Segment Part of Image

I'm trying to omit a region from my grayscale image. I'm using the "Image Segmentor app" but it's not quite working the way I want it to. I want to omit the regions that appear in the white mask of the second image from the first image. (Get rid of that ring of circles but keep the remainder of the image the same). When I use the segmenter app, it gets rid of everything but the region that I segmented freehand.