Chapter 12 MR Image Contrast Weighting

Question 1

A MR images contrast weighting is determined by several factors:

Answer 1

intrinsic and extrinsic

Question 2

what are intrinsic parameters that affect contrast weighting?

Answer 2

-T1 relaxation time
-T2 relaxation time
-Proton (Spin) Density
-Diffusion
-Perfusion & Flow

Question 3

what are extrinsic parameters that affect contrast weighting?

Answer 3

-the particular pulse sequence
-contrast parameters such as TR, TE, TI and flip angle

Question 4

water has ____ T1, T2, T2* relaxation times

Answer 4

LONG

Question 5

fat has ____ T1, T2, T2* relaxation times

Answer 5

short

Question 6

Most pathology will result in an increase in ______in the area of disease or injury

Answer 6

water

Question 7

The TR (time of repetition) is the time

Answer 7

between the initial excitation pulses in sequence.

Question 8

Based on the T1 relaxation time of a tissue the TR will

Answer 8

determine how much longitudinal magnetization recovers between repetitions of the sequence

Question 9

TR controls the:

Answer 9

amount of T1 weighting in an image

Question 10

the lower the TR, the _____T1 weighting

Answer 10

MORE

Question 11

the higher the TR, the ____T1 weighting

Answer 11

LOWER

Question 12

since fat has a short T1 relaxation time, tissues containing a significant amount of fat are _______on T1 weighted images

Answer 12

brighter

Question 13

tissues containing a significant amount of fluid are _______on T1 weighted images

Answer 13

darker

Question 14

CSF is pure water so it has the longest T1 relaxation time between it and white matter & gray matter

Answer 14

so it is dark on T1 images

Question 15

white matter contains nerve fibers which are wrapped in myelin, a protective coating that is mostly fat.

Answer 15

it has the shortest T1 relaxation time because it contains the most fat and will be brighter

Question 16

gray matter contains nerve cell bodies which are surrounded in extra cellular fluid so it

Answer 16

has a longer T1 relaxation time than white matter but still shorter than CSF

Question 17

TE (Time to Echo)

Answer 17

the time period between excitation and the center of the echo

Question 18

TE determines

Answer 18

how much transverse magnetization has decayed at the time of sampling based on the T2 relaxation time of the tissue

Question 19

TE controls the amount of

Answer 19

T2 weighting in the image

Question 20

the_____the TE, the _____the T2 weighting

Answer 20

shorter;less

Question 21

For a gradient echo sequence, TE controls

Answer 21

the amount of T2* weighting in the image

Question 22

If a T1 weighted image is desired, a ____ TR will be selected

Answer 22

Short. The TE will also be short. The short TE does not make it T1 weighted it makes it less T2 weighted.

Question 23

If a T2 weighted image is desired, a ____ TR will be selected

Answer 23

LONG; the long TR does not make it T2 weighted, it makes it less T1 weighted.
For T2 weighting, a long TE will be selected

Question 24

For a PD weighted image, a ___TR is selected to the contrast less T1 weighted and a ____TE is selected to make it less T2 weighted.

Answer 24

LONG TR;SHORT TE

Question 25

For T1 weighting:
A short TR would likely be between ______.
a short TE would be short if it were ______.

Answer 25

400-700msec; 25 msec or less

Question 26

For T2 weighting:
a long TR would likely be______
a long TE would be ________.

Answer 26

3000msec or higher
80-120msec

Question 27

For Proton Density:
a long TR would likely be______
a short TE would be short if it were ______.

Answer 27

3000 msec or higher
25 msec or less