We have had several lectures on this subject this year and I have felt more confused afterwards than when I started.  This is a subject that is very hard to teach with a powerpoint.  However, I finally feel like I have a good grasp on it now.  One of my professors suggested spending 10 minutes a day on this website: Learning Radiology.  They have a whole section of Med Student Tutorials for different types of imagining and weekly cases.  I have found it to be very helpful and would highly recommend it to anyone else who is also struggling with learning medical imaging.