EXAM #5 — MODULE 5

Question 1

[Image Weighting ]

T1 weighted image:

Image contrast is determined primarily by __ relaxation differences between different tissues (not due to __ relaxation differences between tissues).

Answer 1

[Image Weighting]

T1 weighted image:

Image contrast is determined primarily by T1 relaxation differences between different tissues (not due to T2 relaxation differences between tissues).

Question 2

[Image Weighting]

T2 weighted image:

Image contrast is determined primarily by __ relaxation differences between different tissues (not due to __ relaxation differences between tissues).

Answer 2

[Image Weighting]

T2 weighted image:

Image contrast is determined primarily by T2 relaxation differences between different tissues (not due to T1 relaxation differences between tissues).

Question 3

[Image Weighting]

…is accomplished by manipulating the pulse sequence factors:

__ and __

Excitation flip _____ also influences image weighting (TBD later)

Answer 3

[Image Weighting]

…is accomplished by manipulating the pulse sequence factors:

TR and TE

Excitation flip angle also influences image weighting (TBD later)

Question 4

[Image Weighting]

Degree of longitudinal (Z magn) relaxation that occurs is determined by __ length

Answer 4

[Image Weighting]

Degree of longitudinal (Z magn) relaxation that occurs is determined by TR length

Question 5

[Image Weighting]

Degree of transverse (XY magn) relaxation that occurs is determined by __ length

Answer 5

[Image Weighting]

Degree of transverse (XY magn) relaxation that occurs is determined by TE length

Question 6

[Image Weighting]

If TR selected is short, there is _____ difference in T1 relaxation (Mz regeneration) between different tissues

Answer 6

[Image Weighting]

If TR selected is short, there is much difference in T1 relaxation (Mz regeneration) between different tissues

Question 7

[Image Weighting]

If TR selected is long, there is _____ difference in T1 relaxation (Mz regeneration) between different tissues (all tissues have time to fully regrow their Mz)

Answer 7

[Image Weighting]

If TR selected is long, there is not much difference in T1 relaxation (Mz regeneration) between different tissues (all tissues have time to fully regrow their Mz)

Question 8

[Image Weighting]

If TE selected is short (TE1), there is _____ difference in T2 relaxation (Mxy degeneration) between different tissues (all tissues haven’t had time to degenerate much, so their Mxy’s are _____)

Answer 8

[Image Weighting]

If TE selected is short (TE1), there is not much difference in T2 relaxation (Mxy degeneration) between different tissues (all tissues haven’t had time to degenerate much, so their Mxy’s are similar)

Question 9

[Image Weighting]

If TE selected is long (TE2), there is _____ difference in T2 relaxation (Mxy degeneration) between different tissues

Answer 9

[Image Weighting]

If TE selected is long (TE2), there is much difference in T2 relaxation (Mxy degeneration) between different tissues

Question 10

[Image Weighting Parameters ]

T1 weighted:
_____ TR , _____ TE

T2 weighted:
_____ TR , _____ TE

Proton Density:
_____ TR , _____ TE

Signal too weak:
_____ TR , _____ TE

Answer 10

[Image Weighting Parameters]

T1 weighted:
short TR , short TE

T2 weighted:
long TR , long TE

Proton Density:
long TR , short TE

Signal too weak:
short TR , long TE

Question 11

MRI image contrast…

…is created by different __ and __ relaxation rates between _____

Answer 11

MRI image contrast…

…is created by different T1 and T2 relaxation rates between tissues

Question 12

[MRI Weighting ]

Proton density weight-ing demonstrates fine _____ and _____ matter _____

Answer 12

[MRI Weighting]

Proton density weight-ing demonstrates fine gray and white matter contrast

Question 13

[Proton Density weighted (a) vs T1 weighted (b) ]

(c) Repeat proton-density-weighted MRI scan and (d) TI-weighted MRI scan demonstrate dramatic progressive, confluent abnormal signal intensity within the deep _____ _____ nuclei and relative lack of involvement of the hemispheric _____ _____.

Administration of gadolinium demonstrates extensive enhancement within the deep _____ _____ nuclei.

Answer 13

[Proton Density weighted (a) vs T1 weighted (b)]

(c) Repeat proton-density-weighted MRI scan and (d) TI-weighted MRI scan demonstrate dramatic progressive, confluent abnormal signal intensity within the deep gray matter nuclei and relative lack of involvement of the hemispheric white matter.

Administration of gadolinium demonstrates extensive enhancement within the deep gray matter nuclei.

Question 14

[Proton Density weighted (a) vs T1 weighted (b)]

a) Proton-density-weighted MRI scan demonstrates abnormal increased signal intensity within the _____ nuclei, _____ nuclei and _____ thalami.
(b) TI-weighted MRI scan after the administration of gadolinium demonstrates areas of contrast enhancement within the _____ ganglia and intense enhancement within the _____ region.

Answer 14

[Proton Density weighted (a) vs T1 weighted (b)]

a) Proton-density-weighted MRI scan demonstrates abnormal increased signal intensity within the caudate nuclei, lentiform nuclei and medial thalami.
(b) TI-weighted MRI scan after the administration of gadolinium demonstrates areas of contrast enhancement within the basal ganglia and intense enhancement within the habenular region.

Question 15

8. T1 weighted image: Difference in signal intensity between tissues (the tissue contrast) is due mainly to differences in T1 between the tissues; obtained with _____ TR and _____ TE (figs 32, 42)
   a. By using a _____ TR, signal intensity differences among varying tissues due to T1 relaxation differences are maximized (large difference in longitudinal magnetization among tissues) (fig 32)
9. _____ TR yields higher tissue contrast in image due to T1 relaxation differences among tissues
   b. _____ TE: signal differences due to differing T2s (transversal degradation) among varying tissues have not yet become pronounced
10. Contrast not caused by __ differences among tissues
    c. MR image produced with many _____
11. T1 differences among various tissues are sampled each time net magnetization flips into _____ plane by successive _____
    d. T1 relaxation time influences appearance on a __ weighted image
12. White brain matter - _____ T1: brightest on image
13. Gray brain matter - _____ T1: next brightest on image
14. CSF - _____ T1: darkest on image (fig 1-10 mic)

Answer 15

8. T1 weighted image: Difference in signal intensity between tissues (the tissue contrast) is due mainly to differences in T1 between the tissues; obtained with short TR and short TE (figs 32, 42)
   a. By using a short TR, signal intensity differences among varying tissues due to T1 relaxation differences are maximized (large difference in longitudinal magnetization among tissues) (fig 32)
9. Short TR yields higher tissue contrast in image due to T1 relaxation differences among tissues
   b. Short TE: signal differences due to differing T2s (transversal degradation) among varying tissues have not yet become pronounced
10. Contrast not caused by T2 differences among tissues
    c. MR image produced with many RF pulse excitations
11. T1 differences among various tissues are sampled each time net magnetization flips into transverse plane by successive RF pulses
    d. T1 relaxation time influences appearance on a T1 weighted image
12. White brain matter - very short T1: brightest on image
13. Gray brain matter - longer T1: next brightest on image
14. CSF - even longer T1: darkest on image (fig 1-10 mic)

Question 16

__ weighted image: fat appears bright, fluids dark in image

Answer 16

T1 weighted image: fat appears bright, fluids dark in image

Question 17

9. T2 weighted image: Differences in signal intensity between tissues (tissue contrast) due to differences in T2 relaxation (transverse magnetization degeneration) between tissues (figs 37, 41): obtained with _____ TR and _____ TE

a. _____ TE: transverse magnetization degeneration among various tissues
varies moreso over time, creating larger differences in signal intensity and thus higher MR image contrast with long TE (fig 37; pg 56)

1. _____ TE: signal intensity difference between tissues depends on T2 (transversal relaxation time) differences among tissues; thus contrast between tissues at long TE is influenced by T2 relaxation differences between the tissues (longer TE: greater T2 difference).

(Note: very _____ TE-signal gets weaker & always present noise stays same→causes smaller signal-to-noise ratio - grainy image)

b. _____ TR: signal intensity differences are not due to differing T1s (longitudinal regeneration), since longitudinal magnetization has totally regenerated (and is essentially the same) for all tissues (fig 32; pg 49)

Answer 17

9. T2 weighted image: Differences in signal intensity between tissues (tissue contrast) due to differences in T2 relaxation (transverse magnetization degeneration) between tissues (figs 37, 41): obtained with long TR and long TE

a. Long TE: transverse magnetization degeneration among various tissues
varies moreso over time, creating larger differences in signal intensity and thus higher MR image contrast with long TE (fig 37; pg 56)

1. Longer TE: signal intensity difference between tissues depends on T2 (transversal relaxation time) differences among tissues; thus contrast between tissues at long TE is influenced by T2 relaxation differences between the tissues (longer TE: greater T2 difference).

(Note: very long TE-signal gets weaker & always present noise stays same→causes smaller signal-to-noise ratio - grainy image)

b. Long TR: signal intensity differences are not due to differing T1s (longitudinal regeneration), since longitudinal magnetization has totally regenerated (and is essentially the same) for all tissues (fig 32; pg 49)

Question 18

**T2 weighted image: fluids (CSF, urine) appear _____, fat _____ in image

c. 90° pulse: _____ magnetization tilted to _____ magnetization
d. RF pulse switched off, _____ magnetization degenerates
1. Protons lose _____
2. Results in loss of _____
e. 180° RF pulse introduced at _____: acts as a rubber wall
1. Transverse magnetization vectors reverse precessing direction and _____ at the point of TE (at start line) (fig 35, pg 53)
2. Causes reappearance of _____ (a _____ signal)
3. Subsequent 180° pulses _____ protons and _____ signal
a. signals become progressively _____ intense due to T2 effects: at each TE protons are less absolutely rephased
1. Protons don’t rephase completely at TE due to inconstant local _____ magnetic field _____ in tissue (due to T2 effects)
a. Race cars: start race, 180° RF pulse - reverse direction, rephase at start line; with repeated 180° pulses, fewer cars reach start line due to internal accidents (in which energy is transferred from proton to proton: called spin-spin interactions)
f. Immediately after TE: protons begin to lose _____ _____ again

Answer 18

**T2 weighted image: fluids (CSF, urine) appear bright, fat dark in image

c. 90° pulse: longitudinal magnetization tilted to transverse magnetization
d. RF pulse switched off, transversal magnetization degenerates
1. Protons lose phase coherence
2. Results in loss of signal intensity
e. 180° RF pulse introduced at TE/2: acts as a rubber wall
1. Transverse magnetization vectors reverse precessing direction and rephase at the point of TE (at start line) (fig 35, pg 53)
2. Causes reappearance of signal intensity (a spin echo signal)
3. Subsequent 180° pulses rephase protons and regenerate signal
a. signals become progressively less intense due to T2 effects: at each TE protons are less absolutely rephased
1. Protons don’t rephase completely at TE due to inconstant local internal magnetic field inhomogeneities in tissue (due to T2 effects)
a. Race cars: start race, 180° RF pulse - reverse direction, rephase at start line; with repeated 180° pulses, fewer cars reach start line due to internal accidents (in which energy is transferred from proton to proton: called spin-spin interactions)
f. Immediately after TE: protons begin to lose phase coherence again

Question 19

**T2 weighted image: fluids (CSF, urine) appear _____, fat _____ in image

1. at end of TR interval #1: RF pulse #__ is transmitted - tilts regrown _____ vector into _____ vector
2. RF pulse turned off: _____ vector degenerates, _____ vector regenerates + grows
3. At end of TR interval #2: RF pulse #__ is transmitted - tilts regrown _____ vector into _____ vector
   * length of _____ determines length of regrown _____ vector and thus amount of _____ vector we start out with
4. TE interval: time we wait after _____ to sample signal; determines how much _____ vector length (signal intensity) is sampled
   * at end of TE interval; signal is _____; many _____ signals are used to construct an image (the cycle is repeated many times to create an image) (fig 38, pg 59; fig 39, pg 60)
   * TE interval starts immediately at new __

Answer 19

**T2 weighted image: fluids (CSF, urine) appear bright, fat dark in image

1. at end of TR interval #1: RF pulse #2 is transmitted - tilts regrown longitudinal vector into transversal vector
2. RF pulse turned off: transversal vector degenerates, longitudinal vector regenerates + grows
3. At end of TR interval #2: RF pulse #3 is transmitted - tilts regrown longitudinal vector into transversal vector
   * length of TR interval determines length of regrown longitudinal vector and thus amount of transversal vector we start out with
4. TE interval: time we wait after 90° RF pulse to sample signal; determines how much transversal vector length (signal intensity) is sampled
   * at end of TE interval; signal is sampled; many sampled signals are used to construct an image (the cycle is repeated many times to create an image) (fig 38, pg 59; fig 39, pg 60)
   * TE interval starts immediately at new TR

Question 20

10. Proton Density weighted (Spin Density weighted) image: Where there are no protons, there is _____ signal; where there are many protons, there will be _____ signals
    a. Tissue contrast influenced by the _____ of protons within tissues
    b. _____ TR and _____ TE yields proton density (spin density) weighted image (fig 40)
11. With long TR, resulting image contrast is due mainly to differences in proton _____ among varying tissues (not due to differences in T1 relaxation among varying tissues, since all tissues have regained longitudinal magnetization after a long TR)
    * By using a long TR, signal intensity differences among varying tissues due to T1 relaxation differences are _____ (small difference in longitudinal magnetization among tissues)
    a. Long TR: image contrast not attributable to __ relaxation differences among tissues

Answer 20

10. Proton Density weighted (Spin Density weighted) image: Where there are no protons, there is no signal; where there are many protons, there will be many signals
    a. Tissue contrast influenced by the concentration of protons within tissues
    b. Long TR and short TE yields proton density (spin density) weighted image (fig 40)
11. With long TR, resulting image contrast is due mainly to differences in proton densities among varying tissues (not due to differences in T1 relaxation among varying tissues, since all tissues have regained longitudinal magnetization after a long TR)
    * By using a long TR, signal intensity differences among varying tissues due to T1 relaxation differences are minimized (small difference in longitudinal magnetization among tissues)
    a. Long TR: image contrast not attributable to T1 relaxation differences among tissues

Question 21

10. Proton Density weighted (Spin Density weighted) image: Where there are no protons, there is _____ signal; where there are many protons, there will be _____ signals
11. With short TE, resulting image contrast is due mainly to differences in proton _____ among varying tissues (not due to differences in T2 relaxation among varying tissues, since differences in transverse magnetization degeneration have not had a chance to become pronounced
    * By using a short TE, signal intensity differences among varying tissues due to T2 relaxation differences are _____ (differences in transverse magnetization among tissues are not yet significant)
    a. Short TE: image contrast not attributable to __ relaxation differences among tissues

Answer 21

10. Proton Density weighted (Spin Density weighted) image: Where there are no protons, there is no signal; where there are many protons, there will be many signals
11. With short TE, resulting image contrast is due mainly to differences in proton densities among varying tissues (not due to differences in T2 relaxation among varying tissues, since differences in transverse magnetization degeneration have not had a chance to become pronounced
    * By using a short TE, signal intensity differences among varying tissues due to T2 relaxation differences are minimized (differences in transverse magnetization among tissues are not yet significant)
    a. Short TE: image contrast not attributable to T2 relaxation differences among tissues

Question 22

Proton Density Weighted image: brain grey matter contains more water (protons) than white matter; grey matter signal intensity is _____ than that of white matter; grey matter (outer) appears _____ than that of white matter (inner)

Answer 22

Proton Density Weighted image: brain grey matter contains more water (protons) than white matter; grey matter signal intensity is higher than that of white matter; grey matter (outer) appears brighter than that of white matter (inner)

Question 23

Scenario: 2 tissues, A and B (fig 46, pg 68)

• A has shorter T1 and T2 relaxation than B
• T2 relaxation curves of tissues A & B intersect
• technologist selects TE:
• if chosen TE is before A & B T2 curve intersection (ie: we choose TE short):

1. Tissue A w/ shorter T1 regrows _____ longitudinal magnetization, 90° RF pulse converts it to _____ transversal vector
2. Tissue B w/ longer T1 regrows _____ longitudinal magnetization, 90° RF pulse converts it to _____ transversal vector
3. tissue A will have _____ signal intensity than B
4. Signal intensities from tissues A & B are determined by differences in their __ relaxations: image is __ weighted

Answer 23

Scenario: 2 tissues, A and B (fig 46, pg 68)

• A has shorter T1 and T2 relaxation than B
• T2 relaxation curves of tissues A & B intersect
• technologist selects TE:
• if chosen TE is before A & B T2 curve intersection (ie: we choose TE short):

1. Tissue A w/ shorter T1 regrows more longitudinal magnetization, 90° RF pulse converts it to longer transversal vector
2. Tissue B w/ longer T1 regrows less longitudinal magnetization, 90° RF pulse converts it to shorter transversal vector
3. tissue A will have higher signal intensity than B
4. Signal intensities from tissues A & B are determined by differences in their T1 relaxations: image is T1 weighted

Question 24

Scenario: 2 tissues, A and B (fig 46, pg 68)

• if chosen TE is at A & B T2 curve intersection:
  1. tissues A & B will have same signal intensity - no contrast

2. this is why 2 exams w/ different T1 and T2 weighting are performed
   - if chosen TE is beyond A & B T2 curve intersection (ie: we choose TE long):
3. tissue A will have _____ signal intensity than B
4. Differences in in signal intensities from tissues A & B are not determined by T1 magnetization differences, but by differences in their __ magnetizations: image is __ weighted

Answer 24

Scenario: 2 tissues, A and B (fig 46, pg 68)

• if chosen TE is at A & B T2 curve intersection:
  1. tissues A & B will have same signal intensity - no contrast

2. this is why 2 exams w/ different T1 and T2 weighting are performed
   - if chosen TE is beyond A & B T2 curve intersection (ie: we choose TE long):
3. tissue A will have lower signal intensity than B
4. Differences in in signal intensities from tissues A & B are not determined by T1 magnetization differences, but by differences in their T2 magnetizations: image is T2 weighted

Question 25

11. Short TR and very long TE
    a. Very short TR: very _____ longitudinal magnetization to be tilted into transverse plane
    b. very long TE: transverse magnetization mostly _____
    c. signal intensity very _____; cannot be used to create a useable image

Answer 25

11. Short TR and very long TE
    a. Very short TR: very little longitudinal magnetization to be tilted into transverse plane
    b. very long TE: transverse magnetization mostly disappears
    c. signal intensity very small; cannot be used to create a useable image