Highlight areas with different colour that the area that surround them
I've just started with Computer Vision and also with OpenCV.
I'm working with MRI brain images and I wondering if there is a filter or something that let me segment the areas that I haver marked with red on this image:
The original image is this one:
Yes, I know that there are a lot of deep learning solutions to segment this kind of networks, but I'm wondering, because I'm newbie, if there is a filter to highlight these areas that I have surrounded.