Image Processing Reference
In-Depth Information
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chemical shift (ppm)
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chemical shift (ppm)
FIGURE 11.9
Results of water suppression with (a) a single pulse and (b) with a com-
bination of three pulses for different amplitudes of the water saturation pulse.
frequency selective imaging (8) and later applied to volume-selective spectros-
copy, e.g., by Sijens et. al (9). Usually, a pulse with a Gaussian shape is used for
water suppression. The success of water suppression is very sensitive to the flip
angle of the saturating pulse. Because the exact value of this flip angle varies
within the examination volume of a subject, the correct amplitude of the water
suppression pulse is often adjusted prior to each volume-selective measurement.
In a series of measurements with varying transmitter values, the one with an
optimal water saturation is selected (Figure 11.9a). Improved water suppression
can be obtained if a combination of pulses is used instead of only one pulse. The
result of a transmitter adjustment for a three-pulse combination is shown in
Figure 11.9b. In this case, the relation between transmitter values was 89:83:161
with a time delay of 60 msec between the pulses. This pulse combination was
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