Imaging for Physicists

Fringe (stray) Field

• Scanner ‘footprint’

> 30 G Stainless steel, non- ferromagnetic objects < 30 G ECG monitors, unrestrained ferromagnetic objects < 10 G Credit cards, x-ray tubes

Credit cards erased at 10 G Safety limit is ‘five gauss line’ • 7 Tesla scanner has 23 m 5 G line Passive & Active shielding • Radial & axial components Typically axial 1.6 times larger • May be measured with handheld gaussmeter

< 5 G

Pacemakers, general public

< 3 G

Moving cars etc

< 1 G

TVs, CT & PET scanners

< 0.5 G Railways, gamma cameras