detecting curves in a binary image

Hello, I have traced boundary of the image using bwboundaries(). I want to detect the infra-mammary curve and remove the part of the image below the curve. can someone help me do this?

[KALYAN ACHARJYA]

Want to keep the curves only, rest should be removed?

Carify with pointing arrow,(use paint)?

[Apoorva Maiya]

the two curves are shown in red. i want to detect the line shown in yellow so that i can segment the part below the yellow line. Thank you for replying.