How can I make the active contour work more efficiently?

Hi.

As you can see from the image I attach I am trying to segment the image, using a Local Gaussian Distribution algorithm active contour.

No matter, what configurations I tried, I also adjusted the contrast of the image and changed the cropping window up and down, still it won't segment correctly.

Correct segmentation, should be, if the red contour overlap the middle spike on the image and ecapsulate it but NOT cross OVER it as now it does.

How can I modify the contour so it encloses the whole white area of the middle spike as a cap and NOT cross through it.

Any ideas?

Thank you