Suggestions of how to improve the segmentation?

Hello

I got this segmented image (see attached), using a ChanVese contour. The problem is that after a several number of iterations the contour breaks, creating gaps in the Gaussian form (see the hill shape at the middle of the image), and also it won't go on the top of the image because of artifacts.

Can you please suggest me ways of how to improve this? I don't want the contour shape to create any gaps in the gaussian hill form, neither I want bubbles in the upper part of the image and I shall probably find a way to eliminate the white artifacts that lie at the top of the image.

Thanks