Finding faint lines in images

Hi,

I'm trying to find the faint line that goes through the middle of the seed in this image - you can see what looks like a faint Gaussian curve which is in the bottom 3rd of the image.

I've tried all sorts of techniques but because of the brightness of the other pixels, they aren't picking them up.

My goal is to separate these parts to measure them both independently in terms of volume.

Many thanks for any help!