udej8 onvenience. Assume the following values for T1 and T2: for white matter (WM): T1 = 500 nsec for cerebrospinal fluid (CSF): T1 = 2000, T2 = 200 msec Also assume a spin density N oth WM and CSF. a. For a TR = 2000 msec, find the relative signal intensities for WM and CSF (i.e., point A and B on the graph). b. Calculate the crossover TE where WM and CSF have identical T2 weighting (point C c. Now, calculate the signal intensities of WM and CSF for TE = 25 (first echo) and TE = 100 msec (second echo), and the ratio CSF/WM.

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Chapter5: Analysis Of Convection Heat Transfer
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1- In the graph in the Following Figure, the T1 and T2 curves are plotted simultaneously for
convenience. Assume the following values for T1 and T2: for white matter (WM): T1 500, T2 = 100
msec for cerebrospinal fluid (CSF): T1 = 2000, T2 = 200 msec Also assume a spin density N = 100 for
both WM and CSF.
a. For a TR = 2000 msec, find the relative signal intensities for WM and CSF (i.e., points
A and B on the graph).
b. Calculate the crossover TE where WM and CSF have identical T2 weighting (point C).
c. Now, calculate the signal intensities of WM and CSF for TE = 25 (first echo) and TE =
100 msec (second echo), and the ratio CSF/WM.
d. Repeat (a) to (c) for TR = 3000 msec and observe how one gets more T2 weighting in
the 2nd echo (higher ratio CSF/WM).
e. Now, calculate the signal intensities for TR = 3000 and TE = 200 msec. Notice that
despite relative loss of signal for both WM and CSF, the ratio CSF/WM actually increases,
indicating more T2 weighting (i.e., CSF gets brighter on the images).
100%-
Signal
Intensity
WM
CSF
TR
TE
TR
TE (crossover)
T1 and T2 curves are plotted simultaneously. Use this graph to answer the questions
2- Match the following: (i) reduces T1 effect; (ii) enhances T1 effect; (iii) reduces T2
effect; (iv)enhances T2 effect with:
a- short TR--
b- long TR--
c- short TE
d- long TE-
3- For a material having a T2 of 80 msec 320 msec after a 90 pulse, what is the relative
magnitude of the MR signal compared to the maximum signal.
4- If a material has a longitudinal relaxation time constant T1 = 200 msec, what will the
MR signal S be 200 ms after an RF pulse has flipped (nutated) the bulk magnetization
into the transverse plane?
Transcribed Image Text:1- In the graph in the Following Figure, the T1 and T2 curves are plotted simultaneously for convenience. Assume the following values for T1 and T2: for white matter (WM): T1 500, T2 = 100 msec for cerebrospinal fluid (CSF): T1 = 2000, T2 = 200 msec Also assume a spin density N = 100 for both WM and CSF. a. For a TR = 2000 msec, find the relative signal intensities for WM and CSF (i.e., points A and B on the graph). b. Calculate the crossover TE where WM and CSF have identical T2 weighting (point C). c. Now, calculate the signal intensities of WM and CSF for TE = 25 (first echo) and TE = 100 msec (second echo), and the ratio CSF/WM. d. Repeat (a) to (c) for TR = 3000 msec and observe how one gets more T2 weighting in the 2nd echo (higher ratio CSF/WM). e. Now, calculate the signal intensities for TR = 3000 and TE = 200 msec. Notice that despite relative loss of signal for both WM and CSF, the ratio CSF/WM actually increases, indicating more T2 weighting (i.e., CSF gets brighter on the images). 100%- Signal Intensity WM CSF TR TE TR TE (crossover) T1 and T2 curves are plotted simultaneously. Use this graph to answer the questions 2- Match the following: (i) reduces T1 effect; (ii) enhances T1 effect; (iii) reduces T2 effect; (iv)enhances T2 effect with: a- short TR-- b- long TR-- c- short TE d- long TE- 3- For a material having a T2 of 80 msec 320 msec after a 90 pulse, what is the relative magnitude of the MR signal compared to the maximum signal. 4- If a material has a longitudinal relaxation time constant T1 = 200 msec, what will the MR signal S be 200 ms after an RF pulse has flipped (nutated) the bulk magnetization into the transverse plane?
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