Count nuclei in a low contrast microscope image

Hello!

I was given the task to count nuclei in low contrast microscope images. The nuclei are barely visible by eye and I have to count them in over 600 images. It would be great to automate this task at least by a bit.

The images look like this one:

I have to count the “light” ovals. I marked three examples in the folowing image:

I played a bit with the filters I know from my digital image processing course and used the unsharp mask filter to achieve some good results. The next image shows the original image filtered by unsharp mask filter with 5px radius and 0.9 mask weight.

I’m currently stuck here. Do you have any ideas how to

  1. seperate the nuclei even more from the rest of the image
  2. mark and count the nuclei in this picture

I’m happy for every suggestion you might have.

Thanks in advance
Georg