MRI MRI Safety 4

Question 1

Under IEC normal operating mode, what is the whole-body averaged SAR limit?

Accepted Answer

2 W/kg

Answer

Normal operating mode limits whole-body SAR to 2 W/kg, while first level controlled mode allows up to 4 W/kg.

Question 2

If all other parameters stay the same, how does SAR change when a patient moves from a 1.5T to a 3T scanner?

Accepted Answer

It roughly quadruples

Answer

SAR is proportional to the square of the static field strength, so doubling B0 roughly quadruples SAR.

Question 3

Which ACR safety zone is the MR scanner room itself?

Accepted Answer

Zone IV

Answer

Zone IV is the magnet room and must be clearly marked and accessible only under direct MR personnel supervision.

Question 4

Which MR labeling symbol is a red circle with a diagonal line through it?

Accepted Answer

MR Unsafe

Answer

Under ASTM F2503, MR Unsafe items are labeled with a red circle and a diagonal slash.

Question 5

Which force on a ferromagnetic object depends most directly on the spatial field gradient, not just field strength?

Accepted Answer

Translational (projectile) force

Answer

Translational attraction depends on the spatial gradient of the static field, which is often greatest near the bore entrance.

MRI - Magnetic Resonance Imaging Practice Test