An ultrasound imaging apparatus for imaging a region of interest in a subject, comprising: a control unit (1, 10, 30, 50); a plurality of separate ultrasonic probes (2a-2c; 12a-12d; 32a-32d; 70) coupled to the control unit, each probe comprising: at least one transducer for transmitting and receiving ultrasonic waves; a receiver for receiving a probe scan signal for triggering an ultrasound scan by the probe; and an output for providing an ultrasound image; wherein the control unit is adapted to: control the probes to coordinate their operation in a predetermined probe sequence by providing a probe scan signal to at least one of the probes; and receive ultrasonic images from the outputs of the probes, for the generation of a combined display of the images from the probes; and wherein the apparatus is configured to coordinate the operation of the probes in the predetermined probe sequence either: by each probe transmitting a scan state signal indicative of its own scan being completed, for reception by the next probe in the probe sequence as the probe scan signal, or by the control unit for sending the next probe in the probe sequence a probe scan signal; or by each probe storing a local clock synchronized to a global clock common to the probes, and responding to the probe scan signal from the control unit to execute its own scan at a scan timing based on its local clock. a control unit (1, 10, 30, 50); a plurality of separate ultrasonic probes (2a-2c; 12a-12d; 32a-32d; 70) coupled to the control unit, each probe comprising: at least one transducer for transmitting and receiving ultrasonic waves; a receiver for receiving a probe scan signal for triggering an ultrasound scan by the probe; and an output for providing an ultrasound image; at least one transducer for transmitting and receiving ultrasonic waves; a receiver for receiving a probe scan signal for triggering an ultrasound scan by the probe; and an output for providing an ultrasound image; wherein the control unit is adapted to: control the probes to coordinate their operation in a predetermined probe sequence by providing a probe scan signal to at least one of the probes; and receive ultrasonic images from the outputs of the probes, for the generation of a combined display of the images from the probes; control the probes to coordinate their operation in a predetermined probe sequence by providing a probe scan signal to at least one of the probes; and receive ultrasonic images from the outputs of the probes, for the generation of a combined display of the images from the probes; and wherein the apparatus is configured to coordinate the operation of the probes in the predetermined probe sequence either: by each probe transmitting a scan state signal indicative of its own scan being completed, for reception by the next probe in the probe sequence as the probe scan signal, or by the control unit for sending the next probe in the probe sequence a probe scan signal; or by each probe storing a local clock synchronized to a global clock common to the probes, and responding to the probe scan signal from the control unit to execute its own scan at a scan timing based on its local clock. by each probe transmitting a scan state signal indicative of its own scan being completed, for reception by the next probe in the probe sequence as the probe scan signal, or by the control unit for sending the next probe in the probe sequence a probe scan signal; or by each probe storing a local clock synchronized to a global clock common to the probes, and responding to the probe scan signal from the control unit to execute its own scan at a scan timing based on its local clock.