When you have an MRI system, one of the key ingredients to getting good data is having the magnetic field be homogenous inside the bore of the magnet (where the subject’s head is). Unfortunately elements of the local environment around the magnet (large filing cabinets for example) can adversely affect this uniformity of the field and so….when we install the MRI system, we either passively or actively counteract these effects–this is called shimming the magnet. From a passive standpoint, one can attach small metal plates to the magnet in such a way as to bring things back to uniformity. One can also actively shim the magnet, using small powered coils that produce shim current–also with the goal of making the field inside the bore perfectly uniform.
So here’s the tripper upper: once you shim an MRI, it’s really important not to move big metal objects that are within some threshold distance of the magnet. From what I’ve heard this is particularly true above the magnet, but I’ve got a lot more to learn about this.
All of this has implications for space utilization at Krasnow.
Discoverers and Discoveries 