Physics Just the Basics Series #06 - Flow MRI using Phase Contrast-Flow MRI using Phase Contrast

Video Transcription

Video Summary

The webinar introduced the basics of phase contrast flow MRI for clinicians and researchers. After welcoming remarks and speaker introduction, Johannes Togger explained why flow imaging matters clinically, especially for detecting shunts and valvular or congenital heart disease, using two case examples. He then reviewed core MRI physics: magnetization, phase, gradients, and how bipolar gradients encode motion into phase shifts proportional to velocity. He described the standard 2D flow sequence, where paired acquisitions cancel background phase and allow calculation of vessel flow by segmenting the vessel, averaging velocity over the ROI, and integrating flow over time to obtain stroke volume.<br /><br />The talk emphasized common pitfalls, especially aliasing from too low VENC and phase background errors from scanner-related offsets, which can cause major flow underestimation. Other issues included plane misalignment, partial volume effects, and turbulent flow in stenosis. He discussed mitigation strategies such as choosing appropriate VENC, background correction, phantom correction, and careful protocol validation.<br /><br />Finally, he covered validation approaches, noting that flow measurements should be checked against expected internal consistency, and briefly introduced advanced methods: real-time flow MRI for arrhythmias and physiology, and 4D flow MRI for whole-heart volumetric assessment. A Q&A followed on practical issues like segmentation, breath-hold vs free-breathing, coil choice, prosthetic valves, and software correction tools.

Keywords

phase contrast flow MRI

MRI physics

velocity encoding

background phase correction

aliasing

stroke volume

4D flow MRI

cardiac flow imaging

congenital heart disease