Quantification of valvular regurgitation area and geometry using HPRF 3-D Doppler

It is important to determine the severity of valvular regurgitation accurately because surgery is indicated only in severe regurgitations. The evaluation of, for example, mitral regurgitation is complex, and the current methods have limitations. We have developed a 3-D Doppler method to estimate the cross-sectional area and the geometry of a regurgitant jet at the vena contracta just downstream from the actual orifice. The back-scattered Doppler signal from multiple beams distributed over the area of interest was measured. The received power from these beams was then calibrated using both a priori knowledge of the lateral extent of the beams and a reference beam that was completely enclosed by the vena contracta. To isolate the Doppler signal received from the core of a regurgitant jet, a high pulse repetition frequency and a steep clutter filter are required. The method has been implemented and verified by computer simulations and by in vitro experiments using a pulsatile flow phantom and prosthetic valves with a range of holes. We were able to distinguish between mild, moderate, and severe valvular regurgitation. We were also able to quantify the regurgitational area as well as show the geometry of the regurgitation.