Image based background magnetic field correction for aortic and pulmonary artery flow measurement using phase contrast

Methods Twelve volunteers underwent breath-hold through-plane phase contrast (PC) imaging of cross sectional view of the ascending aorta and PA. PC imaging was immediately repeated on a static fluid-filled phantom. Phase images were analyzed using QFlow (Medis, Leiden, Netherlands.). Phase shift was also analyzed in static background and in surrounding tissues including chest wall fat and muscle, lung and vertebral body. For PA flow Images only lung and static background were consistently present. Since background phase shift is linearly decreased from anterior to posterior, we calculated background phase shift at the aortic position using linear regression against distance of the aorta from anterior chest wall. Given the proximity of the aortic and PA in z direction the calculated aortic background phase was applied to the PA as well.