The measure of the regurgitant flow through heart valves provides an indication of the severity of the valve closure dysfunction with diagnostic relevance. The estimation of the volume passing through the closed valve during systole, and its ratio with the ejection volume, can significantly improve the assessment of an ongoing valvular pathology. The noninvasive quantification of flow converging to the valve is still lacking a satisfying degree of precision. The most popular technique is the Proximal Isovelocity Surface Area (PISA), which assumes that, in the flow field upstream of the valve, the surfaces corresponding to the same velocity are spherical, whence the regurgitant flow is estimated by multiplication with the hemispherical surface area. In the present study, a new method is proposed of color Doppler echocardiography image processing, for regurgitant flow measurements. In this method, called Proximal Arbitrary Surface Conservative Assessment of Leakage (PASCAL), the laws of fluid dynamics are used to reconstruct the entire flow field, in the hypothesis of axial symmetry, starting from the echographic Doppler mapping of one component of velocity. In vitro experiments have confirmed that the new method provides better flow estimates than PISA, on account of its more rigorous physical model of the regurgitant flow.