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(Circulation. 2004;109:3221-3222.)
© 2004 American Heart Association, Inc.

Images in Cardiovascular Medicine

Four-Dimensional Magnetic Resonance Velocity Mapping in a Healthy Volunteer With Pseudocoarctation of the Thoracic Aorta

Michael D. Hope, BA, BS; Jonathan M. Levin, MD; Michael Markl, PhD; Mary T. Draney, PhD; Marc Alley, PhD; Robert J. Herfkens, MD

From the Departments of Radiology (M.D.H., J.M.K., M.M., M.A., R.J.H.) and Biomechanical Engineering (M.T.D.), Stanford University School of Medicine, Stanford, Calif.

Correspondence to Robert Herfkens, MD, Department of Radiology, Stanford University School of Medicine, Lucas Center for MR Spectroscopy and Imaging, P263, 1201 Welch Rd, Stanford CA, 94305–5488. E-mail herfkens{at}stanford.edu

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.

View larger version (54K): [in this window] [in a new window]   A 4D velocity mapping study of a healthy, middle-aged volunteer. A, 3D contrast-enhanced magnetic resonance angiography prescribed in the oblique-sagittal orientation, demonstrating ectasia of thoracic aortic arch with a pseudocoarctation pattern. The remainder of the aortic contours are smooth, without evidence for regional stenosis or dilatation. A normal anatomic variant bovine arch, with the left common carotid artery arising from the brachiocephalic artery, is incidentally visualized. B, Streamlines, released from a 2-dimensional grid plane at the level of the ascending aorta, demonstrate the 3D magnitude of the local systolic blood flow. The 3D streamlines reflect the instantaneous velocity vector field in a given systolic time frame through the thoracic aorta. A prominent vortical flow pattern is demonstrated distal to the pseudocoarctation (arrow). Considerable variation in the magnitude of local blood flow velocities and regions of high flow is identified by the wide range of color-coding of the streamlines in the proximal descending thoracic aorta. C, Normal 4D flow study with similar streamline analysis for comparison.

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=(320x240) mm², slab thickness =83.2 mm, matrix=(256x144x32), spatial resolution= (1.25x1.67x2.60) mm³, T_Res=79.6 ms, total acquisition time =17.8 minutes.

Footnotes

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.

Circulation encourages readers to submit cardiovascular images to the Circulation Editorial Office, St Luke’s Episcopal Hospital/Texas Heart Institute, 6720 Bertner Ave, MC1-267, Houston, TX 77030.

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hope, M. D. Articles by Herfkens, R. J. Search for Related Content PubMed PubMed Citation Articles by Hope, M. D. Articles by Herfkens, R. J. Related Collections Cardiovascular imaging agents/Techniques CT and MRI CV surgery: aortic and vascular disease