On the use of three-dimensional Doppler acquisition for real-time volume flow estimation.

Abstract

Clinical volumetric blood flow estimation relies on several assumptions. Among them are cylindrical vessel geometry, symmetric flow profile, and Doppler angle. None of them are known well enough to obtain clinically relevant estimates. 3-D color flow acquisition circumvents these assumptions, posing a viable tool for in vivo blood volume flow analysis. A 4-D cardiac scanner operating a 2-D array for real-time 3-D color flow imaging [GE Healthcare, Milwaukee, WI] was used. The array was positioned to fully intersect a 2-cm-diameter flow tube with the constant-depth plane (CPlane). Blood mimicking fluid was circulated at up to 6 l/min using a cardiac bypass pump (60 and 80 beats/min). A trigger source synchronized the pump and scanner. Data volumes were acquired equally spaced throughout the cardiac cycle. Temporally resolved volume flow was derived from CPlane data integration using Doppler power partial volume correction. Results show less than 7% mean flow error for temporally resolved volume flow (100 points per cardiac cycle and 50 averages). Single points in the cardiac cycle (10 max total), including systolic and diastolic flow, can be acquired within 50 heartbeats. Average, nontime-resolved flow can be estimated within 5 s.