how to read static magnetic field map - Answer move further from bore -->
magnetostatic lines are spaced further out
higher static magnetic field --> can experience __(more/less)___ torque - Answer MORE
Cryogens: 3 effects? - Answer explosions
asphyxiations
frostbite
Cryogen explosions - Answer occur when pressure release valve malfunctions
regular air can get in container; water vapor can freeze solid over valves --> causes
pressure buildup
Cryogen asphyxiation - Answer cryogens escaping into scanner room can CROWD out
oxygen
--> rapid breathing, impaired coordination, impaired alertness, depression of senses
, Cryogen frostbite - Answer =cold burns
can cause tissue damage, lung damage if inhaled, change of skin color, blistering
how to stay safe with cryogens - Answer oxygen monitor, quench vents, hammer, door
open outward, kick-out panels;
check quench vents, quench drills, cryogen level monitoring
How does RF heating happen? - Answer magnetic field component of an RF wave is
what we blame for RF heating, not electric field component.
but...
electric fields in body induces currents...
resistance to electric flow deposits heat...
***
--> a changing magnetic field (such as that in a RF wave) induces an electric current. this
electric current can cause heating and other disturbances (nerve stimulation, etc.)
B1 - Answer time-varying RF fields... RF power...
near-field effect - Answer (a mechanism for RF heating)
"contact" with RF coil/antenna
near field = region where there are strong effects from currents/charges in the antenna
that cause electromagnetic components that don't behave like far-field radiation
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