MRI MRI Safety 5

Question 1

During a magnet quench, what is the main danger to people in the scan room if the quench pipe fails?

Accepted Answer

Asphyxiation and cryogenic burns from helium gas

Answer

Boiling helium can displace oxygen and cause frostbite, so the room should be evacuated at once.

Question 2

Rapidly switching gradient fields (dB/dt) most directly cause which effect?

Accepted Answer

Peripheral nerve stimulation

Answer

Fast-changing gradient fields induce currents in tissue that can stimulate peripheral nerves and cause tingling or twitching.

Question 3

Which patient has the highest risk of nephrogenic systemic fibrosis after receiving gadolinium?

Accepted Answer

eGFR below 30 mL/min/1.73 m² or on dialysis

Answer

NSF risk is mainly in severe chronic kidney disease or acute kidney injury, especially with higher-risk (group I) agents.

Question 4

What is the FDA guideline limit for peak unweighted sound pressure level in MRI?

Accepted Answer

140 dB

Answer

FDA guidance sets the peak unweighted sound pressure limit at 140 dB, and hearing protection is required for all patients.

Question 5

A patient has a medication patch with a metallic foil backing. What is the main safety concern?

Accepted Answer

RF heating that can burn the skin

Answer

Metallic backing can heat during RF transmission, so these patches are usually removed before scanning with the prescriber's approval.

MRI - Magnetic Resonance Imaging Practice Test