  Volumetric change in glioblastoma multiforme (GBM) over time is a critical
factor in treatment decisions. Typically, the tumor volume is computed on a
slice-by-slice basis using MRI scans obtained at regular intervals. (3D)Slicer
- a free platform for biomedical research - provides an alternative to this
manual slice-by-slice segmentation process, which is significantly faster and
requires less user interaction. In this study, 4 physicians segmented GBMs in
10 patients, once using the competitive region-growing based GrowCut
segmentation module of Slicer, and once purely by drawing boundaries completely
manually on a slice-by-slice basis. Furthermore, we provide a variability
analysis for three physicians for 12 GBMs. The time required for GrowCut
segmentation was on an average 61% of the time required for a pure manual
segmentation. A comparison of Slicer-based segmentation with manual
slice-by-slice segmentation resulted in a Dice Similarity Coefficient of 88.43
+/- 5.23% and a Hausdorff Distance of 2.32 +/- 5.23 mm.
