Magnetism - Hardware Control

Question 1

High field scanners typically have field strengths greater than or equal to:

Answer 1

1.5 Tesla

Question 2

Consistent room temperature of 65-75°F, humidity of 50-70%, and sufficient air flow in the MR scan room is recommended to:

Answer 2

Make patients less vulnerable to the RF heating effects

Question 3

In a cross sectional view of the MR magnet design, which coils are closest to the patient?

Answer 3

Radiofrequency coils

The RF coils are closest to the patient, leading to the primary component causing RF absorption in the patient

Question 4

The liquid cryogens are cooled in a superconducting magnet at a temperature of _________?

Answer 4

4° Kelvin

Question 5

Which of the following is NOT a magnetic field associated with MR imaging?

Answer 5

Gravitational earth magnetic fields

Question 6

The purpose of shimming the magnet is to:

Answer 6

make the B0 field as homogenous as possible

Question 7

The array processor is responsible for:

Answer 7

Reconstructing the images using the Fourier transform

The array processor is responsible for reconstructing the collected MR images/data using the Fourier transform, and is located in the MR equipment room.

Question 8

In order for energy to be efficiently transferred between a transmitter and receiver, the two must be at the same:

Answer 8

Frequency

In order for energy to be efficiently transferred between a transmitter and receiver, the two must be at the same frequency

Question 9

The _____ is located within an equipment room.

Answer 9

RF power amplifier

The RF power amplifier is located within an equipment room

Question 10

During a quench of the MR system, patients and employees should be evacuated from the scan room to avoid ______________.

Answer 10

All of the above

Question 11

Field strength at magnet isocenter is measured in units of:

Answer 11

Tesla

Field strength at magnet isocenter is measured in units of Tesla, the SI derived unit of magnetic field measurement.

Question 12

The unit of measurement of the magnetic field surrounding the periphery of the MR scanner is expressed as:

Answer 12

Gauss
The unit of measurement of the magnetic field surrounding the periphery of the MR scanner is expressed as Gauss.

Question 13

The intensity limit for a static magnetic field in clinical use is limited by the Food and Drug Administration (FDA) to _____________?

Answer 13

4 Tesla

The intensity limit for a static magnetic field in clinical use is limited by the Food and Drug Administration (FDA) to 4.0 tesla (T) strength.

Question 14

The patient image display with sequence parameter visualization is located in the _________.

Answer 14

Scan control room

The patient image display with sequence parameter visualization is located in the scan control room on the operator console.

Question 15

The local RF coil used to image a human brain is typically located/kept in the __________.

Answer 15

Magnet room

The local RF coil used to image a human brain is typically located/kept in the magnet room.

Question 16

The CPU used to plot and adjust slices in an MR sequence is located:

Answer 16

Scan control room

The CPU used to plot and adjust slices in an MR sequence is located in the scan control room at the technologist operator console.

Question 17

Radiofrequency (RF) shielding can be achieved by lining the scanner room walls with:

Answer 17

Copper

Radiofrequency (RF) shielding can be achieved by lining the scanner room walls with copper.

Question 18

The location of the coils installed in the MRI scanner, from the inner point closest to the patient to the outer most edge, are:

Answer 18

Radiofrequency coils, gradient coils, shim coils, main magnet

The location of the coils installed in the MRI scanner, from the inner point closest to the patient to the outer most edge, are: RF radiofrequency coils, gradient coils, shim coils, main magnet

Question 19

The liquid cryogens most often used to maintain field strength in a super conducting MR system are:

Answer 19

Helium

Question 20

The coil construction in an MR system, from the innermost aspect to the outer

Answer 20

Radiofrequency coils, gradient coils, shim coils, main magnet

Question 21

Doubling the magnetic field strength will:

Answer 21

Yield an increase of double the SNR

Doubling the magnetic field strength will double the SNR.

Question 22

What type of magnet is used with most systems currently manufactured?

Answer 22

Superconducting

The superconducting magnet is the most commonly used system in MR imaging today

Question 23

Passive shielding can be accomplished by lining the MR room with ___________.

Answer 23

Steel

Magnetic field shielding can be accomplished via active or passive shielding methods. Passive shielding can be accomplished by lining the MR room with steel

Question 24

Active shielding can be defined as:

Answer 24

Superconducting windings within the MR scanner, reducing the fringe magnetic field

Active shielding requires the implementation of superconducting windings within the construction of the MR scanner to oppose a portion of the magnetic field.

Question 25

_________ would be used to contain the RF in an MR magnet room

Answer 25

Copper

Copper would be installed to contain the RF in an MR magnet room.

Question 26

___________ could be used to line the walls and/or floors of the MR magnet room to reduce the fringe field, and is defined as __________ shielding.

Answer 26

Steel; passive

Question 27

Referring to SAR impact on the patient, all of the following parameter changes negatively impact pulse duty cycle EXCEPT:

Answer 27

Reduction in # slices

Question 28

Doubling field strength will result in what impact on SAR potential, if any?

Answer 28

Quadruple SAR

Question 29

In acquiring ACR QA data, Image 212 is used to evaluate for what quality measure?

Answer 29

Geometric accuracy – Z gradient

Question 30

Transmit gain is a quality measure evaluating for?

Answer 30

Accuracy of flip angles

Question 31

What is the daily/weekly QA/QC indicator testing for the accuracy of the magnetic field in determining coil tuning and consistent magnetic field strength?

Answer 31

Center frequency

Question 32

The duty cycle can be viewed as the:

Answer 32

active gradient time

The duty cycle is defined as the time the gradients are active during a TR period, the “gradient working time.”