13 Mri2

Question 1

3 itwms

form the basis for evaluating the MR image characteristics

Answer 1

Spatial resolution, contrast sensitivity, and SNR parameters

Question 2

is the major attribute of MR

Answer 2

Contrast sensitivity

Question 3

1 is an indication of RF coil sensitivity to induced currents in
response to signals emanating from the patient. Coil losses that lead to lower SNR are
caused by patient “loading” effects and eddy currents, among other factor.

2 refers to the electric impedance characteristics of the body, which to a certain extent
acts like an antenna.

Answer 3

1 coil quality factor

2 Patient loading

Question 4

1 are signals that are opposite of the induced current produced by transverse
magnetization in the RF coil, and reduce the overall signal

Answer 4

Eddy

currents

Question 5

1 occurs from the nonrectangular RF excitation profiles in the spatial
domain and the resultant overlap of adjacent slices in multislice image acquisition
sequences.

Answer 5

Cross-excitation

Question 6

Often used for the two-dimensional image acquisition is a xxxx that produces relatively poor
anatomic contrast, yet provides a high-contrast “bright blood” signal

Answer 6

“GRASS” or “FISP” GE technique

Question 7

Cxx is a process that causes increased signal intensity due to
flowing protons; it occurs during imaging of a volume of tissues.

2 is a phenomenon that causes flow to exhibit increased signal on even echoes in
a multiple-echo image acquisition.

Answer 7

1 Flow-related enhancement

2 Even-echo rephasing

Question 8

The ____ relies on the tagging of blood in one region of the body
and detecting it in another. This differentiates moving blood from the surround stationary tissues

Answer 8

time-of-flight technique

Question 9

More clinically relevant are intravascular
blood pool agents such as 1 , which
modify the relaxation of protons in the blood in addition to producing a shorter T2*.

Answer 9

gadolinium–diethylenetriaminepentaacetic acid

Question 10

Ccc is the result of selective observation of the interaction
between protons in free water molecules and protons contained in the macromolecules
of a protein.
Magnetization exchange occurs between the two proton groups because
of coupling or chemical exchange.

Answer 10

Magnetization transfer contrast

Question 11

Rrr refers to the resonance frequency variations resulting from intrinsic magnetic shielding of anatomic structures

Answer 11

Chemical shift

Question 12

Errors in xxx affect all areas of the reconstructed image, and cause
the artifactual superimposition of wave patterns across the FOV.

Answer 12

k-space encoding

Question 13

Chemical shift artifacts of the second kind occur with 1 resulting from 2 of the echo in the same direction relative to the main magnetic field.

Signal appearance is dependent on the selection of TE. This happens because of constructive (in phase) or destructive (out of phase) transverse magnetization events that occur
periodically due to the difference in precessional frequencies.

Answer 13

1 GE images

2 the rephasing and dephasing

Question 14

The 1 will lead to a conventional chemical shift image of the first kind, while the 2 will lead to a chemical shift image of the second kind, manifesting a 3

Answer 14

1 in-phase timing
2 out-ofphase timing
3 dark rim
around heterogeneous water and fat anatomical structures

Question 15

1 occurs near sharp boundaries
and high-contrast transitions in the image, and appears as multiple, regularly spaced parallel bands of alternating bright and dark signal that slowly fades with distance

Answer 15

1 Ringing artifact (also known as Gibbs phenomenon)

Question 16

The 1 is a result of the mismapping of anatomy that lies outside of the FOV but within the slice volume.

The anatomy is usually 2.

It is caused by nonlinear gradients or by undersampling of the frequencies contained within the returned signal envelope.

Answer 16

1 wraparound artifact
2 displaced to
the opposite side of the image.

Question 17

coils are active or passive magnetic field devices that are used to adjust the mainmagnetic field and to improve the homogeneity in the sensitive central volume of the scanner

Answer 17

Shim coils

Question 18

_________ coils, as previously discussed, are wire conductors that produce a
linear superimposed gradient magnetic field on the main magnetic field. The gradient
coils are located inside the cylinder of the magnet, and are responsible for the banging
noise one hears during imaging. This noise is caused by the flexing and torque experienced by the gradient coil from the rapidly changing magnetic fields when energized.

Answer 18

Gradient