your can go for segmentation techniques to target ROI what will do your task , there are so many manual and automatic segmentation techniques like morphological and k- means, level set etc you can refer to my papers published for tumor detection and segmentation  also

I want to extract white patches. I have tried thresholding, k-means and morphological operations, but do not work on all images. Is there any method to identify and extract WHITE PATCHES?

then go for adaptive or hybrid segmentation techniques , and yes morphological operations are best for manual ROI detection may be you are not using them up to there maximum potential

Thank you

Roopa,

Would it be okay to down load the image examples you show in your question and do some image analyses and enhancements in an attempt to extract some of the information that is of interest ? 

Pat

Hello,

We have not used online data.

Google about NCI/NIH database