Thursday, July 26, 2007

CFD in Coronay Arteries: Part 1

For the past few weeks, I've been trying to develop a software that will be able to quantify the vulnerability of a plaque to rupture. As I mentioned before, no software in the market today is capable of extracting such information from CTA - this is my motivation. Nevertheless, no matter how motivated I am, it is not possible for me to develop such a software in a month; this is far beyond my capabilities. As a result, I broke the project up into four parts: Part 1, segment the lumen of the coronary arteries using CTA data; Part 2, discretize the boundaries into small cells to form a volume mesh or grid; Part 3, apply Navier-Stokes equations to solve the equations of motion; and finally, Part 4, validate simulation and develop a turbulence index to quantify the vulnerability of a particular lesion or plaque.

Part 1: Segmentation

Thus far, I've only been able to complete part 1 (figure). Basically, I have created an interface that allows one to load CTA data, preprocess the data through numerous filters, and finally, segment the arteries of interest using a region growing algorithm and/or simple thresholding. The software is far from perfect since it performs the segmenation in 2D. That is, it segments the arteries slice by slice, causing the whole process of segmentation to be slightly tedious. Nevertheless, one can use it to reconstruct arteries of interest.

Part 2: Tessellation

Pending... I'm trying to tessellate the segmented volume with rectangles. The following depicts the grid for a straight pipe. Although it seems simple, it is really not for odd geometries.

Part 3: Computational Fluid Dynamics

If I get lazy, which I probably will, I plan to use a CFD software package like FLUENT. This sophisticated software package will allow me to simulate blood flow in reconstructed arteries of interest. The following is a simulation by some company (I can't find there link so if anyone knows where this is from, post it in the comments).

Part 4: Validation and Index Development

I will validate the simulation by comparing theoretical fractional flow reserve values to practical ones (fraction of pressure about a lesion). And if the simulation proves to be incorrect, I will change the parameters of the mesh; otherwise, I will work on an index that decodes vulnerability.

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