FREE MRSO Radiofrequency Field Bioeffects Questions and Answers

Question 1

A patient with a large, dark tattoo on their upper back undergoes an MRI.
Midway through the scan, they report a significant, localized heating sensation over the tattooed area.
Which RF-related bioeffect is the MOST likely cause of this thermal sensation?

Accepted Answer

Direct RF energy absorption by ferromagnetic metallic compounds in the tattoo ink.

Answer

The antenna effect, where the tattoo's conductive pigments resonate at the Larmor frequency.

Answer

Increased local SAR due to high water content in the tattoo ink.

Answer

Gradient-induced eddy currents concentrating in the dermis layer.

Question 2

According to IEC 60601-2-33, what is the whole-body averaged Specific Absorption Rate (SAR) limit for the 'Normal Operating Mode'?

Accepted Answer

2.0 W/kg

Answer

0.4 W/kg

Answer

4.0 W/kg

Answer

8.0 W/kg

Question 3

An MR technologist is preparing a patient with an external, wired monitoring device (e.g., an ECG). To minimize the risk of RF-induced thermal injury from the 'antenna effect', which action is most critical?

Accepted Answer

Preventing the wire from forming conductive loops and keeping it from touching the patient's skin directly.

Answer

Placing thermal insulation between the wire and the patient's skin.

Answer

Ensuring the wire is laid straight, parallel to the main magnetic field (B0).

Answer

Positioning the wire as close to the isocenter as possible.

Question 4

Which of the following scan parameters, when doubled, would lead to a four-fold increase in the Specific Absorption Rate (SAR)?

Accepted Answer

Transmit RF pulse flip angle

Answer

Repetition Time (TR)

Answer

Echo Time (TE)

Answer

Number of slices

Question 5

A researcher proposes a study using an investigational pulse sequence that will operate the scanner in the 'First Level Controlled Operating Mode'. According to IEC guidelines, what is the primary requirement for operating in this mode?

Accepted Answer

The operator must acknowledge the mode, and the patient requires medical supervision.

Answer

The patient must be sedated for the duration of the scan.

Answer

The scan must be performed on a scanner with a field strength of 1.5T or less.

Answer

A physicist must be physically present in the control room during the scan.

Question 6

Some individuals report hearing clicks, pops, or buzzing sounds during MRI scans that are distinct from the loud acoustic noise of the gradients. This phenomenon, known as the microwave auditory effect or RF hearing, is caused by:

Accepted Answer

Thermoelastic expansion of soft tissues in the head absorbing RF pulses.

Answer

Vibration of the RF transmit coil interacting with the gradient fields.

Answer

Magnetostriction of the patient's dental fillings or metallic implants.

Answer

Direct stimulation of the auditory nerve by the radiofrequency field.