Magnetic resonance imaging is probably one of the hardest subjects to understand in radiology physics, probably because most of the concepts are oversimplified, in the same way that in A-level chemistry you learnt that your GCSE chemistry, whilst a good approximation to the truth, is oversimplified.
If you want to get to the "truth", then http://www.revisemri.com is a good start. However, I'll be focusing on what you need to pass the exam.
The first section of this chapter covers a little on the MR machine and the various magnets and coils as this will make it easier to understand the axes and how the transverse magnetisation is produced. Then the "Introduction to MRI" is a chapter on the basic physics of MR needed to understand everything else. I've subsequently separated out the pages based on the way I found it easiest to work through and understand i.e. I haven't included all the sequences in one chapter.
- 1. MR machine
2. Introduction to MRI
3. T1 and T2 signal
4. Spin echo sequence
5. T1, T2 and PD weighted imaging
6. Spatial encoding
7. Slice selection
8. Frequency encoding
9. Phase encoding
12. Spin echo sequences - Detailed
13. Gradient (recalled) echo sequence
14. Inversion recovery sequences
15. MR angiography
16. MR contrast agents
17. MR image quality
18. MR artefacts
19. MR safety
There are many different books out there on MRI imaging. No individual book is 'best' as it largely depends on your individual learning style. Having said that, MRI in Practice is excellent as it's simple to follow and easy to understand, taking you step-by-step through MRI. If you have this book, you'll be fine in the physics exam! For a comprehensive list of recommended physics books, courses and online resources, take a look at the Radiology Cafe First FRCR exam hints and tips page.
MRI in Practice
Catherine Westbrook, Carolyn Roth, John Talbot
For further clarification there are many online and paper sources of information.