Technical note: evaluation of a region growing algorithm for segmenting pelvic computed tomography images during radiotherapy planning.

A clinical evaluation of a computer segmentation algorithm was performed to determine whether the incorporation of such an algorithm into a radiotherapy treatment planning computer would increase the speed of segmentation and therefore increase user productivity. Six pelvic computed tomography (CT) data cubes were manually segmented akin to current radiotherapy practice on three occasions and the mean times for each data cube recorded to provide baseline measurements. The same images were then segmented using the new region growing algorithm, backed up by manual segmentation and contour editing tools where necessary, and the times compared with the baseline for each data cube. The results confirm that this algorithm can decrease segmentation times by a factor of 2.4 without compromising the quality of the final plan (p < 0.0001). Most of this time gain is from a rapid segmentation of the pelvic bones and external contour rather than the soft tissues of the pelvis. We conclude that such algorithms will be of value for segmenting large pelvic CT data cubes for radiotherapy planning by making the procedure less labour intensive.