and volatility in epileptic electroencephalograms

The electroencephalogram (EEG) is a physiological time series that measures electrical activity at different locations in the brain, and plays an important role in epilepsy research. Exploring the variance and/or volatility may yield insights for seizure prediction, seizure detection and seizure propagation/dynamics.^ Maximal Overlap Discrete Wavelet Transforms (MODWTs) and ARMA-GARCH models were used to determine variance and volatility characteristics of 66 channels for different states of an epileptic EEG – sleep, awake, sleep-to-awake and seizure. The wavelet variances, changes in wavelet variances and volatility half-lives for the four states were compared for possible differences between seizure and non-seizure channels.^ The half-lives of two of the three seizure channels were found to be shorter than all of the non-seizure channels, based on 95% CIs for the pre-seizure and awake signals. No discernible patterns were found the wavelet variances of the change points for the different signals. ^

Family Preservation Research: Where We've Been, Where We Should Be Going

Although the literature has provided many critiques of research done on family preservation programs, these critiques have usually been limited to the studies ' assumptions, approach, or methodology. Because of the nature of these critiques, suggestions for future research in this field of practice have been scattered throughout the literature and have not benefitted from a wider historical perspective. This paper examines the historical evolution of family preservation studies in child welfare and suggests future directions for research in the field. Among the suggestions the authors posit are (1) research questions should be framed by what we know about improvements in the lives of families and children served by family preservation programs; (2) future explorations should include areas that have received relatively little attention in current research, including the impact of organizational conditions on service fidelity and worker performance; (3) newer treatment models, particularly those that provide both intensive services during a crisis period and less intensive services for maintenance, should be tested; (4) data collection points in longitudinal studies should be guided by theory, and measures should change over time to reflect the theoretically expected changes in families; (5) complex measures of placement prevention and other measures that capture changes in family functioning, child well-being, and child safety, should be utilized to obtain a full picture of program effects; and (6) multiple informants should be used to provide data about program effectiveness. In addition, the authors will argue that the field should carefully consider the amount of change that should be expected from the service models delivered.

Family Preservation Services to At-Risk Families: A Macro Case Study

Although the literature has provided many critiques of research done on family preservation programs, these critiques have usually been limited to the studies ' assumptions, approach, or methodology. Because of the nature of these critiques, suggestions for future research in this field of practice have been scattered throughout the literature and have not benefited from a wider historical perspective. This paper examines the historical evolution of family preservation studies in child welfare and suggests future directions for research in the field. Among the suggestions the authors posit are (1) research questions should be framed by what we know about improvements in the lives of families and children served by family preservation programs; (2) future explorations should include areas that have received relatively little attention in current research, including the impact of organizational conditions on service fidelity and worker performance; (3) newer treatment models, particularly those that provide both intensive services during a crisis period and less intensive services for maintenance, should be tested; (4) data collection points in longitudinal studies should be guided by theory, and measures should change over time to reflect the theoretically expected changes in families; (5) complex measures of placement prevention and other measures that capture changes in family functioning, child well-being, and child safety, should be utilized to obtain a full picture of program effects; and (6) multiple informants should be used to provide data about program effectiveness. In addition, the authors will argue that the field should carefully consider the amount of change that should be expected from the service models delivered.

Multiple retinal detachment surgery: A functional outcome study. The Houston Vision Assessment Test-Retina (HVAT-Retina)

Retinal detachment is a common ophthalmologic procedure, and outcome is typically measured by a single factor-improvement in visual acuity. Health related functional outcome testing, which quantifies patient's self-reported perception of impairment, can be integrated with objective clinical findings. Based on the patient's self-assessed lifestyle impairment, the physician and patient together can make an informed decision on the treatment that is most likely to benefit the patient. ^ A functional outcome test (the Houston Vision Assessment Test-Retina; HVAT-Retina) was developed and validated in patients with multiple retinal detachments in the same eye. The HVAT-Retina divides an estimated total impairment into subcomponents: contribution of visual disability (potentially correctable by retinal detachment surgery) and nonvisual physical disabilities (co-morbidities not affected by retinal detachment surgery. ^ Seventy-six patients participated in this prospective multicenter study. Seven patients were excluded from the analysis because they were not certain of their answers. Cronbach's alpha coefficient was 0.91 for presurgery HVAT-Retina and 0.94 post-surgery. The item-to-total correlation ranged from 0.50 to 0.88. Visual impairment score improved by 9 points from pre-surgery (p = 0.0003). Physical impairment score also improved from pre-surgery (p = 0.0002). ^ In conclusion, the results of this study demonstrate that the instrument is reliable and valid in patients presenting with recurrent retinal detachments. The HVAT-Retina is a simple instrument and does not burden the patient or the health professional in terms of time or cost. It may be self-administrated, not requiring an interviewer. Because the HVAT-Retina was designed to demonstrate outcomes perceivable by the patient, it has the potential to guide the decision making process between patient and physician. ^

Systematic review of worksite-based behavior change programs that target metabolic syndrome risk factors

Approximately one-third of US adults have metabolic syndrome, the clustering of cardiovascular risk factors that include hypertension, abdominal adiposity, elevated fasting glucose, low high-density lipoprotein (HDL)-cholesterol and elevated triglyceride levels. While the definition of metabolic syndrome continues to be much debated among leading health research organizations, the fact is that individuals with metabolic syndrome have an increased risk of developing cardiovascular disease and/or type 2 diabetes. A recent report by the Henry J. Kaiser Family Foundation found that the US spent $2.2 trillion (16.2% of the Gross Domestic Product) on healthcare in 2007 and cited that among other factors, chronic diseases, including type 2 diabetes and cardiovascular disease, are large contributors to this growing national expenditure. Bearing a substantial portion of this cost are employers, the leading providers of health insurance. In lieu of this, many employers have begun implementing health promotion efforts to counteract these rising costs. However, evidence-based practices, uniform guidelines and policy do not exist for this setting in regard to the prevention of metabolic syndrome risk factors as defined by the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III). Therefore, the aim of this review was to determine the effects of worksite-based behavior change programs on reducing the risk factors for metabolic syndrome in adults. Using relevant search terms, OVID MEDLINE was used to search the peer-reviewed literature published since 1998, resulting in 23 articles meeting the inclusion criteria for the review. The American Dietetic Association's Evidence Analysis Process was used to abstract data from selected articles, assess the quality of each study, compile the evidence, develop a summarized conclusion, and assign a grade based upon the strength of supporting evidence. The results revealed that participating in a worksite-based behavior change program may be associated in one or more improved metabolic syndrome risk factors. Programs that delivered a higher dose (>22 hours), in a shorter duration (<2 years) using two or more behavior-change strategies were associated with more metabolic risk factors being positively impacted. A Conclusion Grade of III was obtained for the evidence, indicating that studies were of weak design or results were inconclusive due to inadequate sample sizes, bias and lack of generalizability. These results provide some support for the continued use of worksite-based health promotion and further research is needed to determine if multi-strategy, intense behavior change programs targeting multiple risk factors are able to sustain health improvements in the long-term.^

Change in permeation rates of acids and bases through limited use protective fabrics after repeated wash cycles

The primary objective of this study was to determine if there is a change in permeation rates when limited use protective fabrics undergo repeated exposure and wash cycles. The null hypothesis of this study was that no substantial change in permeation takes place after the test material is subjected to repeated contact with a strong acid or base and has undergone repeated wash cycles. ^ The materials tested were DuPont Tychem® CPF 3 and CPF 4 fabrics. The challenge chemicals in this study were ninety-eight percent sulfuric acid and fifty percent sodium hydroxide. Permeation testing was conducted utilizing ASTM designation F739-99a Standard Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids or Gases Under Conditions of Continuous Contact. ^ In this study, no change in permeation rates of either challenge chemical was detected for CPF 3 or CPF 4 limited use protective fabrics after repeated exposure and wash cycles. Certain unexposed areas of the fabric suffered structural degradation unrelated to exposure and which may be due to multiple washings.^