Exploring hemodynamics by raycasting 4D MRI flow

Flow sensitive phase-contrast magnetic resonance imaging sequences produce three-dimensional velocity fields in time, providing quantitative information of blood flow dynamics. Thorough understanding of the hemodynamic behavior will support physicians to diagnose and assess risk of various cardiovascular diseases. However, inspection of the complex cine flow data, encompassing both morphology and function, is generally a troublesome and tedious task. Over the last few decades, the field of scientific flow visualization has introduced a multitude of techniques to explore unsteady velocity fields, in order to capture and depict flow characteristics. Inspired by concepts from ultrasound imaging, we have investigated raycasting as a means to explore and visualize direction and magnitude of blood velocities, striving to reveal the blood flow behavior. In particular, we aim to depict flow patterns that deviate from the expected blood flow. For that purpose, several interaction techniques have been incorporated into the presented framework. Angles between a user-defined direction, set by an interaction widget, and the velocity field are mapped to different visual cues using a transfer function. Furthermore, we define the prevalent flow as approximate of the expected blood flow, generated based on the vessel centerline. We visualize a projection of the angles between the prevalent flow and the velocity field.

@InProceedings { POBGHV10,
  author       = "Pelt, R.F.P. van and Bescos, Javier Olivan and Breeuwer, Marcel and Groeller, Meister Eduard and Haar Romeny,
                  B.M. ter and Vilanova, Anna",
  title        = "Exploring hemodynamics by raycasting 4D MRI flow",
  booktitle    = "Proceedings of the Annual Conference of the Advanced School for Computing and Imaging (ASCI 2010), 1-3
                  November 2010, Veldhoven, The Netherlands",
  pages        = "78--85",
  year         = "2010",
  editor       = "Kielmann,T. and van Kreveld,M.J.",
  url          = "http://graphics.tudelft.nl/Publications-new/2010/POBGHV10"
}