Imaging Weighting and Contrast Flashcards
What are the intrinsic parameters that cannot be changed?
- T1 recovery time
- T2 decay time
- Proton Density
What are the extrinsic parameters that can be changed?
- TR
- TE
- Flip Angle
What occurs at 1/2 the echo time?
180 degree refocusing
How is T1 weighting achieved?
short TR
short TE
How is T2 weighting achieved?
long TR
long TE
How is PD weighting achieved?
long TR
short TE
Short TR 350-800 ms
Short TE 0-25 ms
90-degree flip angle
180-degree refocus pulse
T1 weighted spin echo
Long TR >2500ms
Long TE 80-120 ms
90-degree flip angle
180-degree refocus pulse
T2 weighted spin echo
Long TR >2500ms
Short TE 0-25 ms
90-degree flip angle
180-degree refocus pulse
Proton Density weighted spin echo
Where is all the echoes stored in?
k-space
Short TR <800 ms
Min TE 0-5 ms
Flip Angle 70-90 degree
GRE T1 weighting
Short TR <800 ms
TE 20-40 ms
Flip Angle 5-25 degree
GRE T2* weighting
Which sequence is susceptible to local magnetic field inhomogeneity?
gradient echo (GRE) T2*
Fat or Water shows up bright in T1?
Fat
Fat or Water shows up dark in T2?
Fat
What doesn’t affect the contrast?
thickness of tissue
Fat or Water has higher proton density?
Fat
What is the most important factor in GRE sequence
flip angle
What is the process that flips protons through the transverse plane, catches up and creates an echo?
180 degree refocusing
Which weighting can never be in GRE echo pulse sequence?
true T2
Dark or Bright in T1 weighted: long T1 recovery?
dark
Dark or Bright in T2 weighted: short decay in transverse plane?
dark
What does more current create?
it creates steeper gradient field
