Mammography??

I'm a recent graduate of a Radiography  program and am ARRT certified. I am interested in taking it further into Mammography. I was looking at the ARRT site and found some documents on there for Clinical Requirements. I was wondering if anyone knew this answer.

Do I only have to do clinical requirement? Or do I have to do a class also? I've heard that some people have been able to self study this field. I'm confused on where to start.

Anyone out there with some advice/answers would be great!

Thanks,

Amanda