Four-Dimensional Magnetic Resonance Velocity Mapping in a Healthy Volunteer With Pseudocoarctation of the Thoracic Aorta
Four-dimensional (4D) velocity mapping technology is used here to evaluate blood flow patterns associated with an incidentally noted, non-hemodynamically significant pseudocoarctation of the proximal descending thoracic aorta in a healthy volunteer (Figure). The 4D phase-contrast magnetic resonance (MR) velocity mapping using time-resolved, cardiac-gated 3-dimensional (3D) velocity data allows for visualization of complex multidimensional blood flow with complete spatial and temporal registration of the region of interest. Four-dimensional velocity mapping is a reliable technique for the analysis and visualization of normal and pathological blood flow features throughout the thoracic aorta. The 4D nature of the data set affords a variety of post-processing options. One visualization technique that has been developed for interpretation of 4D MR data sets is referred to as streamlines. These imaginary lines are aligned with local vector fields and represent the flow field at any given moment throughout the cardiac cycle. Streamlines originate from points on a 2-dimensional grid plane that is arbitrarily positioned within the imaging volume.
Additional Information Regarding Methods
MRI data acquisition consisted of a radio-frequency-spoiled gradient echo sequence with velocity-encoding along all 3 spatial directions. Measurements were respiratory compensated and retrospectively gated to the ECG cycle to generate a CINE series of 3-dimensional data sets. Measurement parameters were TE=2.04 ms, TR=4.97 ms, venc=200 cm/s, FOV=(320×240) mm2, slab thickness =83.2 mm, matrix=(256×144×32), spatial resolution= (1.25×1.67×2.60) mm3, TRes=79.6 ms, total acquisition time =17.8 minutes.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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