PHYSICAL PRINCIPLES Signal Generation
nuclei, protons and spins longitudinal relaxation T1 transverse relaxation T2 exitation and relaxation relation between T1...
transverse relaxation T2 Spin - Spin relaxation signal generation
X Y Z B o signal generation transverse relaxation T2
X Z B o Y signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o signal generation transverse relaxation T2
X Y Z B o Signal signal generation transverse relaxation T2
X Y Z B o Signal signal generation transverse relaxation T2
X Y Z B o Signal signal generation transverse relaxation T2
X Y Z B o Signal signal generation transverse relaxation T2
X Y Z B o Signal dephasing signal generation transverse relaxation T2
S time F ree  I nduction  D ecay signal FID T2 signal generation transverse relaxation T2
T2 S T2 definition T2: the time that passes untill 63% of the original signal has been lost time 63 % signal generation tr...
T2 S T2* time signal generation transverse relaxation T2* Due to magnetic inhomegeneities the transverse relaxation is los...
X Y Z B o signal generation transverse relaxation T2
X Y Z B o transmit coil radio frequency transmitter signal generation transverse relaxation T2
X Y Z B o transmit coil radio frequency transmitter 180 º 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
X Y Z B o 180 º signal generation transverse relaxation T2
180 º refocusing pulse signal generation transverse relaxation T2
refocusing pulse 180 º 180 º signal generation transverse relaxation T2
T2 envelope signal generation transverse relaxation T2
in conclusion: <ul><li>T 1  relates to magnetisation </li></ul><ul><li>T 2  relates to signal </li></ul>signal generation
nuclei, protons and spins longitudinal relaxation T1 transverse relaxation T2 excitation and relaxation relation between T...
Upcoming SlideShare
Loading in …5
×

04 relajacion transversal

1,095 views

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,095
On SlideShare
0
From Embeds
0
Number of Embeds
16
Actions
Shares
0
Downloads
47
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide
  • THIS IS THE
  • Transverse relaxation is also called Spin-Spin relaxation. The speed of rotation is influenced by the neighbouring protons. Compare with walking in a shopping mall on a Saturday afternoon. While walking you have to change your speed and direction constantly to avoid collisions whith other shoppers. The only difference is that protons do collide.
  • When we look at one single proton, we can see that it makes one 360 degree rotation in a certain time...
  • ...
  • ... But in the same time the red proton has covered more than 360 degrees, and the blue proton less.
  • After the next rotation these differences are bigger.
  • ..and bigger
  • ...
  • Back to the first rotation and look at the signals that belong to the protons..
  • ...
  • ...
  • ...
  • ...
  • Now we add the summed signal, and you can see that the signal is getting weaker the more the protons are pointing in different directions.
  • ...
  • ...
  • ...
  • The signal shift relative to each other, cancelling each other out. This is called dephasing.
  • The signal that is generated after the 90 degree pulse is called FID or T2*.
  • And is different for the various tissues. The time untill 63% of the signal has ´´died´´ is called the T2 time.
  • And is different for the various tissues. The time untill 63% of the signal has ´´died´´ is called the T2 time.
  • At the dawn of MR this signal could not be measured, because the hardware did not allow the fast switching. So we had to find a trick to overcome this problem.
  • For that we need the help of the transmit coil again.
  • When we transmit a signal for so long time that the protons are flipped over 180 degrees, look what happens..
  • ...
  • ...
  • ...
  • ...
  • ...
  • The slow protons will be overtaken by the faster ones, thus generating a new strong signal.
  • ...
  • ...
  • ...
  • In other words. The signal is restored with the help of a 180 degree pulse, resulting in a strong echo.
  • Thats why we call it a refocussing pulse.
  • As you saw, after the rephasing of the protons they will dephase again. And again we can apply a 180 degree pulse in order to rephase them, resuting in new signal or echo...
  • The curve that we can draw through the tops of the echos is called the T2-envelope.
  • .
  • .
  • 04 relajacion transversal

    1. 1. PHYSICAL PRINCIPLES Signal Generation
    2. 2. nuclei, protons and spins longitudinal relaxation T1 transverse relaxation T2 exitation and relaxation relation between T1 and T2 signal generation
    3. 3. transverse relaxation T2 Spin - Spin relaxation signal generation
    4. 4. X Y Z B o signal generation transverse relaxation T2
    5. 5. X Z B o Y signal generation transverse relaxation T2
    6. 6. X Y Z B o signal generation transverse relaxation T2
    7. 7. X Y Z B o signal generation transverse relaxation T2
    8. 8. X Y Z B o signal generation transverse relaxation T2
    9. 9. X Y Z B o signal generation transverse relaxation T2
    10. 10. X Y Z B o signal generation transverse relaxation T2
    11. 11. X Y Z B o signal generation transverse relaxation T2
    12. 12. X Y Z B o signal generation transverse relaxation T2
    13. 13. X Y Z B o signal generation transverse relaxation T2
    14. 14. X Y Z B o signal generation transverse relaxation T2
    15. 15. X Y Z B o Signal signal generation transverse relaxation T2
    16. 16. X Y Z B o Signal signal generation transverse relaxation T2
    17. 17. X Y Z B o Signal signal generation transverse relaxation T2
    18. 18. X Y Z B o Signal signal generation transverse relaxation T2
    19. 19. X Y Z B o Signal dephasing signal generation transverse relaxation T2
    20. 20. S time F ree I nduction D ecay signal FID T2 signal generation transverse relaxation T2
    21. 21. T2 S T2 definition T2: the time that passes untill 63% of the original signal has been lost time 63 % signal generation transverse relaxation T2
    22. 22. T2 S T2* time signal generation transverse relaxation T2* Due to magnetic inhomegeneities the transverse relaxation is lost faster !! T2 T2*
    23. 23. X Y Z B o signal generation transverse relaxation T2
    24. 24. X Y Z B o transmit coil radio frequency transmitter signal generation transverse relaxation T2
    25. 25. X Y Z B o transmit coil radio frequency transmitter 180 º 180 º signal generation transverse relaxation T2
    26. 26. X Y Z B o 180 º signal generation transverse relaxation T2
    27. 27. X Y Z B o 180 º signal generation transverse relaxation T2
    28. 28. X Y Z B o 180 º signal generation transverse relaxation T2
    29. 29. X Y Z B o 180 º signal generation transverse relaxation T2
    30. 30. X Y Z B o 180 º signal generation transverse relaxation T2
    31. 31. X Y Z B o 180 º signal generation transverse relaxation T2
    32. 32. X Y Z B o 180 º signal generation transverse relaxation T2
    33. 33. X Y Z B o 180 º signal generation transverse relaxation T2
    34. 34. X Y Z B o 180 º signal generation transverse relaxation T2
    35. 35. X Y Z B o 180 º signal generation transverse relaxation T2
    36. 36. 180 º refocusing pulse signal generation transverse relaxation T2
    37. 37. refocusing pulse 180 º 180 º signal generation transverse relaxation T2
    38. 38. T2 envelope signal generation transverse relaxation T2
    39. 39. in conclusion: <ul><li>T 1 relates to magnetisation </li></ul><ul><li>T 2 relates to signal </li></ul>signal generation
    40. 40. nuclei, protons and spins longitudinal relaxation T1 transverse relaxation T2 excitation and relaxation relation between T1 and T2 signal generation

    ×