Image Processing Reference
In-Depth Information
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(a)
(b)
(c)
FIGURE 11.19
The effect of zero filling. Zero filling was performed from 16 to 32 data
points in both dimensions in k-space (k-space of the first time point shown). (a) Area in the
rectangle represents the original k-space, while zeros were added symmetrically, resulting
in the increase of the number of voxels from the original value (b) 16 × 16 to (c) 32 × 32.
Equation 11.24 implies that a multiplication of all k-space values S (t, k
l,
) by
a proper phase factor before the DFT
−1
results in shifting all positions of the
voxels (the whole spectroscopic grid). This is very useful because partial volume
effects play an important role due to the large voxel size, and by means of grid
shifting, the area of interest can be centered in the voxel (
Figure 11.20
).
11.3.6
D
ISPLAY
OF
THE
CSI D
ATA
Spectroscopic imaging data usually contain substantial amounts of information.
To make use of this information efficiently, proper display and analysis of the
data are required.
There are several ways of presenting spectroscopic imaging data sets. Similar
to SVS, one or few selected spectra can be viewed as shown in
Figure 11.21a
.
This provides spectra in high resolution and enables their reliable inspection. To
view all spectra simultaneously, a grid of spectra overlaying the MR scout image
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