How to perform alignment of images so that the major vessels are in the same direction?

[Anirudh Thatipelli]

I am a beginner in image processing and I am working on a medical image processing project. I want to localize the major vessels in the image given below and rotate the images if the major vessels are in a different direction.

If my input image is:

Then the major vessel is the blue line marked in the image below:

If the image is:

The major vessels here will be:

How can I do this? The major vessels are mostly the vessels with the highest intensity.