Sun28November0628PM 31

A patient presents to the radiology department for magnetic resonance imaging (MRI). Before the scan the presence of metal implants needs to be excluded.

Which of the following metals is safest within a strong magnetic field?

(Please select 1 option)

Neodymium

Cobalt

Nickel

Iron

Chromium Correct

Explanation

Ferromagnetism is the property of a substance that is attracted to a magnetic field and can be permanently magnetised. When attracted to a magnetic field a material is said to be paramagnetic. When a substance is repelled by a magnetic field it is said to be diamagnetic.

The following metals are typically ferromagnetic:

cobalt

iron

gadolinium

neodymium, and

nickel.

Gadolinium is a "rare earth" metal that is ferromagnetic below 20°C (its Curie temperature). Gadolinium-based contrast media are used to enhance MRI scans.

When placed within a magnetic field ferromagnetic materials can lead to a number of problems:

magnetic field interactions

heating, and

image artefacts.

Damage is dependent on the strength of the magnetic field, the magnetic properties of the foreign body and the geometry and dimensions of the ferromagnetic body.

The following substances are non-ferromagnetic and are therefore "MRI compatible" :

titanium

lead

chromium

copper

aluminium

silver

gold, and

tin.

Answer Statistics

1

32%

2

20%

3

16%

4

3%

5

31%

Times answered: 262