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Flashcards in Gradient coils Deck (30)
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1

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

Time varying magnetic fields (gradient)

2

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

Oscillating magnetic fields (radiofrequency

3

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

Horizontal

4

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

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

 

5

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

X gradient

6

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

Y gradient

7

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

Z gradient

8

The primary biological effect of radiofrequency fields is

Tissue heating

9

The measurement of radiofrequency absorption is delineated as:

Watts per kilogram

10

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

Warmth and/or increase in body temperature

11

Current FDA limits on time varying magnetic fields are

Once the patient experiences peripheral nerve stimulation

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

EPI

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

A and D

14

The gradient rise time is defined as the:

Time it takes for the gradient to reach its full amplitude

15

The gradient slew rate is the

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

 

16

The duty cycle is defined as the:

Time the gradients are on during a TR period

17

RF (radiofrequency) energy is:

Low energy non-ionizing radiation

18

Magnetic field inhomogeneity is expressed in:

Parts per million

19

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

: Parallel imaging

 

20

Cables from RF coils and gating/trigger leads should be

Braided and positioned straight in the bore

21

RF heating is more of a concern in ________ sequences.

Fast spin echo

22

Applying two gradients simultaneously during slice selection would

Produce an oblique slice

23

Multiple coil elements combined with multiple receiver channels make a:

Phased array coil

24

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

Slew rate

25

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

Signal loss

26

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

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

27

A 6 inch surface coil is able to receive signal:

3 inches deep into the patient

28

When going from a linear coil to a quadrature coil

SNR is increased by 40%

29

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

Slew rate

30

Utilization of surface coils yields all of the following EXCEPT

Increased FOV capabilty