Chapter 3
echo at time t∈∙ The measurement is repeated after time spacing fR.
|
(-------- |
________________⅛_____________________________I |
-----------------) Repeat.. _____Time | |||
|
ξ_________ 90o |
I code |
180 o |
g read |
Echo | |
|
A A A | |||||
|
0 ' |
------------------------------------------------∣-J----∣-W-------------------------r | ||||
Figure 3.6 Sequence of MRI 1-D profile measurement
Magnetic gradient pulse is applied during echo signal collection. The total
signal at the time of the echo is [2]:
¾(0 = jp(z)exp[-i/Gz(t-tE)]dz [3.31]
A Fourier transform of Sz(t) yields the spin density p(z).
Signal amplitude at position z is proportional to spin density ρ(z) and can be
expressed as the function of T∣, T2, fR and ⅛ pl:
A = AQ(l-e~tRlTl)e~tE,T2 [3.32]
3.4.2. Ti weighted 1-D MRI profile measurement
When the oil∕water concentration is varying as a function of z, the contrast in
the spin density is not large enough to give useful information of oil/ water
distribution. This is the case for water-in-diluted bitumen emulsions in which large
drops may accumulate at the bottom while small drops may stay at the top. To
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