Interventional cardiac MRI has been undergoing rapid development because of the availability of MRI compatible
interventional catheters, and the increased performance of the MRI systems. Intravascular techniques do not require an
open access scanner, and hence higher imaging performance during procedures can be achieved. Now, with the
availability of a short, relatively open cylindrical bore scanner high imaging performance is also available to guide
direct surgical procedures.
KEYWORDS: Real time imaging, 3D image processing, Magnetic resonance imaging, Volume rendering, Stereoscopy, Visualization, Medium wave, Laser scanners, 3D scanning, Data acquisition
A system has been developed to produce live 3D volume renderings from an MR scanner. Whereas real-time 2D MR imaging has been demonstrated by several groups, 3D volumes are currently rendered off-line to gain greater understanding of anatomical structures. For example, surgical planning is sometimes performed by viewing 2D images or 3D renderings from previously acquired image data. A disadvantage of this approach is misregistration which could occur if the anatomy changes due to normal muscle contractions or surgical manipulation. The ability to produce volume renderings in real-time and present them in the magnet room could eliminate this problem, and enable or benefit other types of interventional procedures. The system uses the data stream generated by a fast 2D multi- slice pulse sequence to update a volume rendering immediately after a new slice is available. We demonstrate some basic types of user interaction with the rendering during imaging at a rate of up to 20 frames per second.
Rapid analysis of large multi-dimensional data sets is critical for the successful implementation of a comprehensive MR cardiac exam. We have developed a software package for the analysis and visualization of cardiac MR data. The program allows interactive visualization of time and space stacks of MRI data, automatic segmentation of myocardial borders and myocardial tagging patterns, and visualization of functional parameters such a motion, strain, and blood flow, mapped as colors in an interactive dynamic 3D volume rendering of the beating heart.
Tracking of magnetic resonance (MR) tags in myocardial tissue promises to be an effective tool in the assessment of myocardial motion. The amount of data acquired is very large and the measurements are numerous and must be precise requiring automated tracking methods. We describe a hierarchy of image processing steps that estimate both the endocardial and epicardial boundaries of the left ventricle and also estimate the spines of radial tags that emanate outward from the left ventricular cavity. The first stage determines the position of the myocardial boundaries for each of 128 rays emanating from the origin. To counter the deleterious effects of noise and the presence of the tags when determining the boundary positions we use nonlinear filtering concepts from mathematical morphology together with a prion knowledge related to boundary smoothness to improve the estimates. The second stage estimates the tag spines by matching a template in a direction orthogonal to the expected tag direction. We show results on tagged images and discuss further research directions. 1.
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