Academic fair use and using publication images in your thesis
You probably have a fair use right in the US to use images from copyright-protected works without permission from the copyright holder since you are using them for a critical purpose. But, -BUT-, fair use is a defense to a copyright infringement lawsuit that is not guaranteed to be successful. If you are sued by one of the copyright holders, you will have to assert this defense to them and probably also to a judge or jury in a court of law. This may cost you (or your institution if they choose to defend you) a large sum of money to take to court. $100k would not be unheard of. Given that, unless you have this kind of money just sitting around, you would be well served by asking the copyright holders (not necessarily the article authors, more likely the article publishers) for permission to use the images. It is usually granted.