how to measuring curve line of an image

i have to measure pixel lenght of A, B, and C line such as in 'ukuran sapi' image. i got the A and C lenght using imdistline. but the B line is curve line so i can't use imdistline. i wonder if using imellips will work. </matlabcentral/answers/uploaded_files/25281/ukuran%20sapi.jpg>

this '14 p'munif' image is an image that i got after segmentasi process using grow cut </matlabcentral/answers/uploaded_files/25280/14%20p'munif.JPG>

thank you