Cognitive difficulty of a peripherally presented visual task affects head movements during gaze displacement

Characterization of flow properties of an artificial ventricle may aid development of designs to minimize thrombosis. Techniques for determining two such flow properties, viz. ventricular clearance rate and ejection fraction, are compared and validated here for polyurethane and silicone rubber ventricles operated in a mock circulatory loop at various stroke volumes and pulse rates. Ventricular clearance rats were measured both by clinical radionuclide tracer techniques and by an optical tracer method. Ejection fractions were measured by radionuclide imaging and validated by direct measurements of flow rate and ventricular volume. Results from the two methods for ventricular clearance are in close agreement. The optical tracer method is superior in spatial resolution, convenience and economy, but the radionuclide tracer method for ejection fraction gives excellent agreement with the absolute measurements.