VRMWALL | VisionX V4 |
vrmwall − Pleural wall removal in thresholded images
SYNOPSISvrmwall [-H] [if=<inputfile>] [of=<outputfile>] [og=<value>] [df=<value>] [ic=<value>] [d=<value>] [-p] [th=<value>] [pr=<value>] [-v] [-c] [-a]
DESCRIPTIONvrmwall segments the pleural surface from a nodule by using an iterative plane-cutting algorithm. The input image should be a 3D thresholded image with byte, short, or float pixel type. A 2D image will also work but the termination parameters will have to be changed from the defaults. There are two output images (of and og): one contains just the segmented nodule, and the other contains the segmented nodule in white and the wall and vessels in gray. A debugging file (df) can also show the segmentation after each iteration of the algorithm. For the algorithm to work, the initial location must be inside the nodule. If the center of the image is not inside the nodule, then a different initial location should be specified with the ic option.
ALGORITHMAn initial location inside the nodule is calculated as the center of the image, and an initial direction is calculated as the initial location subtracted from the center of mass surrounding the initial location. A plane, normal to the direction and passing through the location, is moved towards the pleural wall at each iteration. If the mass of the cut-nodule (the region behind the plane and contains the initial location) changes by more than some percentage, then the direction is changed to reorientate the the plane to minimize the size of the cut-nodule. If the reorientation procedure fails to lower the change enough, then the algorithm terminates and returns the cut-nodule from the previous iteration. The default termination condition is a change in difference by more than 50 percent. A different percentage termination condition or an absoulte threshold may also be specified with the pr= or th= options. The -c option forces the algorithm to always move in the same direction all the time, and the -a option uses the average difference over the iterations as the baseline for the percent termination criterion. This option may help the algorithm if the input image is very noisy.
OPTIONS|
if= |
Input Image -- thresholded 3D byte, short, or float image. (can be 2D) | ||
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of= |
Output File -- nodule segmented from pleural wall (same format as input) | ||
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og= |
Output File -- segmented nodule [white] with wall [gray] (same format as input) | ||
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df= |
Debug File -- the segmentation after each iteration of the algorithm (float image) | ||
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ic= |
x,y,z -- specify an initial location, rather than the default of the center of the image. | ||
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d= |
dx,dy,dz -- specify a initial direction of the plane, rather than the default center of mass subtracted from the initial location. | ||
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-p |
The d parameter is a point, and the initial direction is (d-ic). | ||
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th= |
Terminate when the mass difference is greater than th. | ||
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pr= |
Terminate when the difference increases by more than pr percent (default=50). | ||
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-v |
verbose option: display initial direction and location along with the density, density difference, percent change, and average density at each iteration. | ||
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-c |
Don’t change directions when reorientating the plane. | ||
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-a |
Average differences over iterations when doing percent change termination. Use this if the image is really noisy. |
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* |
Can only handle byte, float, or short images |
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SEE ALSO--
AUTHORA. B. Chan, Summer 2001