PROBLEM TO BE SOLVED: To obtain a medical image diagnostic support device, method, and program capable of acquiring desired information having high reproducibility about an aortic valve annulus part.SOLUTION: A flow path space constituting a portion of a blood flow path formed by an aorta and a left ventricle is specified on the basis of three-dimensional medical image data, and a flow path core C is set in the flow path space. The contour peripheral length of the flow path space in each cross section perpendicular to the flow path core C is calculated along the set flow path core C, and a position at which the contour peripheral length of the flow path space is minimum is specified as an aortic valve annulus position on the basis of the calculation value.
