HARDWARE QA/QC

Question 1

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 1

• RF radiofrequency coils
• gradient coils
• shim coils
• main magnet

Question 2

The gradient rise time is defined as

Answer 2

the time it takes for the gradient to reach its full amplitude

measured in microseconds — mT/m (milliTesla/meter) or G/cm(Gauss/centimeter).

Question 3

The** gradient slew rate** is

Answer 3

the speed rate of ascent or descent of a gradient from zero to its maximum amplitude, either positive or negative

Which is the amplitude divided by the rise time in msec. Measured in mT/m/msec or T/m/sec.

Question 4

The duty cycle is defined as

Answer 4

the time the gradients are on during a TR period

“gradient working time”

Question 5

Parameter changes affecting the pulse duty cycle include:

Answer 5

1. Increased # slices
2. Employment of fat suppression pulses (SPAIR requires increased TR
   compared to SPIR)
3. Utilization of presaturation slabs/bands
4. Increased ETL

Question 6

The primary cause of the noise in the MR scan room is

Answer 6

the rapid, successive switching of the gradient coils

Question 7

RF heating is more of a concern in ________ sequences due to the multiple echo train lengths, leading to potential increases in tissue heating.

Answer 7

fast spin echo

Question 8

Doubling field strength results in ____ increase in SAR potential.

Answer 8

fourfold (4x)

Question 9

The primary biological effect of radiofrequency fields is

Answer 9

tissue heating

Question 10

Consistent room temperature of ____________ and sufficient air flow in the MR scan room is recommended to make patients less vulnerable to the RF heating effects.

Answer 10

65-75°F, humidity of 50-70%

Question 11

For energy to be efficiently transferred between a transmitter and receiver, the two must be

Answer 11

at the same frequency.

Question 12

Utilization of ___________ yields a more localized, smaller FOV (field of view) capability, with increased SNR, thus providing opportunity for improved image quality on most systems.

Answer 12

surface coils (linear coils)

Question 13

A 6 inch surface coil is able to receive signal ____ inches deep into the patient

Answer 13

3

(SNR penetration depth = ½ coil diameter)

Question 14

Circularly polarized transmission or receiver coil with two orthogonal
transmission and/or receiver channels are

Answer 14

CP coil, also known as a quadrature coil

This yields better signal-to-noise than a linear coil

Question 15

When going from a linear coil to a quadrature coil, SNR is increased by

Answer 15

40%

Question 16

A ________ is comprised of multiple coil elements combined with multiple receiver channels.

Answer 16

phased array coil

Question 17

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

Answer 17

scan control room on the operator console

Question 18

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

Answer 18

scan control room at the technologist operator console

Question 19

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

Answer 19

the MR equipment room.

Question 20

The RF power amplifier is located within

Answer 20

an equipment room

Question 21

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

Answer 21

Copper

Question 22

________shielding can be accomplished by lining the MR room with steel
or other ferromagnetic plating, thus reducing the scope and distance of the fringe field.

Answer 22

Passive

Question 23

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

Answer 23

Active

Question 24

What is the magnetic field surrounding the periphery of the
MR scanner?

Answer 24

Fringe Field

Question 25

The unit of measurement of the fringe field is expressed as

Answer 25

Gauss

Question 26

FDA limit for static magnetic field in clinical use is

Answer 26

4.0 Tesla (T) field strength for all patients, but 8 Tesla for all patients over 1 month of age

Question 27

The most commonly used system in MR imaging today is the

Answer 27

Superconducting magnet

Question 28

In a superconducting magnet, the magnetic field strength is increased by

Answer 28

* increasing the turns of wire * increasing current in the wires * by reducing the spacing between the wires.

Question 29

The orientation of the main magnetic field in a high field, superconducting, short bore magnet is

Answer 29

horizontal

Question 30

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

Answer 30

4 4 Kelvin (-270° Celsius / -452° F!!)

Question 31

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

Answer 31

Helium

Question 32

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

Answer 32

* avoid asphyxiation, * frostbite, * and/or damage to tympanic membranes

Question 33

A quench refers to

Answer 33

the sudden loss of superconductivity when its temperature is raised

Question 34

All of the following are magnetic fields associated with MR imaging:

Answer 34

* Static magnetic fields * Oscillating magnetic fields (RF) * Time varying magnetic fields (gradient)

Question 35

The MRI system component that produces the magnetization of proton spins (alignment) is known as

Answer 35

the main magnet

Question 36

The MRI system component that provides the ability to perform spatial encoding is the

Answer 36

gradient system

Question 37

Side effects of the Time varying magnetic fields (gradient) have been documented as

Answer 37

* muscle contractions, * cardiac arrhythmias, * mild cutaneous sensations * visual light flashes(Magnetophosphenes)

Question 38

Side effects of the Oscillating magnetic fields (radiofrequency)

Answer 38

tissue heating

Question 39

Quality Assurance (QA) utilizes the goal of

Answer 39

maintaining a desired level of consistency and image quality requirements within Radiology

Question 40

QA (quality assurance) asks the question

Answer 40

“Are we operating the devices or equipment correctly?”

Question 41

Quality Control (QC) asks the question

Answer 41

“Is the equipment operating correctly?”

Question 42

____________is an inherent manufacturer quality mechanism by which a technologist, physicist or field service engineer might evaluate the performance of an MRI system.

Answer 42

System Performance Testing (SPT), or PIQT (Periodic Image Quality Test)

Question 43

In acquiring ACR QA data, Image 210 is used to evaluate for what quality measure?

Answer 43

High contrast spatial resolution

Question 44

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

Answer 44

ensures accuracy of Z gradient

Question 45

In acquiring ACR QA data, Image 211 is used to evaluate for what quality measure?

Answer 45

ensures accuracy of X and Y gradients

Question 46

When acquiring ACR QA data, the slice correlating to Image 213 requires what visual discernment?

Answer 46

10 visible spokes of 3 discs each

Question 47

Multiple coil elements combined with multiple receiver channels make a:

Answer 47

Phased array coil

Question 48

Magnetic field inhomogeneity is expressed in:

Answer 48

Parts per million

Question 49

When going from a linear coil to a quadrature coil:

Answer 49

SNR is increased by 40%

Question 50

The gradient rise time is defined as the:

Answer 50

Time it takes for the gradient to reach its full amplitude

Question 51

RF (radiofrequency) energy is

Answer 51

Low energy non-ionizing radiation

Question 52

Which of the following sequences would be more at risk for the effects that time varying magnetic fields can cause? A. SE. B. FSE. C. GE. D. EPI

Answer 52

D. EPI