Particle trace technique

Particle trace is the prevailing technique for visualization of intra cardiovascular blood flow. Particle trace analysis will include both streamlines (lines that assumes that the velocity field is stationary) and path lines (time resolved tracing).

 

Pathlines released from the four pulmonary veins, tracked through the left atria in a vortex structure and into the left ventricle.

 

Volume tracking

Current intracardiac flow visualization is based on particle trace techniques where one can follow virtual particles as they would travel through a velocity field. Limitations of this technique include potential loss of 3D depth perception, and the lack of quantification possibilities. Instead we propose a novel flow visualization technique named Volume Tracking that uses a novel mathematical representation that enables to follow volume over time. The unique advantages of Volume Tracking are:

  • Formulated as a field problem, thus results for the complete volume can be pre-calculated and the visualization can be undertaken completely interactive in real time.

  • Novel visualization by following the shape of a volume over time.

  • Novel methods for flow quantification.

  • Novel methods to study flow partitioning.

Below is an example of the application of Volume tracking given.

Volume tracking visualization of intracardiac blood flow in a healthy subject. An anatomical image in the four chamber view is displayed in the background for orientation. Labels indicate important anatomical features of the heart: the left ventricle (LV), the right ventricle (RV) the left atrium (LA), right atrium (RA) and the mitral valve (MV). Time t is counted in seconds from beginning of systole. Left: a spherical volume of blood in the left atrium near the mitral valve in early diastole. Right: The volume of blood has now moved and deformed and is ejected into the aorta. Note that the blood does not distribute evenly in the ventricle. This partitioning is clearly visualized for the first time in our studies.

Click on thumbnail below to see a movie illustrating Volume Tracking.

Click to view movie. Volume Tracking applied to a spherical volume of blood near the mitral annulus, starting from early diastole.

 

Lagrangean Coherent Structures (LCS)

 

The novel Volume Tracking mathematical formulation can also be used to identify flow compartmentalization. The image shows a 2D slice of the heart with region separators overlayed in color. Intracardiac flow compartmentalization has previously been hypothesised but this is the very first time this is visualized. The red colored ridges separates compartments of flow within in the human heart. Gamma denotes the gradient of the Volume Tracking field solution, and is dimensionless.

 

Work is ongoing as a Master of Science thesis project to calculate and visualize these LCS surfaces in three-dimensional space.

Vortex tracking

The main application have proposed a technique for pattern matching in vector fields. This technique will be used to identify and track vortex cores.

 

Click to view movie. White moving regions are regions with high similarity to a vortex core. Algorithm applied to a patient with dilated cardiomyopathy.

  
 
Click to view movie. Streamlines released from the same regions as above in the same patient.