Phase Contrast (PC) Cardiac MRI imaging

    Cine PC is a gradient echo pulse sequence in combination with ECG triggering or gating. This technique is used to assess flow volumes and velocity profiles across valves and shunts.  
·        By using the PC data, one is able to calculate mean spatial velocities; instantaneous flow per phase, flow per cardiac cycle and thus flow volumes in ml/min. This technique accurately assesses high velocities up to 600 cm/s if TE is reduced down to 8 ms. Velocity encoding value (VENC) chosen by the operator should be as close as possible to but still greater than the expected peak systolic velocity for obtaining reliable results. The VENC is described as the maximum velocity that will be properly encoded by the sequence. For patients less than 65 years of age with normal cardiac function, normal range is from 0.1 to 200 cm/s. Typical VENC for between 170 cm/s and 220 cm/s is recommended. For older patients with congestive heart failure, elevated serum creatinine, or aortic aneurismal disease, a VENC of < 100 cm /s is more appropriate. In case of vessel or valve stenosis, higher flow velocities up to 600 cm/s, due to turbulent jets, may be present. If the flow velocity is higher than chosen VENC such as jet flows caused by stenoses, flow direction will be miscoded as opposite to actual flow direction. This results in aliasing phase wraps), and leads to wrong quantification of flow speed and pressure gradients.
·        Mitral Valve PC Flow: Mitral valve flow acquisition is planned on the end-systolic 2C and 4C images. The center of the slice is placed in the middle of mitral valve and angulated parallel to the mitral valve.
·        Tricuspid Valve PC Flow: Tricuspid valve flow acquisition is prescribed on the right ventricle 2C long axis images. This is prescribed from 4C images. The centre of the slice is positioned in the middle of tricuspid valve and slice is angulated through the right ventricle apex. The slice should pass through the right ventricle apex on both end-systolic and end-diastolic 4C images. From 4C and right ventricle 2C images tricuspid valve flow acquisition is planned. The center of the slice is placed in the middle of tricuspid valve and angulated parallel to the tricuspid valve.

--> ·        Pulmonary Arteries PC Flow: Imaging planes through the left pulmonary artery (LPA) and right pulmonary artery (RPA) should be perpendicular to the direction of flow and proximal to the first branching vessel. These planes in adults are usually located 1–1.5 cm distal to the main pulmonary artery (MPA) bifurcation.
·        Ascending Aorta PC Flow: The flow acquisition through the ascending aorta is prescribed from the coronal localizer. Flow measurement is performed perpendicular to the flow direction usually 1.5–2 cm above the aortic valve (pulmonary bifurcation level).
·        MPA PC Flow: For planning the MPA flow acquisition, an additional imaging plan is necessary. This plan is prescribed from sagittal localizer. A few slices parallel to the MPA are obtained. Then, on these images, a slice perpendicular to the MPA is set for PC flow acquisition.