I have a goal of measuring muscle volume on MRI images, I have spent time on 3d slicer programme, but I would try itk, are they similar which one is the best?
Both ITK and Slicer could probably help you to achieve your goal. Actually Slicer uses ITK to process images. You don’t have to choose one or the other, you could use both. I think the first question you want to answer is whether or not you want or need a user interface. If you need a UI, you can use Slicer for that. You can use ITK for the algorithm part of your tool.