Methods of image Stitching other than using feature based detection

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Hello everyone,

I have to stitch multiple images for medical cervical cancer patients. These images are the images of cells and tissues and I tried using the opencv sample executable code for stitching those but since the stitcher is not able to detect enough features in those images , it is showing an error code 1 which means that images don't have enough features to match. But that code is working perfectly for normal overlapping images. So is there any other method of stitching (other than feature based) to stitch images ?please help ...any help is highly appreciated.. Thanks very much.

I am attaching sample images also: https://drive.google.com/open?id=0B-V...

https://drive.google.com/open?id=0B-V...