Rufus's comments

BTW: A few companies that make MR spectrometers for laboratory research sell 900 MHz systems, which are = 21 Tesla (and change).

People MRI's are a whole lot weaker than many research magnets out there, today.

The dueling speculation with regard to how close (or far) you need to be from an MRI scanner ignores a few points. First, the attractive (translational) effect is not strictly a result of the strength of the magnet, it is a product of the magnet strength and the magnetic spatial gradient (or, by analogy, the 'steepness' of the magnetic field).

Contemporary MRI scanners use what's referred to as 'active magnetic shielding' which means that the magnetic field is 'girdled' and held closer to the scanner than it would be if we just let it follow the cube-of-the-distance drop-off rate. This increases the 'steepness' of the magnetic field, but pulls it closer to the body of the instrument.

One of the major factors regarding attractive force is the object that is being pulled. The longer it is (not so much the 'bigness' but the length), the greater the potential pull. The attractive force is a result of the difference between the magnetic field as experienced by one end of an object and the field at the other end. The greater the difference (a product of the steepness of the field and length of the object), the stronger the attractive force.

So, theoretically you could take a 2D ferromagnetic filament and, if you turned it so that it didn't cross any of the magnetic flux lines, the attractive force would = 0. Keeping the center in the same location but rotating the filament so that it crossed flux lines, presto, attractive force!

If you're looking for more information about magnetic projectile accidents, I suggest you check out http://mrimetaldetector.com/blog/2010/02/mri-projectile-acci... and the other posts.