An ultrasound probe system for guiding introduction of an instrument into a patient includes a disk having a surface and an open channel passing axially through the disk and at least two ultrasound transducer elements disposed on the surface of the disk in a parallel arrangement. The open channel is configured to receive the instrument therethrough to permit alignment of the instrument with respect to the disk. Each of the ultrasound transducer elements is configured to transmit and receive ultrasonic waves for detecting an anatomical structure. A graphical representation of at least a portion of the anatomical structure can be provided for guiding the introduction or insertion of the instrument into the anatomical structure.
