FREE MRSO Magnetic and RF Shielding Concepts Questions and Answers

Question 1

What is the primary function of the Faraday cage constructed around an MRI scan room?

Accepted Answer

To prevent external radiofrequency interference from corrupting images.

Answer

To contain the static magnetic fringe field.

Answer

To provide acoustic dampening from the gradient coils.

Answer

To protect against cryogen leaks in the event of a quench.

Question 2

How does active magnetic shielding reduce the fringe field of an MRI scanner?

Accepted Answer

By using a set of secondary superconducting coils with an opposing current.

Answer

By surrounding the magnet with thick plates of low-carbon steel.

Answer

By lining the scan room walls with copper sheeting.

Answer

By generating a high-frequency radio wave to nullify the static field.

Question 3

A persistent 'zipper' artifact appearing in the center of images across multiple sequences and patients is most likely caused by what?

Accepted Answer

A breach in the radiofrequency (RF) shield.

Answer

A failure in the passive magnetic shielding.

Answer

A quench of the superconducting magnet.

Answer

Malfunctioning gradient coils.

Question 4

What is the primary material used for passive magnetic shielding?

Accepted Answer

Low-carbon steel

Answer

Copper

Answer

Lead

Answer

Aluminum

Question 5

The main goal of magnetic field shielding is to contain which specific field strength line within a controlled area?

Accepted Answer

5 Gauss (0.5 mT)

Answer

1 Gauss (0.1 mT)

Answer

50 Gauss (5.0 mT)

Answer

100 Gauss (10.0 mT)

Question 6

What is the principle behind using a waveguide for penetrations through an RF shield?

Accepted Answer

It acts as a high-pass filter, attenuating frequencies in the MRI operational range.

Answer

It uses magnetic induction to cancel RF waves.

Answer

It is filled with a dielectric gel that absorbs RF energy.

Answer

It is made of a non-conductive material to insulate the opening.