1. An ultrasound imaging system comprising: an image acquisition head; a processor configured to: locate a needle tip by projection transformation onto at least one plane; determine a needle line in an ultrasound image data volume; determine, based on the needle line, a needle plane in the ultrasound image data volume comprising the needle line; determine a difference between the needle plane and an acquisition plane acquired by the image acquisition head; and generate an indication for display of the difference between the needle plane and the acquisition plane to a user of the system.