Status of blood banking and the blood supply in Afghanistan.

BACKGROUND: As a result of more than 20 years of war in Afghanistan, its blood supply system has been damaged. We carried out an assessment of that blood supply system to determine the type and extent of assistance needed to increase blood availability and safety. STUDY DESIGN AND METHODS: An assessment tool was developed, daily activities in Afghanistan were observed, and key personnel were interviewed. RESULTS: Because there was no donor recruitment organization, most blood was obtained by the family replacement system. There was an inadequate supply of stored blood, which led to use of blood before screening test results for transfusion-transmitted disease were complete. Whole blood was provided but blood components were not produced. Blood was tested intermittently for human immunodeficiency virus Types 1 and 2, hepatitis B surface antigen, hepatitis C virus, and syphilis using agglutination-based screening methods. CONCLUSIONS: A dedicated staff is in place but to strengthen the blood supply system in Afghanistan, it will be important to address infrastructure and facilities, organization, standard operating methods, supplies and equipment, training, quality assurance, and transfusion medicine education.

Spatial dependence of the nonlinear BOLD response at short stimulus duration.

Most functional magnetic resonance imaging studies use linear models to predict the measured response by convolution of an impulse response with the stimulus profile. Using very short visual presentation times (<2 s), deviation from the linear model in the measured BOLD data from the human brain was found for the response integral, amplitude, and width. In this study, high temporal and spatial resolution were used to quantify nonlinear effects and investigate the spatial dependence. Data at 4 Tesla showed at short stimulus duration a nonlinearity, i.e., deviation from a linear model, with an index up to 400%, whereas data at 7 Tesla exhibited a nonlinearity index up to 40%. The effect was more pronounced for response amplitude than for response area. A reduced width and sharpening of responses at shorter stimulus duration was also found. A voxel-based analysis of 7 Tesla data with 1.2 x 1.2 x 2 mm(3) resolution revealed a correlation between response onset and nonlinearity index. This suggests that the nonlinearity effects are a tissue-specific phenomenon and are likely to be more localized to the site of neuronal activity. The observed magnetic field dependence and the demonstrated nonlinearity in the response width support the hypothesis that the source of the nonlinearity at short stimulus duration has a considerable hemodynamic contribution. The nonlinearity was modeled as a "switch"-type initial hemodynamic response onset. Understanding these nonlinearities in the BOLD response is important for design and the analysis of rapid event-related fMRI experiments with brief stimulus presentations.