Method and apparatus for measuring volume fluid flow

摘要

A system is provided for measuring volume blood flow using non-invasive ultrasonic Doppler techniques. This system includes a probe assembly including a transducer having an inner transducer element and a concentric outer transducer element. A wide beam of ultrasonic energy is transmitted using the transducer and is received by a lumen area. Reflected untrasonic energy is returned to the transducer. Both the outer and inner transducer elements of the transducer are used to generate signals representative of a wide beam and a narrow beam. These generated signals include Doppler information. The signals representative of the wide beam are processed simultaneously with signals representative of the narrow beam to produce Doppler power spectrums associated with the wide and narrow beams. Phase quadrature signals are also generated for use in determining the direction of blood flow at the insonified lumen area. An AGC circuit is utilized for controlled amplitude fluctuations in the wide beam Doppler power spectrum. The control signal is also applied to the narrow beam power spectrum to avoid the introduction of inaccuracies in the subsequent computation of the ratio of wide beam power to narrow beam power. A mean frequency estimator circuit is also provided for determining the velocity of the blood flow at the insonified lumen area. The determined flow velocity is applied to a recording device for observation by the operator. The operator relies on the flow velocity trace in ensuring correct placement of the probe assembly for insonifying a desired lumen area. After it has been determined that the probe assembly is properly located, a processing/controlling unit determines volume blood flow by multiplyng the determined flow velocity by the ratio of the obtained powers in the wide and narrow beams.