Forming MR Images

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

Charge

Frequency

Mass

Energy level

2. If the field strength experienced by a patient within an MR magnet was increased, the precessional frequency of the magnetization of the patient's protons would be expected to:

Remain unaffected

Decreased

Increase

Reverse direction

3. _ is defined as a small change in the magnetic field along a particular axis.

A gradient

Raw data

Digital

A fourier tansform

4. If a group of protons moves toward the high end of a gradient the precessional frequency of their magnetization:

Stays the same

Increases

Decreases

Reverses directions

5. The - gradient creates a change in the magnetic field from the patient's left side to the right side
1. x
2. y
3. z

1 only

1 & 3

2 only

1 & 2

6. An image creted from a slice perpendicular to the axis running from anterior to posterior in the patient is called?

Oblique

Coronal

Transverse

Sagittal

7. In MRI, RF energy is

Transmitted to all body parts in the vicinity of the RF antenna, or coil

Collimated to strike a thin slice of protons

Shielded from striking parts of the body which are not being imaged

Focussed at a specific section of the patient's body

8. In order to disturb the protons in a particular location of the body, the frequency of the transmitted RF energy must be:

42.7MHz

Matched to the precessional frequency of the magnetization of protons at that particular location

63.5 MHz

9. If the slice though the patient that we wish to image is in a magnetic field of 0.995 T, the RF energy sould be transmitted at _ MHz.

42.85

63.9

42.39

42.6

10. Which of the following is the function of the gradients?

They are responsible for ensuring that all of the protons in the body simultaneously receive the RF energy

They provide the energy used to move the net magnetization of the protons into the transverse plane

They casue the precessional frequency to vary with position

They stabilize the magnetic field

11. If a patient is placed in a perfectly homogeneous 1.0 T MR system in the absence of a gradient magnetic field, and an RF pulse was transmitted at 43 MHz, _ would absorbe the RF energy.

Only the protons near the patient's head

Only protons on the patient's left side

Only protons in th ecenter of the magnet

None of the protons

12. The _ gradient will make the precessional frequency of the magnetization of protons in the patient's right eye different than that of the left heel.
1. x
2. y
3. z

1&3

1 &2

1, 2, & 3

2 & 3

Forming Mr Images