Detect the Centers for the circles

Hello ,

I have this image. I need to find the center of the four holes that is marked with Red.(InputImage.png)

I applied some image processing algorithms to preprocess the image.Then apply canny edge detection algorithm to detect the edges(CannyEdge.png).

I simplified the image so that only four holes are retained.I have marked this four holes with red line.

I used imfincircles() to find the center and radius.But as they are not circular i am not able to detect these.

   [centers, radii] = imfindcircles(bw2,[40 160],'Sensitivity',0.88,'ObjectPolarity','dark');
   %corail Trilogy
  [h,x,y]=viscircles_1(centers, radii,'EdgeColor','b');

It would be grateful if you let me know the method to find the centers for these circles.

Looking forward to hear from you at the earliest.

Thanks

Pankaja