A device having a needle injector pivotally attached to an ultrasound transceiver is operated to place a sterilizable needle or needle/cannula unit within a blood vessel by a single user-device operator in which the blood vessel is made visible in a monitor image by ultrasound insonification. A guidance template is overlapped on at least one of a transverse, longitudinal, or three-dimensionally imaged blood vessel that illustrates a predicted path of the needle when it undergoes movement implemented by a controller. In alternate embodiments the needle injector, ultrasound transceiver, and needle or needle/cannula unit may be contained within a flexible sheath that is capable of being sterilized.