MRSO - Static Field - Module 2 Exam Questions With Correct Answers
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Course
MRSO
Institution
MRSO
MRSO - Static Field - Module 2 Exam
Questions With Correct Answers
Static field metrics - answer1T = 10,000G
(0.5mT = 5G)
Who published guidelines titled "Criteria for Significant Risk" that specifies what qualifies as
significant risk of exposure to magnetic field associated with MRI. - answe...
MRSO - Static Field - Module 2 Exam
Questions With Correct Answers
Static field metrics - answer✔✔1T = 10,000G
(0.5mT = 5G)
Who published guidelines titled "Criteria for Significant Risk" that specifies what qualifies as
significant risk of exposure to magnetic field associated with MRI. - answer✔✔FDA
FDA guidelines state EXPOSURE to a static field that does not pose a significant risk is: -
answer✔✔Limited to 8T for adults and infants > 1 month
Limited to 4T for infants < 1 month
Forces related to static field - answer✔✔-Torque/rotation
-Translation/Displacement
-Lenz
magnetic saturation - answer✔✔The point where an increase in magnetic force produces no
further magnetic effect in a magnetic material. .
magnetic saturation depends on: - answer✔✔-material
-size and shape
-temperature
Most ferromagnetic items are going to saturate at: - answer✔✔0.3T - 2.2T
Torque - answer✔✔force exerted on elongated ferromagnetic object so it aligns with the
direction of the magnetic field
Torque will cause an item to align in the _____________ axis in a horizontal field magnet. -
answer✔✔z
Torque will cause an item to align in the _____________ axis in a vertical field magnet. -
answer✔✔y
Torque is dependent on: - answer✔✔-length (longer=greater)
-shape (elongated>sperical)
-texture (soft/flexible<hard)(leads/wires<plate)
-location in magnet (greatest at isocenter)
Torque is greatest at - answer✔✔isocenter
Translational / Displacement (missile effect) - answer✔✔attractive force on a ferromagnetic
object in a spatial gradient magnetic field
Translational force increases when - answer✔✔the field change over distance increases (dB/dx)
Spatial gradient magnetic fields are expressed in - answer✔✔T/m or G/cm
(1 T/m = 100 G/cm)
Displacement force = - answer✔✔B0(dB/dx)
Maximum translational force is at - answer✔✔point of maximum dB/dx
At isocenter, translation force is - answer✔✔zero
Highest spatial gradient for a VERTICAL field system is at - answer✔✔pole faces
(item is more likely to attach to sides of poles rather than being drawn toward isocenter)
Where do you obtain a spatial gradient map? - answer✔✔System vendor
Highest spatial gradient for a HORIZONTAL field system is at - answer✔✔entrance to the bore
near the magnet walls
Magnetic shielding is used to - answer✔✔reshape/confine the field and bring 5G line into area of
controlled access
Related to the spatial gradient, magnetic shielding can cause - answer✔✔an increase in dB/dx
and unpredictability
Shorter bores have higher - answer✔✔dB/dx at bore entrance
Lenz's Law - answer✔✔The induced electromagnetic force (emf) gives rise to a current that
flows in a direction so as to set up a magnetic field to oppose the change in magnetic flux
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