Quantitative Cardiac Output Assessment Using 4D Ultrafast Doppler Imaging: An in Vitro Study

Background, Motivation and Objective Echocardiography is routinely used in the clinic to evaluate the cardiac function. Anatomical indexes such as ventricular volume measurements or functional indexes such Cardiac Output are performed using standard echocardiography. However, 2D dimensional measurements induce inter-operator variability and standard 3D measurements do not have the sufficient volume rate to evaluate functional indexes. Moreover, the accuracy of flow velocity estimates is strongly reduced by the angular dependence of Doppler measurements. In this study, we propose to use 4D ultrafast Doppler to evaluate flow rates in a pipe to demonstrate the potentiality of performing Cardiac Output measurements without assumptions on the valve geometry and without angular dependence. Statement of Contribution/Methods An ultrasonic matrix array probe (central frequency 2.5MHz, 1024 elements, pitch 0.3 mm, bandwith 60%, Vermon, France) connected to a 1024 channels ultrasound scanner prototype was used to image the pipe output in three dimensions. 500 diverging waves (angular aperture 80°) were emitted at a volume rate of 2000 volumes/s during 250 ms. Color Doppler volumes (quantitative flow speed volumes) were computed by calculating the first moment of the Doppler spectrums in each voxel. The pipe flow rates (N=7) were calculated by integrating directly the flow speed over the cross section of the pipe. Results/Discussion The measured flow rates were found to be in a good agreement with the flowmeter values used as a gold standard (R2 = 0.96). The four dimensional nature of the acquisition has the potential to enable the calculation of the Cardiac Output in vivo in patients without the need of making any assumption on the valve geometry or the direction of the ultrasonic beam usually responsible for errors.