How can the geometric centre of the hole in the centre of a yellow object in a photo be found in a robust way?

Details:
I am a rookie to CV and trying to use a machine vision algorithm to find the center through-hole at the front of the yellow neuron electrode in the picture(as photo show). I tested some matlab algorithms but its not working well, the process involves converting to grayscale first, then edge detection, then morphological operations. It seems that I shouldn’t think this way.

Expecting: I’ve provided nearly 10 electrode images (captured from different angles and with varying degrees of clarity). I sincerely hope that someone can attempt to solve this problem, whether using traditional computer vision algorithms or neural networks—either approach is acceptable.

Google Drive containing photos

Can anyone help? I really want to figure it out. :smiling_face_with_tear: