Physics 1 Quiz 4.3

1. The sampling frequency or sampling rate is the rate at which frequencies are sampled or digitized during the acquisition window (sampling time) per second:

True

False

2. Which TWO factors from the following list affect slice thickness?

The sampling interval

Slope of slice select gradient

Power of transmitted RF

Bandwidth of transmitted RF

Duration of slice select gradient

Submit

3. Both Frequency and Phase encoding matrix sizes contribute to the scan time.

True

False

4. Which of the gradients is turned on in the middle of a sequence? In other words, which gradient is the second gradient to be turned on during a sequence?

Slice Select Gradient

Phase Encoding Gradient

Frequency Encoding Gradient

5. If the main magnetic field is aligned along the Z axis of a cartesian coordinate system, which of the following corresponds to the correct orientation of the transverse plane?

None of these

Y-z plane

X-y plane

X-z plane

6. Which physical gradient is the slice select gradient for axial slices in a brain study in a typical closed-bore, recumbent machine if the patient is positioned head-first supine?

X

Z

Y

7. In terms of the events that take place during an MRI pulse sequence, what factor determines the frequency matrix?

The number of data points in each line

Receive bandwidth

Sampling time

RF transmit frequency

8. In partial echo imaging, only the right hand side of K space is filled with data, and after extrapolation, both sides contain data and overall signal is not lost from the image.

True

False

9. To completely phase encode a single slice, how many TR periods are required:

As many TR periods as phase lines in the resulting image matrix

As many TR periods as the number of slices

1 TR period

As many TR periods as frequency steps in the resulting image matrix

10. At isocenter the magnetic field strength is always the same as B₀, even when gradients are switched on.

True

False

11. In imaging of the head, the long axis of the anatomy usually lies along the anterior posterior axis of the magnet, so which gradient performs frequency encoding?

W

V

X

Z

Y

12. Because k-space is symmetrical, we can sometimes choose to fill only a part of k-space and then calculate the remaining data instead of actually scanning it.

True

False

13. In body imaging, in axial images, the long axis of the anatomy lies along which axis of the magnet to perform frequency encoding?

W

V

Z

X

Y

U

14. The first gradient to be turned on while scanning a sequence is which?

Phase Encoding Gradient

Frequency Encoding Gradient

Slice Select Gradient

15. The information stored in the center of k-space determines what aspect of the resulting image?

Slice Thickness

The Center Data in the Image

Image Detail

Signal & contrast

16. If you apply a gradient and are at 2 cm negative to isocenter at 1T, what is the Larmor frequency of hydrogen at that location?

42.57 MHz

42.5785 MHz

42.5657 MHz

42.5614 MHz

17. In order to form a recognizable image, k-space must always be filled partially or completely in some way or another.

True

False

Physics 1 Quiz 4.3

1. The sampling frequency or sampling rate is the rate at which frequencies are sampled or digitized during the acquisition window (sampling time) per second:

2.

What first name or nickname would you like us to use?

2. Which TWO factors from the following list affect slice thickness?

3. Both Frequency and Phase encoding matrix sizes contribute to the scan time.

4. Which of the gradients is turned on in the middle of a sequence? In other words, which gradient is the second gradient to be turned on during a sequence?

5. If the main magnetic field is aligned along the Z axis of a cartesian coordinate system, which of the following corresponds to the correct orientation of the transverse plane?

6. Which physical gradient is the slice select gradient for axial slices in a brain study in a typical closed-bore, recumbent machine if the patient is positioned head-first supine?

7. In terms of the events that take place during an MRI pulse sequence, what factor determines the frequency matrix?

8. In partial echo imaging, only the right hand side of K space is filled with data, and after extrapolation, both sides contain data and overall signal is not lost from the image.

9. To completely phase encode a single slice, how many TR periods are required:

10. At isocenter the magnetic field strength is always the same as B0, even when gradients are switched on.

11. In imaging of the head, the long axis of the anatomy usually lies along the anterior posterior axis of the magnet, so which gradient performs frequency encoding?

12. Because k-space is symmetrical, we can sometimes choose to fill only a part of k-space and then calculate the remaining data instead of actually scanning it.

13. In body imaging, in axial images, the long axis of the anatomy lies along which axis of the magnet to perform frequency encoding?

14. The first gradient to be turned on while scanning a sequence is which?

15. The information stored in the center of k-space determines what aspect of the resulting image?

16. If you apply a gradient and are at 2 cm negative to isocenter at 1T, what is the Larmor frequency of hydrogen at that location?

17. In order to form a recognizable image, k-space must always be filled partially or completely in some way or another.

10. At isocenter the magnetic field strength is always the same as B₀, even when gradients are switched on.