MRI MRI Safety

Question 1

Which MRI zone is defined as the area containing the MRI scanner itself where the static magnetic field is always present?

Accepted Answer

Zone IV

Answer

Zone IV is the MRI scanner room where the magnet is always on and unrestricted ferromagnetic items pose immediate danger.

Question 2

A patient reports having a cardiac pacemaker. What is the standard MRI safety classification for most older pacemakers?

Accepted Answer

MR Unsafe

Answer

Most older pacemakers are classified MR Unsafe because the magnetic field can interfere with device function or cause heating.

Question 3

What is the main biological risk associated with rapidly switching gradient magnetic fields during an MRI scan?

Accepted Answer

Peripheral nerve stimulation

Answer

Rapidly switching gradients can induce electrical currents in body tissue, causing peripheral nerve stimulation (PNS).

Question 4

Which SAR limit (Specific Absorption Rate) is the FDA guideline for whole-body RF energy deposition in a 15-minute period for non-controlled conditions?

Accepted Answer

4 W/kg

Answer

The FDA guideline for whole-body average SAR under normal operating mode is 4 W/kg over any 15-minute period.

Question 5

A patient with a metallic foreign body in the eye should be evaluated with which imaging modality BEFORE entering the MRI suite?

Accepted Answer

CT scan

Answer

A CT scan of the orbits is used to detect metallic ocular foreign bodies before MRI because ferromagnetic metal near the eye is a contraindication.

MRI - Magnetic Resonance Imaging Practice Test

MRI - Magnetic Resonance Imaging Practice Test

MRI MRI Safety