It would be based on the images you are using, If you are going for IR images you can go for a fixed band of intensities corresponding to tumour. Or else you can rather go for split and merge operation. That should help. For any help let me know

Best regards for your project 

Thanks dude..i will try and tell you.

i think the best way of automating your code, is that you can make use of the interactive polygonal selection approach.