FREE MRSO Radiofrequency (RF) Field Bioeffects and Specific Absorption Rate (SAR) Questions and Answers

Question 1

Specific Absorption Rate (SAR) is a measure of the:

Accepted Answer

Rate of RF energy absorption per unit mass of tissue.

Answer

Total RF power transmitted by the coil.

Answer

Peak B1 field strength in microtesla.

Answer

Change in tissue temperature per minute.

Question 2

Under the FDA's guidelines for Normal Operating Mode, what is the whole-body average SAR limit averaged over 6 minutes?

Accepted Answer

2.0 W/kg

Answer

1.5 W/kg

Answer

4.0 W/kg

Answer

8.0 W/kg

Question 3

How does SAR deposition change when the static magnetic field strength (B0) is doubled (e.g., from 1.5T to 3.0T), assuming all other sequence parameters are kept the same?

Accepted Answer

It is quadrupled.

Answer

It is halved.

Answer

It is doubled.

Answer

It remains the same.

Question 4

Scanning in the First Level Controlled Operating Mode requires which of the following?

Accepted Answer

Continuous monitoring and medical supervision.

Answer

The patient must be sedated.

Answer

Approval from the hospital's ethics committee.

Answer

Use of a scanner with a field strength of 1.5T or less.

Question 5

What is the most common cause of serious RF-related thermal injuries (burns) to patients in the MRI environment?

Accepted Answer

Formation of a conductive loop by skin contact or cables.

Answer

Exceeding the whole-body SAR limit.

Answer

Ferromagnetic materials in the patient's clothing.

Answer

Malfunction of the RF body coil.

Question 6

The term B1+rms refers to the root-mean-square of the transmitted RF magnetic field. What is its primary role in MR safety?

Accepted Answer

It is a prospective estimate used to control SAR.

Answer

It measures the strength of the static magnetic field.

Answer

It quantifies the level of acoustic noise.

Answer

It determines the likelihood of peripheral nerve stimulation.