Mri Arrt Registry Review 2018

Front 1

TR INCREASED

Back 1

Benefits: INCREASED SNR & INCREASED # of Slices

Limitation: INCREASED Scan time & DECREASED T1 Weighting

Front 2

TR DECREASED

Back 2

Benefits: DECREASED SCAN TIME & INCREASED T1 Weighting

Limitations: DECREASED SNR & DECREASED # of Slices TE

Front 3

TE INCREASED

Back 3

Benefits: INCREASED T2 Weighting

Limitation: DECEADED SNR

Front 4

TE DECREASED

Back 4

Benefits: INCREASED SNR

LIMITATION: DECREASED T2 Weighting

Front 5

NEX INCREASED

Back 5

Benefits: INCREASED SNR & more signal averaging

Limitation: direct proportional increase in Scan time

Front 6

NEX DECREASED

Back 6

Benefits: Direct proportional decease in Scan time

Limitation: decreased SNR & less signal averaging

Front 7

Slice thickness increased

Back 7

Benefits: increased SNR & Increased coverage of anatomy

Limitation: Decreased spatial resolution & more partial voluming

Front 8

Slice thickness decreased

Back 8

Benefits: increased Spatial resolution & reduced partial volume averaging

Limitation: decreased SNR & decreased coverage of anatomy

Front 9

FOV Increased

Back 9

Benefit: Increased SNR & Increased coverage of anatomy

Limitation: Decreased spatial resolution & decreased likelihood of aliasing

Front 10

FOV Decreased

Back 10

Benefit: increased spatial resolution & increased likelihood of aliasing

Limitation: Decreased SNR & decreased coverage of anatomy

Front 11

Matrix increased

Back 11

Benefit: increased spatial resolution

Limitation: increased scan time and decreased SNR if pixel is small

Front 12

Matrix decreased

Back 12

Benefit: decreased scan time and increased SNR if pixel is large

Limitation: decreased spatial resolution

Front 13

Receive bandwidth increased

Back 13

Benefit: decrease in chemical shift and decrease in minimum TE

Limitation: decreased SNR

Front 14

Receive bandwith decreased

Back 14

Benefit: Increased SNR

Limitation: Increase in chemical shift and increase in minimum TE

Front 15

Launch coil

Back 15

Benefit: increased area of received signal

Limitation: lower SNR, sensitive to artifacts, aliasing with small FOV

Front 16

Small coil

Back 16

Benefit: Increased SNR, less sensitive to artifacts, less prone to aliasing with a small FOV

LIMITATION: Decreased area of received signal

Front 17

An RF pulse of what flip angle will maximize the component of the net magnetization projected into the transverse plane

Back 17

90 degree

Hint 17

The net magnetization is initially aligned with the main magnetic field before any RF energy is transmitted to the protons however, the magnetization can be measured in order to create MR images only when it is present in the transverse plane. Therefore, RF energy must be applied in order to deflect the net magnetization away from its alignment with the main magnetic field and projected into the transverse plane which is perpendicular to the axis of the main magnetic field ( RF flip angle )

Front 18

T1 Relaxation refers to ________ relaxation

Back 18

Longitudinal

Hint 18

T1time describes the ease with which protons dissipate the RF energy they absorbed during the transmission of an RF pulse . Immediately after an RF pulse is delivered to the protons, the longitudinal net magnetization is deflected into the transverse plane. The longitudinal net magnetization gradually recovers according to the T1 time of that population of protons. This process of recovery is called longitudinal relaxation.

Front 19

Which of the following statements is false?

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

B) T1 and T2 relaxation occurs simultaneously

C) echoes collected in the transverse plane demonstrate only T2 relaxation differences.

D) T2 relaxation occurs much more quickly than T1 relaxation

Back 19

C) Echoes collected in the transverse plane demonstrate only T2 relaxation differences

Hint 19

Depending upon specific imaging parameters used in a given MR measurement, echoes collected in the transverse plane can contain information concerning tissue contrast according to the tissues inherent proton densities, T1 relaxation times and T2 relaxation times. T2 relaxation describes the time course of spin spin interactions which calls decay of transverse magnetization. T1 relaxation describes the Tom course of spin lattice interactions which caused the recovery of longitudinal magnetization. T1 relaxation and T2 relaxation or independent processes but they occur simultaneously. However, in the vast majority of tissues, the T2 time is shorter than the T1time

Front 20

If the professional frequency of the protons net magnetization is approximately 21 MHz a ____ tesla magnetic field is being experienced by the patients protons

Back 20

0.5

Hint 20

In order to disturb protons, RF pulses are transmitted at the processional frequency of protons which is calculated by the Laramore equation: (proton processional frequency) =(magnetic field strength) x (proton gyromagnetic ratio). Assuming a gyromagnetic ratio of 42.6 MHz/Tesla for protons, the resulting field strength can be calculated.

Front 21

What is the definition of T1 relaxation?

Back 21

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

Hint 21

The T1 relaxation time describes the Tom course of the recovery of the longitudinal magnetization aligned with the main magnetic field. T one is defined as the amount of time required for the longitudinal magnetization to recover 63% of its full magnitude

Front 22

The edema associated with pathology in the brain has much longer T2 relaxation time than surrounding normal brain tissue. On a T2 weighted image what does this result in?

Back 22

A high signal intensity in the area of edema

Front 23

The edema associated with pathology in the brain has much longer T2 relaxation time than surrounding normal brain tissue. On a T2 weighted image what does this result in?

Back 23

A high signal intensity in the area of edema

Front 24

Which of the following dephasing mechanisms affects the size of the resulting spin echo?

Back 24

Spin – spin interactions

Front 25

After a 90° RF pulse, if three 180° RF pulses are applied to generate three echoes, which of the following is responsible for the third echo being smaller than the first echo?

Back 25

Spin – spin interactions

Front 26

The MR Echo is NOT:

A) detected as magnetic changes that induce a voltage into an RF coil

B) collected when the magnetization in the transverse plane has been rephased

C) A tiny signal containing contrast information necessary for tissue differentiation

D) collected only one time for a given image

Back 26

D) collected only one time for a given image

Hint 26

The tiny echo signal is generated by all of the protons within the excited slice and therefore contains contrast information about all of the tissues within that slice. It is detected when the transverse magnetization rephases and induces a voltage in a RF coil. The number of echoes collected is equal to the size of the acquisition matrix along the phase encoding direction

Front 27

What is the time from the initial RF excitation pulse to the echo called?

Back 27

TE / Echo Time

Hint 27

The T1 is the time between the initial 180° RF pulse and the 90° excitation pulse in an inversion recovery sequence. The TE is the time between the RF excitation pulse and the center of the echo. The TR is the time between successive RF excitation pulses

Front 28

The proton’s _________ contributes to its magnetic properties.

1) spinning motion

2) positive charge

3) mass

Back 28

1 & 2 Spinning motion and positive charge

Hint 28

A proton behaves like a charged, spinning particle which exhibits magnetic properties. It behaves like a tiny dipole, or bar magnet. An objects mass contributes to it inherent gravitational properties, but it has no effect on the objects magnetic properties. For example, a proton contains much more mass than an electron, although they both have opposite but equal charge. Likewise, a proton and neutron contain equal mass although the neutron contains no charge and demonstrates no magnetic properties

Front 29

True or False

More protons align with the main magnetic field then against the main magnetic field

Back 29

True

Front 30

On a T2 weighted image CSF appears bright because it has a _______________ relaxation time

Back 30

Long T2

Hint 30

CSF behaves like a water-based fluid because it has relatively long T1 and T2 times compared to other substances within the body. Because CSF has a long T1 time, a long TR must be used in a T2 weighted image in order to eliminate T1 weighted contrast effects. Because CSF has a long T2, spin spin interactions occur less frequently which allows more protons to contribute to the CSF signal compared to most other substances in the brain

Front 31

The processional frequency of the net magnetization of protons in a magnetic field is determined by which of the following?

Back 31

The Gyromagnetic ratio and the field strength

Front 32

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

Back 32

170

Front 33

Z axis

Back 33

Superior to Inferior

Top to bottom

Axial

Front 34

X axis

Back 34

Left to right

Sagittal

Front 35

Y axis

Back 35

Anterior to posterior

Coronal

Front 36

Which of the following is NOT a requirement for magnetic resonance imaging?

A) atomic nuclei with odd number of protons

B) A strong magnetic field

C) ionizing radiation

D) RF energy

Back 36

C) Ionizing radiation