Interactive visualization of 4-D parametric fields

Parametric images are generated from the analysis of image data to help characterize the functional information present in the original images. They address the need for enhancing the spatial and temporal resolutions for analysis. Parametric fields provide an underlying (usually smooth) model that can be evaluated at any image location using its analytical formulation. To facilitate interactive display and analysis of such fields, we developed a visualization scheme that can help directly render the parametric field using graphics interpolation methods. This eliminates the need for high resolution storage of such data for visualization purposes. The major advantage of such an approach is that graphics hardware can be used to accelerate the interpolation, thus achieving substantial improvement in the performance. Successive derivative parametric images, such as velocity or acceleration maps from the motion fields, can be displayed in real-time. The example presented here is the 4D B-spline based motion field representation of the cardiac-tagged MR images. A motion field with 7×7×7×15 control points shown to adequately describe the full motion of the heart during cardiac cycle. Using this field, material points can be tracked over time and local mechanical properties (e.g.: strain) can be computed. The visualization method presented here utilizes the similarity between the B-spline representation of the motion fields and the graphics hardware support for NURBS display with texture mapping to achieve high performance visualization of these parametric fields.