Image Reconstruction for 3D Lung Imaging - Department of Systems ...

also showed an increased Radial PE due to the contrast being pushed toward the tank
centre for phantoms located in the end sections. This effect was less noticeable with the
Planar EP configuration. Both the Planar and Planar-Offset EP configurations show little
degradation due to electrode plane separation errors of up 20% (6cm on the 28cm tall tank).
The Planar-Offset is slightly more robust than the Planar EP configuration in this regard.
6.3.5 2D Limitations
In addition to the seven 3D EP configurations additional reconstructions were performed
using the same 3D meshes but with the 16 electrodes arranged in a single plane at a height
of 14cm. The plots of figure 6.11 were generated similarly to those of section 6.2.3: 28
data frames from the r/2 phantom moving through 28 vertical locations. Figure 6.11(c)
validates the obvious insight that vertical position cannot be resolved using a single plane of
electrodes. Regardless of actual phantom height, the 2D arrangement always reconstructs
an image that is located in the plane of the electrodes. As the small target moves farther
away from the electrode plane the resolution, figure 6.11(a), and the image magnitude,
figure 6.11(d), both decrease while the the radial error, figure 6.11(b), increases.
Phantom Height (cm)
Phantom Height (cm)
25
20
15
10
5
25
20
15
10
5
Electrode Plane
0
0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.5 0.51 0.52
Resolution (BR)
Phantom Height
Image Height
(a) Resolution
5 10 15 20 25
Image Height (cm)
(c) Contrast
Electrode plane
Phantom Height (cm)
Phantom Height (cm)
25
20
15
10
5
25
20
15
10
5
Electrode Plane
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5
Radial Error (%)
(b) Radial Error
Electrode Plane
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Image Magnitude, Normalized to max=1
(d) Image Magnitude (Normalized)
Figure 6.11: Performance measures vs Phantom Height for noise free reconstructions with
single layer of 16 electrodes for the small target moving through 28 vertical positions at r/2.
6.3.6 Summary
A qualitative summary of the significant discriminators is presented in table 6.3. Five of
the configurations show poor performance in one or more of the discriminators while the
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