An ultrasound scanner comprising a battery and configured to process ultrasound measurements to determine a level of movement of the probe； if the level of movement meets an inactivity criterion, reducing the pulse rate of the probe. Reducing the pulse rate of the probe may comprise: reducing the number of scan lines, increasing the period between the frames and/or periodically stopping generating ultrasound pulses for a period of time and then restarting. The amount of movement may be determined by analysing changes in the measurement data between repeated measurements of the same scan positions. The changes analysed may be the strength of the echoes from corresponding positions. The reduction of pulse rate of the probe may be a progressive reduction based on the amount of movement detected between different modes of reduction (e.g. scan lines, frame period, temporary hibernation). The scanner may increase the pulse rate based on the level of movement of the probe. The increase may also be progressive. A further invention relates to reducing the pulse rate of the probe based on exceeding a temperature threshold.
