Abstract: The invention provides a method of monitoring blood flow in a vertebrate animal subject. Unfocussed plane-wave ultrasound pulses are transmitted into the subject, along a transmission axis, from a single-element ultrasound transducer (2) fastened to the subject (5). Reflections of the ultrasound pulses are received, generating a succession of pulse-Doppler response signals over time. Each pulse-Doppler response signal is processed to determine a first respective spatial-maximum velocity value for blood flowing towards the single transducer element (2), and a second respective spatial-maximum velocity value for blood flowing away. Heartbeats are identified from said spatial-maximum velocity values and a quality metric is assigned to each identified heartbeat. A subset of the spatial-maximum velocity values is identified for which the assigned quality metric exceeds a threshold level.

Abstract: A system for monitoring blood flow in a patient, the system comprising: a single-element disc-shaped ultrasound transducer for fastening to the patient and a controller subsystem. The controller subsystem is configured to: control the ultrasound transducer to transmit a series of plane-wave pulses into the patient in a propagation direction; sample reflections of the plane-wave pulses, received at the ultrasound transducer, from a region within the patient, to generate pulse-Doppler response signals; and process the pulse-Doppler response signals to calculate a blood flow curve for waveform analysis.

Abstract: A system for monitoring blood flow in a patient comprises a first unit having an ultrasound transducer and a fastener for fastening the unit to the patient. A controller subsystem comprises the first unit and a separate second unit. The controller subsystem is configured to: control the ultrasound transducer to transmit plane-wave pulses into the patient in a propagation direction; sample reflections of the plane-wave pulses, received at the ultrasound transducer, from a region within the patient, to generate pulse-Doppler response signals; and process the pulse-Doppler response signals to estimate a series of values, over time, of a measure proportional, but not equal, to the total blood volume flow passing through the region. A monitoring subsystem is configured to monitor the series of values over time and to generate a signal if a set of one or more of the values satisfies a predetermined criterion.