Physics 1 Quiz 4.3

Question 1

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?

Accepted Answer

42.5614 MHz

Answer

42.57 MHz

Answer

42.5785 MHz

Answer

42.5657 MHz

Question 2

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?

Accepted Answer

Phase Encoding Gradient

Answer

Slice Select Gradient

Answer

Frequency Encoding Gradient

Question 3

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?

Accepted Answer

x-y plane

Answer

none of these

Answer

y-z plane

Answer

x-z plane

Question 4

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

Accepted Answer

True

Answer

False

Question 5

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?

Accepted Answer

Z

Answer

X

Answer

Y

Question 6

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

Accepted Answer

The number of data points in each line

Answer

Receive bandwidth

Answer

Sampling time

Answer

RF transmit frequency

Question 7

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.

Accepted Answer

True

Answer

False

Question 8

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

Accepted Answer

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

Answer

As many TR periods as the number of slices

Answer

1 TR period

Answer

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

Question 9

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

Accepted Answer

True

Answer

False

Question 10

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?

Accepted Answer

Y

Answer

W

Answer

V

Answer

X

Answer

Z

Question 11

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.

Accepted Answer

True

Answer

False

Question 12

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

Accepted Answer

X

Answer

W

Answer

V

Answer

Z

Answer

Y

Answer

U

Question 13

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

Accepted Answer

Slice Select Gradient

Answer

Phase Encoding Gradient

Answer

Frequency Encoding Gradient

Question 14

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

Accepted Answer

True

Answer

False

Question 15

Which TWO factors from the following list affect slice thickness?

Accepted Answer

Slope of slice select gradient

Accepted Answer

Bandwidth of transmitted RF

Answer

The sampling interval

Answer

Power of transmitted RF

Answer

Duration of slice select gradient

Question 16

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

Accepted Answer

False

Answer

True

Question 17

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

Accepted Answer

Signal & contrast

Answer

Slice Thickness

Answer

The Center Data in the Image

Answer

Image Detail