Doppler ultrasound tracking instrument for monitoring blood flow

There are situations, during surgery, in the immediate post-operative period, and in neonatal and adult intensive care units, where monitoring the blood supply to a certain organ or region of the body could be of great value. Doppler ultrasound has great potential for monitoring blood flow velocity because it is a reliable, noninvasive method and produces results in real time. In addition, the development of Doppler technology associated with the recent progress of electronics and computerization has widened the range of information that can be extracted from the Doppler signal. Despite its great potential, there are difficulties which prevent the establishment of blood flow monitoring as a valuable clinical tool. Amongst these difficulties the one which appears to be the most important is the problem of fixing the transducer to the patient in order to prevent misalignment between ultrasound beam and vessel caused by patient movement. A Doppler tracking instrument which is able to adjust its beam direction automatically to ensure correct alignment between the beam and vessel would be valuable in overcoming this difficulty. The work described in this thesis led to the design, construction, and testing of hardware and software for such an instrument, which consists of a feedback controlled phased array transceiver, driving a one dimension array continuous wave Doppler transducer. With its operation it was possible to demonstrate the principle of Doppler tracking, which can open a wide area of monitoring to clinical ultrasound. From the construction point of view, this equipment was useful in identifying some guide lines to be followed in order to turn it into a device which can be used as a clinical tool.