@vanessab, I am not a professional, but I have learned that things like labs, blood pressure, heart rhythms and other tests are a moment in time. And by having repeated images over a period of time, there is more data to notice patterns and changes over time.
My experience as a patient at Mayo, is that if there is ever need for more tests to be added or cancelled, that they will do it, and will make ammendments to your appoints during your visit.