Multiplanar ultrasonic vascular imaging device and protective sheath

An apparatus, method and system for cannulation of blood vessels. The apparatus comprises a sensor assembly including two linear transducer arrays oriented perpendicular to each other to form a "T" shape to provide ultrasound images of at least one blood vessel in a portion of a patient's body in two perpendicular planes. The sensor assembly may have graphic markings on an exterior surface thereof to facilitate orientation of the sensor assembly on the patient and guidance of a needle toward a desired target vessel during the cannulation procedure. The sensor assembly may also include an associated structure to cooperate with a reference location element to place, align and secure the sensor assembly to the patient's skin at a desired location.