Blood viscosity is altered in diseases such as sickle cell anemia, hypertension, and atherosclerosis and also during coagulation, but its measurement requires complex and expensive instrumentation and is thus rarely done. We propose to develop an ultrasonic technique to simplify this measurement using small samples of blood. An ultrasound beam produces streaming in fluids, and a pulsed Doppler velocimeter can be used to both induce and measure the streaming velocity which is determined by both the acoustic and physical properties of the fluid. In addition, the time constant to a step change in acoustic power is also a function of viscosity and density. We propose during Phase I to develop a 20 MHz pulsed Doppler and signal processing to show: 1) that streaming can be measured in 50 mu1 of canine or murine blood with a 1 mm transducer; 2) that the streaming velocity and time constant are functions of viscosity; and 3) that streaming is reproducible and stable. During Phase II we will model the streaming process using finite difference methods, and based on the results will design an instrument and apparatus optimized for measuring viscosity in small samples of freshly drawn whole blood. This technique could also become the basis of a whole-blood coagulation detector and timer and could be incorporated into a laboratory analyzer. In research it will be used to study hemorheology in genetically altered mice.
The testing of blood is a major activity in hospital laboratories, and the concepts to be developed here could be incorporated into the measurement of coagulation timing and viscosity. The measurement of blood viscosity at the bedside for diagnosis and for monitoring of therapeutic manipulations is essentially a new market where the implications could be very great.
