PRACTICE QUESTIONS FROM CLASS

Question 1

1. What are the two theories used to describe the basic prinicples of MRI?

Answer 1

Classical Theory and Quantum Theory

Question 2

2. What is the Lamor equation and describe each parameter of this equation?

Answer 2

It is used to measure the precessional frequency using the strength of the magnetic field and the gyro-magnetic constant of hydrogen.

Question 3

4. What is free induction decay?

Answer 3

As T2 decay occurs, there is a decrease in the signal produced and this is the FID (induction of reduced signal)

Question 4

5. What are the MRI weightings used?

Answer 4

T1, T2 and Proton Density

Question 5

6. Why is imaging contrast needed?

Answer 5

To show pathologies and differentiate between different anatomy structures

Question 6

7. Name two categories that diagnostic imaging contrast usually depends on.

Answer 6

Intrinsic and Extrinsic (Can change ext)

Question 7

8. A spin echo T1 weighted sequence uses a ____ TR and ____ TE.

Answer 7

8. A spin echo T1 weighted sequence uses a short TR and short TE.

Question 8

A T2 weighted image has a____ TR and a ____ TE

Answer 8

A T2 weighted image has a long TR and a long TE

Question 9

A proton density has a ___ TR and a ____ TE

Answer 9

A proton density has a long TR and a short TE

Question 10

9. Name a disadvantage of a GRE (Gradient Echo) MRI sequence?

Answer 10

It is very susceptible to any metal as there is no compensation for the field inhomogeneities.

Question 11

10. What are three types of magnets?

Answer 11

Permanent magnets, super conducting (what we use) and electromagnets

Question 12

12. Name the three types of magnetisim

Answer 12

iamagnetism, ferromagnetism, paramagnetism

Question 13

13. Three motions of an atom?

Answer 13

Nucleus spins on axis, electrons spin on own axis, electrons orbit nucleus

Question 14

14. What does the the yellow triangle with MR on it mean?

Answer 14

MRI conditional – can take into room and around magnet then can under certain conditions stated.

Question 15

15. Give any four tips for dealing with claustrophobic patients?

Answer 15

Feet first, support person, can perform some prone, do not strap down, worst case scenario = GA, give breaks, give a mirror / fan

Question 16

17. What is phase mismapping artefact also known as?

Answer 16

Ghosting or blurring artefact

Question 17

18. What is the artefact called seen on the outer edges of the this abdominal Fiesta MRI coronal image?

Answer 17

Moire artefact

Question 18

19. Which two cranial nerves are seen when imaging the IAMs?

Answer 18

Vestibulocochlear and facial nerve (VII and VIII)

Question 19

20. What is the Magic angle artefact?

Answer 19

An artefact seen in certain tendons – going to get a high signal artefact that is not real. Can see this in the knee with the patellar tendon and under the shoulder. May mimic pathology and is caused when certain structures with tightly bound fibers lie at an angle of 55 degrees to the main magnetic field, altering its signal intensity.

Question 20

21. Explain the difference between cross talk and cross excitation?

Answer 20

Cross excitation: energy given to nuclei in adjacent slices by RF
Cross talk: energy given to adjacent slices due to spin lattice relaxation. Cannot do anything about this.

Question 21

23. What do the arteries of the brain COW stand for?

Answer 21

Circle of Willis

Question 22

24. What would you do to reduce peristalses in an abdominal MRI?

Answer 22

Buscopan. Anterior sat band can be prescribed also (but probably not for an abdomen) and get them to hold their breath.

Question 23

26. Why is the use of pre-saturation bands important to use when imaging the C-spine?

Answer 23

To cut out swallowing and pulse of carotid arteries

Question 24

27. What sort of an RF pulse does a spin echo use to eliminate the effects of inhomogeneities?

Answer 24

180 pulse

Question 25

28. Name two advantages of a Spin Echo Sequence.

Answer 25

Good image quality, versatile, true T2 weighting, available on all systems, gold standard for image contrast and weighting

Question 26

29. What are a pixel and a voxel?

Answer 26

Pixel: picture element Voxel: Volume element

Question 27

30. Name any two factors T1 and T2 relaxation depends on.

Answer 27

Inherent energy of tissue, how close molecules are packed, how much molecules tumbling rate matches Larmor frequency

Question 28

31. Family members and additional personnel accompanying the patient into the scan room:

Answer 28

Should be screened as if they are going through MRI procedure themselves

Question 29

32. In preparation of the MRI exam patients are encouraged to?

Answer 29

Either arrive at MRI centre wearing a tracksuit without any metal zips or studs or change into a hospital gown.

Question 30

33. Is it good practice for all MRI patients that undergo MRI to be monitored?

Answer 30

Visually and verbally

Question 31

35. When using MRI cables from RF coils and ECG leads should be?

Answer 31

Placed straight, without touching the patient or the magnet bore, through the imager.

Question 32

36. Magnetic field shielding can be achieved either actively or passively. In order to achieve passive shielding, the room can be lined with:

Answer 32

Steel

Question 33

37. RF shielding can be achieved by lining the MRI room with:

Answer 33

Copper

Question 34

38. A quench is used to:

Answer 34

Rapidly removed the superconductivity and the magnetic field.

Question 35

39. The purpose of shimming the magnet is to:

Answer 35

Make the B0 field as homogenous as possible

Question 36

40. The term used to describe RF absorbtion is:

Answer 36

Specific absorbtion rate

Question 37

42. Aliasing (wrap around) occurs because the tissue outside the FOV is:

Answer 37

Undersampled

Question 38

43. To eliminate chemical shift artefact use:

Answer 38

Chemical saturation

Question 39

44. It is the ability to distinguish between two points as separate and distinct and is controlled by voxel size:

Answer 39

Spatial resolution

Question 40

45. T2 relaxation time is defined as when

Answer 40

63% of the transverse magnetisation has decayed

Question 41

46. Hydrogen nuclei have a magnetic moment because they possess a property called:

Answer 41

Spin

Question 42

47. The liquid cryogen is commonly used to maintain the magnet at superconducting temperatures is:

Answer 42

Helium

Question 43

48. In a spin echo sequence the time between the 90 degree pulse and the peak of the signal is the

Answer 43

TE

Question 44

49. This sequence is often used in MS imaging to demonstrate plaques

Answer 44

FLAIR

Question 45

50. An inversion recovery spin echo sequence begins with a

Answer 45

180