Flow Sensitive 4D Magnetic Resonance Imaging (MRI)
 
Recent advances in medical imaging technology have allowed the acquisition of high-resolution, transient, three-dimensional images of blood flows within the human circulatory system. It is only natural that EnSight, widely used for visualizing blood flows computed in CFD simulations, be applied to the visualization of such complex medical imaging data providing compressive anatomical (blood vessel) and functional (blood flow) coverage of an entire organ of interest. 

The first attempts to apply EnSight to this field were made in joint studies performed by Sweden's Linkoeping University and the University of California in San Francisco in the mid 1990s. Today, EnSight is routinely used for blood flow studies at these universities and at other leading research groups such as the Lucas Center and department of Radiology at Stanford University (USA), the Department of Neuroradiology at the University Hospital of Basel (Switzerland) and the Medical Physics Group at the University Hospital of Freiburg (Germany). 

Below is a brief summary of the method, recent results and several references to articles in medical literature on this unique application of EnSight in the medical field. CEI has established a partnership with the Department of Diagnostic Radiology, Medical Physics at the University Hospital of Freiburg, a leading user of EnSight for flow sensitive 4D MR imaging, to aid others interested in using the software. 
 
For details, contact:
 
PD Dr. Michael Markl
Department of Diagnostic Radiology, Medical Physics
University Hospital Freiburg, Germany
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Flow-Sensitive 4D MRI and EnSight
 
Magnetic Resonance Imaging (MRI) offers the unique possibility to analyze both structure and function of the human body and has - as a result of major technical developments and widespread availability - gained increased importance. 

MRI provides a non-invasive method for the highly accurate anatomic characterization of the heart and great vessels in 3D. In addition, the intrinsic sensitivity of MRI to flow, motion and diffusion offers the unique possibility to acquire spatially registered functional information simultaneously with the morphological data within a single measurement. 
 
3D spatial encoding combined with flow sensitive MRI offers the possibility to measure and visualize the temporal evolution of complex flow patterns within a 3D-volume. To exploit the advantages of such a volumetric approach, a MR technique (flow sensitive 4D MRI) was developed at the University Hospital Freiburg that permits the acquisition of anatomical and three-directional velocity information over the entire cardiac cycle for each pixel within a 3D-volume. 
 
The technique has been quantitatively validated and successfully applied in human studies. In healthy volunteers, typical flow features such as helical flow in the ascending aorta could reliably be detected and illustrate the benefit of the complete temporal and spatial coverage available in the 4D MRI data sets. Using EnSight, visualization of global and local flow features can be performed freely within the 3D volume at any time following the actual scan. In patients with common vascular pathologies, complex and potentially pathological flow could be identified. Specifically, relatively small geometric changes, e.g. mildly enlarged ascending aorta, resulted in major disturbances of local blood flow patterns within and even further downstream to the pathology.  

Fig. 1: Flow sensitive in-vivo 4D MRI in a normal thoracic aorta. Time-resolved 3D particle traces demonstrate normal systolic filling of the aorta and supra-aortic branches (color coding = absolute local velocity).Fig. 1: Flow sensitive in-vivo 4D MRI in a normal thoracic aorta. Time-resolved 3D particle traces demonstrate normal systolic filling of the aorta and supra-aortic branches (color coding = absolute local velocity).

Fig. 2: Example for anatomical and blood flow visualization in a patient with enlarged aorta (ascending aortic aneurysm, arrows). A: Maximum Intensity projection (MIP) of a coronal MR- Angiogram (MRA) B: Thin slab MIP, reformatted to a sagittal plane. C: Reconstructed thoracic aortic geometry using intensity based surface rendering. D: Late systolic streamlines reflecting the considerable helical flow in the region of the enlarged aorta.

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Examples
German Researchers use EnSight to Unlock Mysteries of the Circulatory System
3D Visualization Used in Engineering Finds a Home in Human Heart Research, linkoping.pdf
Featured Image - Magnetic Resonance Scans