Some devices are safe to scan at lower intensities and for less time, but it's the radiologist who check on that, so not my expertise.
No, the main field is effectively permanent.
I mean, some sort of non-super-conducting MRI analogue device that the patient will have to go through.
You could find big things that way, but maybe not small things that were deep. I suspect it is hard to make something powerful enough to detect everything that might be an issue in say a 7T field, yet still safe.