A novel method for the assessment of the accuracy of computing laminar flow stroke volumes using a real-time 3D ultrasound system: In vitro studies

Aims

Laminar flow stroke volume (SV) quantification in the ascending aorta or pulmonary artery can provide a measure for determining cardiac output (CO). Comparing flows across different valves can also compute shunt volumes and regurgitant fractions. Quantification methods for 3D color Doppler laminar flow volumes have been developed using reconstructive 3D, but these are cumbersome and time-consuming both in acquisition and measurement. Our study evaluated newly developed color Doppler mapping with real-time live 3D echo to test velocity, spatial and temporal resolution for computing SV.

Methods and results

Five rubber tubes (diameters=3.0, 2.25, 2.0, 1.9, 1.7cm), a freshly dissected porcine aorta (Ao) and a pulmonary artery (PA) (both 2–3cm diameter) were connected to a pulsatile pump in a water bath. Different SV, from 10 to 80ml/beat, were studied at pump rates of 40–60bpm in this phantom model with flow quantified by timed collection. The Nyquist limit was set between 43 and 100cm/s and frame rate ranged from 14 to 23/s. ECG triggered 3D color Doppler volumes were acquired with a 2–4MHz probe. The digital scan line data from the 3D volumes, with retained velocity assignments, was exported and analyzed offline by MatLab custom software. Close correlations were found between 3D calculated SV and reference data for all tubes ( r =0.98, y =1.14 x −1.69, SEE=2.82ml/beat, p <0.0001). Both Ao and PA flows were also highly correlated with the reference measurements (PA: r =0.98, SEE=3.17ml/beat; Ao: r =0.99, SEE=3.20ml/beat).

Conclusions

Real-time 3D color Doppler method could provide an efficient, accurate and reliable method for clinical evaluation and quantification of flow volumes in patients.