Abstract: A needle guiding apparatus transmits ultrasonic sound waves through a hollow hypodermic needle. The sound waves travel down the needle and a portion of the energy in the sound waves is reflected back up the needle by the tissues at which the needle is pointed. If the needle is pointed at a vessel in which blood is flowing, the frequency of the reflected sound waves is Doppler shifted by an amount proportional to the velocity of blood cell flow in the vessel. The needle guiding apparatus detects and amplifies the Doppler shifted signal and the resulting signal is used to drive a speaker and thereby generate an audible signal. As the needle is brought closer to the vessel, the Doppler sounds become stronger in amplitude and the angle of the needle with respect to the vessel affects the pitch of the Doppler shifted signal. These audible indications are used by the clinician, while varying the angle of the needle, to identify the proper direction to proceed in order to insert the needle in the vessel.

Abstract: An ultrasonic transducer apparatus includes an ultrasonic transducer coupled to a backing member, with a cylindrically shaped hole for accepting a hypodermic needle. The transducer transmits ultrasonic sound waves through the skin and toward the vessel of interest. A portion of the energy in the sound waves is reflected by blood cells flowing within an underlying vessel. The reflected energy is "Doppler shifted" in frequency from the transmitted sound waves because the blood cells are moving relative to the position of the transducer, with the shift in frequency being proportional to the velocity of the blood cells flowing in the vessel. The Doppler shifted reflected signal is detected and amplified and then used to drive an audio speaker, thereby generating an audible signal. As the needle is brought closer to a vessel, the Doppler sounds become stronger in amplitude and the angle of the needle with respect to the vessel affects the pitch of the Doppler shifted signal.

Abstract: A phased array acoustic transducer apparatus has a controller and an array of ultrasonic transducers mounted in a water tight housing. Also included in the water tight housing are a transmitter circuit which sends phased excitation signals to the array of ultrasonic transducers so as to generate a directed beam of acoustic energy. A receiver circuit, located in the water tight housing, processes and combines signals received by the array of ultrasonic transducers to generate an output signal. The controller sends both power and control signals via a cable to the transmitter and receiver circuits. The cable uses a simple serial data line and a clock signal line to transmit beam angle control signals, thereby minimizing the size of the cable. The controller sends transmitter gating signals over a gate signal line on the cable to enable and disable operation of the transmitter circuit, such as is required for a pulse-echo mode of operation.