Capstone - midterm CNI

If slice thickness increases?

Spatial Resolution Decrease

Which of the following statements is FALSE ?

-T2 relaxation occurs much more quickly than T1 relaxation

-T1 relaxation and T2 relaxation occurs simultaneously

-T1 relaxation refers to the longitudinal recovery of magnetization while T2 relaxation refers to the transverse decay of magnetization

-echoes collected in the tranverse plane demonstrates only T2 relaxation differences

echoes collected in the tranverse plane demonstrates only T2 relaxation differences

What is the definition of T1 relaxation?

The time it takes the net longitudinal magnetization of protons to grow 63% of its final amplitude

Based on the graph of longitudinal relaxation, which of the following has the shortest T1 relaxation time?

Bone Marrow

Which of the following techniques has no effect upon the scan time?

respiratory compensation

The strong MR signal that comes sometime after 180 RF pulse?

Echo

The proton's ____ contributes to its magnetic properties?

1 & 3 (spinning motion and mass)

On a T2-weighted image, CSF appears bright because it has a ____ relaxation time?

Long T2

The RF pulse should be transmitted at a frequency of approximately ____ MHz in order to disturb protons experiencing a 4-tesla field?

170-degree

What is NOT a requirement for magnetic resonance imaging?

ionizing radiation

What is the time from the initial RF excitation pulse to the next RF excitation pulse for a given slice called?

TR

What's the definition of T2 relaxation time?

The time it takes the net transverse magnetization to decay to 63% of its initial amplitude

By decreasing the TE from 100 ms to 40 ms on a spin-echo pulse sequence, what is the expected result?

T2 contrast minimized

If six successive 180 RF pulses are applied, following a 90 RF pulse, echo____ will contain the weakest signal?

Six

Using a spin-echo pulse sequence which generates two echoes, imaging a hypothetical tissue in which the protons never experience spin-spin interactions. How does the signal from the first echo compare to the signal from the second echo?

it is the same size

Which of the following dephasing mechanisms is NOT rephrased by 180* RF pulse?

spin - spin interaction

The effect of an I.V. administered paramagnetic contrast agent used in MRI is a shortening of the T1 relaxation time of the protons within any perfused tissue. A vascular lesion would appear_____ on a T1-weighted contrast-enhanced image as compared to its appearance on a T1-weighted unenhanced image?**

brighter

If the field strength experienced by a patient within an MR magnet is increased, the precessional frequency of the magnetization of the patient's protons will?

Increase

The image shown is an example of what type of contrast?

T1 Weighted

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 every 0.015 microsecond. Therefore, the frequency of the magnetization of proton A is ____ the frequency of the magnetization of proton B?

one half

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

entire scan

TR=3000, TE=100, TI=150, ETL=12. What pulse sequence are you most likely doing?**

T2 Flair

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 which are exposed to

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

x or y

Which of the following is a linearly varying magnetic field?

Gradient

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

application of RF energy

What influences the resulting slice thickness?

the range of frequencies encoded in the echo

Given a Coronal image, what statement is always true?

-the frequency encoding direction extends from the bottom to the top of the image

-slice selection was accomplished with the x gradient

-slice selection was accomplished with the Z gradient

-frequency encoding was accomplished with the x gradient

slice selection was accomplished with the Z gradient

Which of the following statements is FALSE?

-gradients linearly vary the magnetic field

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

-gradients, applied in an equal but opposite fashion, can ensure the phase will not accumulate

-gradients cause the precessional frequency of protons to vary with position

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

If the z-gradient is applied, what statement is true regarding a patient's protons?

Those in the patients left ear precess at a different frequency thaThose in the patients' right knee

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

the readout gradient

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

it will increase the phase dispersion

If a population of protons moves through some distance during the term 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

A given MR system claims its maximum gradient amplitude is 10 mT/meter. Imaging in an ideal case in which the field strength at all the points inside the magnet is 1.500T. 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.

1.490

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

X, Y, or the Z

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 32m/m, the displacement of the proton along the x-direction is___cm

12.5

NO QUESTION

NO QUESTION

The purpose of the shims is to

make the main magnetic field more uniform

The correct location of the z-gradient coils in a superconductive MRI system is wrapped___a cylinder within the bore of the magnet ?

completely around each end of

Which of the following MRI system components is responsible for the timing and correct performance of each component once the sequence has been started ?

pulse sequence controller

Gradient rise time is defined as which of the following ?

the time required for a gradient to reach its specified amplitude beginning from a resting state

The ADC MRI systems is responsible for ?

digitizing the MR signal into a form recognizable by a computer

The Fourier Transform is performed by which MRI system component ?

array processor

Which of the following components is NOT located within the bore of the magnet ?

passive magnetic shielding

The echoes emitted from the patient's body are passed through the pre-amplifier to ?

greatly increase the strength of their tiny signals

______magnets can NOT lose their magnetic field without being disassembled ?

Permanent

________shielding is another name for Faraday shielding ?

radio frequency

When a different RF coil is used for transmitting than the RF coil used for receiving, they must be decoupled. What is decoupling ?

electrically isolating the two coils, so that the RF energy is only applied to the transmitter coil

______magnets require a constant connection to a power source in order to maintain their magnetic field ?

Resistive

Which of the following types of magnets can have their magnetic fields reduced to zero in the shortest amount of time ?

Resistive

________ magnets are used on most MRI systems produces today ?

1. Permanent

2. Superconducting

3. Resistive

1,2 & 3

The fringe field of a 1.5T superconductive magnet extends along which of the following directions?

A- x and y direction only.

all

If two saturation regions are applied during a dual contrast fast spin echo study of the lumbar spine, how many 90* pulses are applied during a single repetition, for a given slice?

3

Which of the following statements is TRUE?

superconducting magnets can produce magnetic fields of 10 T

Some manufacturers have incorporated a Faraday shield into the design of their magnets, thus eliminating the need to enclose the entire magnets, thus eliminating the need to enclose the entire magnet room with RF shielding. Which of the following is TRUE regarding this self-shielded type of MR system ?

installation costs will be decreased since expensive metal in the magnet room walls can be avoided

Consider the dual contrast spin echo pulse sequence shown in Fig 4-45 in which the 90 RF pulse is applied as the time = 0, the center of the first echo forms at the time = 15ms, and the center of the second echo forms at time = 90ms. the 180 RF pulse to form the echo used for the T2-weighted image must have been applied at____ms

52.5

When the gradient moment nulling is added to a pulse sequence and all other parameters are unchanged, the ?

scan time may be decreased

A region of interest about 5 cm below the surface of the skin. If you only have four circular coils to choose from, a ____ cm diameter coil will have the best sensitivity to signal from the region of interest and at the same time provide the highest signal-to-noise ratio?

10

Upon installing a new MRI system, the service engineer mistakenly connects the x-gradient amplifier to the y-gradient coil, the y-gradient amplifier to the z-gradient coil, and the z-gradient amplifier to the x-gradient coil. What type of image would result when the technologist runs the first sagittal scan?

a coronal image

In an image which does NOT employ flow compensation, which of the following explains the reason for a dark signal in a vessel with normal flow?

1-the signal from the protons in blood always appears dark on T1 and T2-weighted images.

2-the signal from the protons in blood is mipmapped along the phase encoding direction of the image.

3-there are no hydrogen protons in flowing blood.

2 only

Which of the following may be T1 weighted ?

all

In the diagram of a fast spin echo pulse sequence in Fig below, the center of echo # 1 occurs at ______ ms

IMAGE

35

The ______in order to reduce the chemical shift artifact on the image in figure ?

Receiver bandwidth should be increased.

Of the following sequences is best for performing diffusion-weighted imaging ?

echo planar image

In the fast spin echo pulse sequence with an echo train of 8, if the first four echoes contribute to a proton density image, and the last four echoes contribute to a T2-weighted image, how many repetitions are required to fill the raw data of a 256x256 T2-weighted image ?

64

Which of the following is NOT related to the receiver bandwidth?

the range of frequencies transmitted to select the slice thickness

In order to partially compensate for changes in S/N, how should the TR be adjusted when moving from a 1.5 tesla system to a 0.3 tesla system?

1-the TR should be decreased

2-the TR should be increased

3-the TR has no effect on the S/N

2 Only

Which of the following may NOT be seen in a conventional spin echo image ?

the phase effects of magnetic susceptibility

Which of the following may be seen in a steady state fast gradient echo image ?

2 and 3

Assuming all other parameters are the same, a____ ms echo time provides the strongest T1 contrast?

1

A set of images is acquired with a 150 mm FOV, keeping all other parameters constant, a second set of images is acquired with a 300 mm FOV, and then magnified so that the anatomical structures in the first and second set of images appear the same size. Which of the following statements is FALSE?

1-the spatial resolution of the second set of images is better than the first set of images

2-the S/N of the second set of images is worse than the first set of images

3-The scan time of the second set of images is twice that of the first set of images

1 & 3

Which of the following is NOT rephrased by the 180* RF pulse in a spin echo pulse sequence?

phase effects of chemical shift

Which of the following RF flip angles would result in the largest longitudinal component, assuming the net magnetization is initially in the longitudinal direction?

45

Assuming all other parameters are the same, a _____ms echo time provides the strongest T2 contrast ?

110

Which of the following pulse sequence parameters is responsible for partial volume averaging?

Slice thickness

Which of the following echo train lengths generates a set of images in the shortest amount of time, assuming all other parameters are the same?

5

Because______, the inversion recovery method of fat suppression should NOT be used with MR contrast agents ?

The enhanced tissues as well as the fat may be suppressed

When using a rectangular FOV, which is twice as tall as it is wide, and the phase direction of the image is oriented along the smaller dimension of the FOV, which of the following relationships between the frequency and phase steps of the matrix guarantees square pixels?

the number of phase steps must be half of the number of frequency steps

In a fast spin echo pulse sequence, the time from the 90* pulse to the echo is called ?

TE

Which of the following is NOT included in T2 contrast ?

spin-lattice relaxation

The smallest object that can be resolved in an image acquired with a 24 cm FOV and a 512 x 512 matrix is____mm?

0.47

During a spoiled gradient echo pulse sequence with 12 slices, how many gradient echoes are collected during one TR period?

12

In the 2-prepared fast gradient echo sequence which uses a 90, 180, 90 preparation scheme, how many 90 RF pulses are applied for a single image with 192 phase steps in its matrix ?

384

In which of the following pulse sequences would you expect to find the shortest TR ?

gradient echo

Which of the following statements is true?

1-1 contrast is maximized with short TRs

2- Contrast is the difference in magnetizations of two tissues.

3- T2 contrast is maximized with short TEs

1 & 2

A technique used to reduce the MR scan time which requires the use of an array coil ?

Parallel imaging

Which of the following types of sequences was most likely used to generate the image in the figure ?

FSE

Which of the following is NOT related to the receiver bandwidth?

the range of frequencies transmitted to select the slice thickness

If the pulse sequence allows a maximum of 18 slices for the desired repetition time, and 9 cm of anatomy must be covered, the minimum slice thickness we could use to cover the region of interest, if we were to leave no gap is ____mm ?

5

When converting the recommended protocol for a fat suppression inversion recovery sequence from a low field MR system to a high field system, the_____in order to maintain equivalent fat nulling ?

T1 should be increased

Assuming all other parameters are the same, an echo time of ____ ms provides the best S/R?

15

Which of the following statements is FALSE regarding a gradient echo sequence?

RF flip angles which are less than 90* allow for greater signal-to-noise ratios when using short TRRF flip angles which are less than 90* allow for greater signal-to-noise ratios when using short TRs

Which of the following is a method of reducing the effects of crosstalk ?

1-reducing the gap between slices

2-alternating the slice order

3-contiguous imaging

2 only

Assuming the coordinate system shown in figure, if gradient moment nulling is applied only along the slice direction of a transverse set of brain image, which physical gradient must use extra pulses?

z gradient

In what orientation and position should a saturation region be in order to eliminate carotid blood flow from transverse images of the cervical spine ?

Transverse, superior to the region of interest

If the radiologist requires 2 mm slice through the pituitary and 2.4cm of coverage, how many slices must be selected (assuming no gap) ?

12

If we also want to rephrase the signal from protons that have a more complex motion, extra____ must be added to the standard gradient moment nulling gradient waveform which rephrases the signal from protons with a constant velocity ?

Spoiler

As the number of signal averages is increased from 1 to 3, which of the following does NOT occur?

the signal-to-noise ratio is three times better

The echoes collected from a 256x256 sagittal lumbar spine image have a frequency range that extends 14.1 kHz above and 14.1 kHz below the central frequency of the echoes. If this exam was performed on a 1.5 tesla MRI system, where there is approximately 220Hz chemical shift between the fat and water, the signal in the vertebral bodies will shift ____ pixels relative to the signal in the desk ?

2

Which of the following techniques would be inefficient at reducing motion artifacts created by blood flowing through the sagittal sinus?

fat saturation