VSLUNG

vslung - Automated Lung Segmentation of Pulmonary CT scans

vslung [-H] [if=<inputfile>] [ig=<mapfile>] [ol=<outputfile>] [or=<outputfile>] [car=<carina>] [-d] [-v] [-w]

vslung automatically segments the lungs from a pulmonary CT scan. The input is a full lung scan (if=), a map with segmented airways (ig=) and carina location (x,y,z) (car=). The output is the segmented left (ol=) and right (or=) lungs. The following steps are used:

1. Median filter on the first one fourth of the image (vmedian xy=4) and combine
the filtered frames with the rest.

2. Spatial filter on the outcome from 1 (vsf k= (x=1,y=3, tf=0.33).

3. Threshold the outcome from 2 at -250HU.

4. Remove dilated airway (vmorph -d s=9,9,1).

5. Erode outcome from 3 to remove small isolated regions (vmorph s=5,5,1 -e).

6. Remove nodata region.

7. Select two lungs: carinax+70mm is the left lung, carinax-50mm is the right lung. (vssel is used, it is similar as v3sc but is able to find the closest non-zero pixel if seed point is zero). Both lung regions have to be at least of 1000 voxels to avoid selecting small isolated regions.

8. If two lung regions have different volumes, go to the next step. Otherwise perform partition using vlpart (the cutting plane is added back to left lung).

9. Dilate the two lung regions using (vmorph -d s=5,5,1) to get the eroded region back (see step4). Then perform vessel closing (vmorph -de s=20,20,5).

10. Check lung segmentation quality:

(1) If either lung volume < minimum (500cm^3), go back to step 3 with a new threshold of -200HU (not validated);

(2) If either lung volume > maximum (6000cm^3), go back to step 3 with a new threshold of -450HU (not validated).

(3) If left/right vol<=0.4 or left/right vol<=0.4, consider outcome incorrect.

(4) Else all conditions passed and proceed to next step.

11. If (4) is true in step 10, write out the two lung regions. If (1) or (2) is true, use a new threshold to perform segmentation again. If the new threshold still fails, delete temporary files and exit the program. If (3) is true, delete temporary files and exit the program.

Y. Xie