Test 2: Spatial Localization

On a sagittal image, which logical gradient is assigned to the x-gradient?

slice select

3 multiple choice options

In the standard pulse sequence described so far in this program, 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

3 multiple choice options

If a population of protons moves through some distance during the time the echo is being sampled, what will be the appearance of the resulting image, provided that the gradients are operating properly for a simple spin-echo pulse sequence?

artifacts will appear in the phase encoding direction of the image

3 multiple choice options

If a proton moved along the direction of an increasing gradient, its rate of precession would:

increase

3 multiple choice options

During a six minute conventional scan, when is the data collected that is used to form the lower third of the image?

throughout the entire scan

3 multiple choice options

A give MR system claims its maximum gradient amplitude is 30 mT/meter. Imagine an ideal case in which the field strength at all points inside the magnet is 1.500 T. If a pulse sequence drives the x-gradient to its maximum amplitude the field strength at a point which is centered along the x-direction and displaced one meter toward the positive z-direction is __________ Tesla.

1.500

3 multiple choice options

Which physical gradient must be used for slice selection in order to produce a sagittal image?

x

3 multiple choice options

If a population of protons moves through some distance during the time the 90° RF pulse is applied, what will be the appearance of the resulting image, provided that the gradients are operating properly for a simple spin-echo pulse sequence?

artifacts will appear in the phase encoding direction of the image

3 multiple choice options

In order to disturb the protons in a particular location of the body, what must the frequency of the RF energy be?

matched to the precessional frequency of the patient's protons at that location

3 multiple choice options

A given MR system claims its maximum gradient amplitude is 30 mT/meter. Imagine an ideal case in which the field strength at all points inside the magnet is 1.500 T. If a pulse sequence drives the z-gradient to its maximum amplitude, the field strength at the center of the magnet is __________ Tesla.

1.500

3 multiple choice options

Which of the following is contained within a single spin-echo?

many frequencies

3 multiple choice options

On a coronal image, if frequency encoding is accomplished with the z-gradient, which physical gradient is used for phase encoding?

x

3 multiple choice options

Decreasing the slice select gradient amplitude will have what affect on the resulting slice if the RF transmitter bandwidth is held constant?

increase the slice thickness

3 multiple choice options

In an ideal 0.2 T magnet with perfect homogeneity, if the y-gradient amplitude is y mT/m and a proton's magnetization has a precessional frequency of 8.62 MHz, the proton's approximate displacement along the y-direction is __________cm. (Assume the gyromagnetic ratio equals 42.56).

36

3 multiple choice options

Which gradient will make the precessional frequency of the magnetization of protons in the patient's left eye different than that in the patient's right heel?

x, y or the z

3 multiple choice options

Along what direction are motion artifacts always seen?

along the phase direction of the image

3 multiple choice options

Along what direction are chemical shift artifacts always seen?

along the frequency direction of the image

3 multiple choice options

The frequency encoding gradient must be turned on during which of the following events?

readout of the echo

3 multiple choice options

In a 1.0 T MR system, which of the following statements is FALSE regarding the RF energy if no gradient is applied while a 42.56 MHz 90° RF pulse is being transmitted?

1. it will be absorbed by all protons in the range of the transmitting antenna

2. it will be absorbed by only the protons at the center of the magnet

3. it will cause all protons in the range of the transmitting antenna to generate transverse magnetization

2 only

3 multiple choice options

Which of the following is a linearly varying magnetic field?

a gradient

3 multiple choice options

Which physical gradient must be used for slice selection in order to produce a coronal image?

y

3 multiple choice options

Which physical gradient could be used for phase encoding in a sagittal image?

y or z

3 multiple choice options

Which of the following is TRUE regarding the Fourier Transform?

it separates the phase and frequency components corresponding to each point of anatomy in the image plane

3 multiple choice options

Which of the following has an effect on the resulting slice thickness?

the range of frequencies at which the RF energy is applied

3 multiple choice options

Which of the following statements is FALSE?

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

3 multiple choice options

In an ideal 1.5 T magnet with perfect homogeneity, if a proton experiences a magnetic field of 1.504T and the x-gradient amplitude is 16mTm, the displacement of the proton along the x-direction is __________cm.

25

3 multiple choice options

The slice select gradient must be turned on during which of the following events?

application of RF energy

3 multiple choice options

Which of the following is NOT determined by the slice select process

field of view

3 multiple choice options

Which of the following is NOT an essential part of localizing the MR signal generated during an MR study?

moving the patient within the magnet to ensure only the center slice is imaged

3 multiple choice options

in a vertical field magnet, which axis corresponds to the longitudinal direction, if the patient is in a head-first supine position?

y

3 multiple choice options

What effect will an applied gradient have on a population of stationary, in-phase protons within a 10 cm sphere at the center of the magnet?

it will increase the phase dispersion

3 multiple choice options

A positive change in frequency followed by an equal negative change in frequency, both for the same duration, will __________ the net phase of stationary protons.

have no effect on

3 multiple choice options

In an ideal 1.0 T magnet with perfect homogeneity, if a proton experiences a magnetic field of 1.006 T and is positioned 0.5 meter along the positive z-direction and centered along the x and y-directions, the z-gradient amplitude is __________mT/m.

12

3 multiple choice options

Given a sagittal image, which of the following statements is ALWAYS TRUE?

slice selection was accomplished with the x gradient

3 multiple choice options

Using a traditional pulse sequence, which of the following is FALSE regarding a single echo?

it contains the anatomical information from a specific line of the resulting image

3 multiple choice options

To make an oblique image which is oriented at an angle between transverse and coronal, which of the following physical gradients must be applied for slice selection?

y and z together

3 multiple choice options

If the z-gradient is applied, which of the following statements is TRUE regarding a patient's protons?

those in the patient's left ear precess at a different frequency than those in the patient's right knee

3 multiple choice options

Which of the following gradients is NOT balanced for phase?

phase encoding

3 multiple choice options

The magnetization of proton A makes one revolution of its precessional motion every 0.030 microseconds. The magnetization of proton B makes one revolution of its precessional motion every 0.015 microseconds. Therefore, the frequency of the magnetization of proton A is __________ the frequency of the magnetization of proton B.

one half

3 multiple choice options

The phase encoding gradient must be turned on during which of the following events?

prior to echo collection, but the exact timing isn't critical

3 multiple choice options