Paint with round brush

Hi, I have to segment a laryngeal tumor, but the paint function doesnt work on the tumor tissue, in other words, it doesnt recognize the tissue? Is there a better tool for tumor segmentation in that area?
Thank you

Tumors can often be quickly and accurately segmented using Grow from seeds effect. Just paint a scribble inside and outside the tumor in two orthogonal slices and click Initialize to see a preview. Then review and make corrections as needed (by drawing additional scribbles).