RESUMO
A new method has been developed for measuring the volume flow rate of blood flowing through large vessels or outflow tracts of the heart. In this article we describe the principle of a method that can reduce the dependence of the Doppler angle of flow measurement by setting the sample points along a line to which every ultrasound beam is perpendicular. To evaluate the accuracy of this method, flow phantom experiments were made for both steady and pulsatile flows. The volume flow rate measured by this method agrees well with that observed by an ultrasound flowmeter (r = 0.99) when the vessel diameter is large (25 mm). However, this method overestimates by 40% when the vessel diameter is small (8 mm). To make this method applicable to small vessels, an improvement in the lateral resolution of Doppler measurement is necessary. It has been concluded that this method can be used to measure the cardiac output or volume flow rates in large vessels.
Assuntos
Débito Cardíaco , Ecocardiografia Doppler/métodos , Algoritmos , Velocidade do Fluxo Sanguíneo , Volume Cardíaco , Ecocardiografia Doppler/instrumentação , Ecocardiografia Doppler em Cores , Ecocardiografia Doppler de Pulso , Previsões , Hemorreologia , Humanos , Aumento da Imagem/métodos , Modelos Cardiovasculares , Modelos Estruturais , Modelos Teóricos , Fluxo Pulsátil , Volume SistólicoRESUMO
A newly-developed noninvasive method was used to measure left coronary blood flow during phantom experiments. Two techniques were used in which: (1) the sample position can always be set in a fluctuating vessel using a wall echo-tracking method with a phase-locked-loop, and (2) the Doppler reference signal was generated separately synchronous with the wall echo signal. These techniques were combined, using a commercially available pulsed Doppler apparatus (SSH-40B: Toshiba). Basic experiments were performed using a blood vessel phantom to verify the validity of these systems. Blood flow velocity in the fluctuating tube could be measured clearly using a vessel-tracking method. The blood flow velocity of the left anterior descending artery was measured in three normal subjects and in seven patients from the third intercostal space along the left sternal border. The velocity pattern was characterized by a crescendo-decrescendo shape in diastole. The peak velocity which appeared in diastole ranged from 19 to 69 cm/sec, with no difference by disease entity. However, in all cases, the blood flow velocity signals were marred by extraneous signals, making it impossible to measure blood flow velocity during systole. Further improvement of the system is mandatory in order to use this flowmeter clinically.
