Hi Mike,
in principle you have (at least) two possibilities for calibrating
gradient strenght.
1. You performe a gradient echo sequence with increasing graddients.
Due to the STEJSKAL-TANNER equ. you can determine the diffusion coeff.
If you take a sample with well kown D, you can determine the gradient
instaed.
You should take "water", D is well kown an tabulated.
2. You 'll take a phantom sample and make a "picture" of it, i.e. gradient
"ON" during acquisition.
For that, you'll need a special pulse sequence.
Then you can correlate the frequency lenght of the picture to the lenght
of the phantom.
We took a Teflon slice of 2 mm. You may fix this by a thin glas capillary
on the tube's buttom.
The tube itselves is filled with D2O (99%At, to observe the rest protons).
To avoid bubbles a little whole is in the center of the teflon slice.
The disandvantage is, that this phantom is not easy to prepare. Teflon is
a "soft" material wich "unshapes" under pressure, so the thickness could
vary.
See Berger's book . ("200 and more..")
Greetings
Matthias Findeisen
Univ. Leipzig
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