Gradient coils

Question 1

Which of the following has been documented to cause muscle contractions, cardiac arrhythmias, mild cutaneous sensations and visual light flashes

Answer 1

Time varying magnetic fields (gradient)

Question 2

Which of the following’s primary biological effect is tissue heating/deposition

Answer 2

Oscillating magnetic fields (radiofrequency

Question 3

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

Answer 3

Horizontal

Question 4

The ____________ is responsible for the knocking noise the system makes while the sequence is in progress.

Answer 4

Rapid change/switching of the magnetic field by the gradient coils

Question 5

: If a sagittal slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient’s body

Answer 5

X gradient

Question 6

: If a coronal slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient’s body.

Answer 6

Y gradient

Question 7

: If a transverse/axial slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient’s body.

Answer 7

Z gradient

Question 8

The primary biological effect of radiofrequency fields is

Answer 8

Tissue heating

Question 9

The measurement of radiofrequency absorption is delineated as:

Answer 9

Watts per kilogram

Question 10

The effects of time varying magnetic fields can include all of the following EXCEPT:

Answer 10

Warmth and/or increase in body temperature

Question 11

Current FDA limits on time varying magnetic fields are

Answer 11

Once the patient experiences peripheral nerve stimulation

Question 12

: 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 12

EPI

Question 13

The strength of the gradient magnetic fields are measured in:

A. Gauss per centimeter
B. Tesla per echo
C. Watts per kilogram
D. Millitesla per meter
E. A and D

Answer 13

A and D

Question 14

The gradient rise time is defined as the:

Answer 14

Time it takes for the gradient to reach its full amplitude

Question 15

The gradient slew rate is the

Answer 15

Rate of speed of ascent or descent of a gradient from zero to its maximum amplitude

Question 16

The duty cycle is defined as the:

Answer 16

Time the gradients are on during a TR period

Question 17

RF (radiofrequency) energy is:

Answer 17

Low energy non-ionizing radiation

Question 18

Magnetic field inhomogeneity is expressed in:

Answer 18

Parts per million

Question 19

A technique utilized to reduce the MRI scan time which requires the use of an array

Answer 19

: Parallel imaging

Question 20

Cables from RF coils and gating/trigger leads should be

Answer 20

Braided and positioned straight in the bore

Question 21

RF heating is more of a concern in ________ sequences.

Answer 21

Fast spin echo

Question 22

Applying two gradients simultaneously during slice selection would

Answer 22

Produce an oblique slice

Question 23

Multiple coil elements combined with multiple receiver channels make a:

Answer 23

Phased array coil

Question 24

The strength of the gradient over a specific distance is known as the:

Answer 24

Slew rate

Question 25

A coil that is not properly tuned to the correct magnetic field strength will result in:

Answer 25

Signal loss

Question 26

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

Answer 26

: Radiofrequency coils, gradient coils, shim coils, main magnet

Question 27

A 6 inch surface coil is able to receive signal:

Answer 27

3 inches deep into the patient

Question 28

When going from a linear coil to a quadrature coil

Answer 28

SNR is increased by 40%

Question 29

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

Answer 29

Slew rate

Question 30

Utilization of surface coils yields all of the following EXCEPT

Answer 30

Increased FOV capabilty