Development of non-invasive diagnostic indices often requires accurate blood-flow calculation using physiologically realistic velocity profiles as boundary conditions. In this research, a methodology is being developed and validated that can directly use phase-contrast MR imaging (PC-MRI) based velocity measurement to perform blood-flow computation with patient-specific geometry. Using this methodology, the pressure drop can also be calculated non-invasively. Although the main focus of our research has been pulmonary insufficiency (PI) in tetralogy patients, our method can be employed in many other patho-physiologies. As a pilot study, the methodology is tested using a simple model of blood-flow through a straight artery of uniform cross-section.