Comment by azan_

Both. 1.5/3 T is standard, >3 T machines (such as 5 T from United Imaging) are becoming more popular (and affordable) and at the same time ultra low field ones keep improving and now they make some things that were impossible before now actually doable such as bed-side MRI (not in clinical practice of course, but there was nice engineering proof of concept with ultra low field MRI machine that could be powered by normal power outlet).