Tube Geometry - Display/Calculate Centroid

At the bottom left of the TGA: Define Centroid panel a message appears prompting the user to "choose 1st anchor". In any of the three other canvases (transverse, sagittal, and coronal) place the mouse cursor directly over the tube where the users wants to start the tubal measurement and left click there.

At the bottom left of the TGA: Define Centroid panel a message appears prompting the user to "choose 2nd anchor". In any of the three other canvases (transverse, sagittal, and coronal) place the mouse cursor directly over the tube where the users wants to end the tubal measurement and left click there.

At the bottom left of the TGA: Define Centroid panel a message appears prompting the user to "drag anchor" in order to position the line created between the two anchors. In any of the three other canvases (transverse, sagittal, and coronal) place the mouse cursor directly over one of the ends hold down the left mouse button and drag the end so it is position near center in all three canvases trying for the best possible fit.

Now go to the TGA: Define Centroid panel to choose the final options before calculating the centroids.

Define Centroid Panel:

Centroid Algorithm Button

The centroid algorithm button brings up a new menu with three options.

Bisection

The bisection option marks a line between these two points and then generates an oblique image in the middle of the perpendicular plane and calculates the centroid using one of the three interpolation options. Next, the program generates two new line segments by using the original end points and the previous perpendicualar plane as a new end point. The process is repeated to generate the number of line segments, centroids, and obliques up to the number of iterations specified by the user.

Free Hand

The free hand option allows the user to divide the line drawn into segments and passes this information to the interpolation program (for determining the centroids).

Note: This does not work!

Import Description

The import description option allows the user to write their own equation for dividing the line into segments and pass this information to the interpolation program (for determining the centroids).

Note: This does not work!

Tube Color Min Line

The color min line is for telling the TGA programs the pixel range of the segmented tube is so the calculate program knows where to do its calculations. To change the value the user may delete and re-type in a value on the color min line remembering to hit return or use the slide bar to change the value.

Tube Color Max Line

The color max line is for telling the TGA programs the pixel range of the segmented tube is so the calculate program knows where to do its calculations. To change the value the user may delete and re-type in a value on the color max line remembering to hit return or use the slide bar to change the value.

Gen (# Obls) Button

The gen (# obls) button brings up a new menu with nine options which are 1(3), 2(7), 3(15), 4(31), 5(63), 6(127), 7(255), 8(511), and 9(1023). The first number of the given set is for telling the program how many iterations of the interpolation program to run. The second number in parenthesis of the given set is for telling the program how many oblique sections and centroids to generate for this given tube calculation.

Interpolation Button

The interpolation button brings up a new menu with three options.

Fast

The fast option is the least accurate method but produces the quickest calculations of the centroids.

Nearest Neighbor

The nearest neighbor option interpolates using the voxels closest to the segmented tube voxels and then calculates (based on the gray scale) the locations of the centroids. Note: This method is 10% to 20% slower then the fast option but more accurate.

Bilinear

The bilinear option identifies (based on the gray scale) all voxels in the plane comprising the vessel and then calculates the average vessel voxel location. Then determines the centroids.

Note: This is the preferred method. It is the slowest method but the most accurate method.

Disp During Itr Button

The display during iteration button brings up a new menu with two choices.

No

The no button does not display the intermediate changes to the various canvases.

Yes

The yes button should display the intermediate changes to the various canvases.

Note: This must be set to No at this time because if it is set to "yes" then the program will bomb out.

Calculate Button

Left click on the calculate button when ready to have the centroids found and displayed the center line in the transverse, sagittal, and coronal canvases.