Fluke Biomedical 76-903 - Manual (Page 11)

Theory of Operation
Flood Section
3
3-3
Figure 3-4. Diameter, 9", Depth, 1.25"
3.3.1 RF Uniformity
The flood section is used to measure RF uniformity and to visualize artifacts that can come from many
different sources (Figure 3-5).
Figure 3-5.
Radio-frequency (brightness) non-uniformity can come from various sources. Most RF coils have a
number of active wires and the regions near the wires can show increased signal intensity. It can also
come from magnetic field uniformity, eddy current problems and poor RF power setting. RF uniformity can
also be affected by internal motion of the solution. One should also look for any aliasing, fold-over or
ghosts.
3.3.2 T
1
and T
2
Values
A single value of T
1
and T
2
can be measured using the flood section. It should be pointed out that T
1
and
T
2
values depend on magnetic field strength, temperature, imaging sequence, and they are very difficult to
measure precisely. Extreme caution should be taken for RF power setting.
An insert with 6 vials is available SO that various solutions can be imaged for a range of relaxation values.
3.4 Insert Section
This section has the following inserts:
1. Folded Step Ramps: Slice thickness and slice contiguity (gap), phantom orientation.
2. Resolution Pattern: Square hole pattern for positive contrast.