332
Q. Chen et al.
Fig. 11.35 GA projection image by combining two GA characteristics. Final GA projection image
(Left). One line profile (Right)
Figure 11.35 (Left) shows the final GA projection image obtained with the
Eq. (11.1), which combines the two GA characteristics: bright choroid and thin
RPE. Figure 11.35 (Right) shows one line profile of the 170th rows of Figs. 11.34
(Right) and 11.35 (Left), marked with the dashed line in Fig. 11.35 (Left). The
RPE thickness map can enhance the GA display by suppressing the background, as
marked with the dashed black circles in Fig. 11.35 (Right). The edge slope between
the GA (marked with the dashed gray circle in the middle) and background regions
indicates that the final projection image (Fig. 11.35 (Left)) has a better contrast for
the GA visualization than the RSVP projection image (Fig. 11.34 (Right)). Since the
background intensity near the GA boundary is suppressed by the RPE thickness map,
the intensity gradient of the GA boundary is higher in the final GA projection image
than that in the RSVP projection image. This is helpful for enabling automated GA
segmentation. While within the GA region, the intensity values have some decrease
in the final GA projection image.
11.3.4.6 False Color Fusion
The proposed drusen and GA projection techniques described above are specific to
display one pathological feature (either drusen or GA). To display drusen and GA
simultaneously in one image, we adopted a false color fusion strategy. The three
components (R, G, B) of the false color image consist of the SVP projection image,
the drusen image, and the GA projection image, respectively. Figure 11.36 shows
the false color fusion result (Bottom Right) by combining the SVP projection image
(Top Left), drusen (Top Right) and GA projection (Bottom Left) images. It could
be observed that GA appears in the R and B components, and drusen appears in the
G component. We also noticed that drusen are darker in the GA projection image
because they reduce the choroidal brightness. However, it is noticeable that in the
false color image, the drusen is greenish and the GA is purple hue. The false color
Q. Chen et al.
Fig. 11.35 GA projection image by combining two GA characteristics. Final GA projection image
(Left). One line profile (Right)
Figure 11.35 (Left) shows the final GA projection image obtained with the
Eq. (11.1), which combines the two GA characteristics: bright choroid and thin
RPE. Figure 11.35 (Right) shows one line profile of the 170th rows of Figs. 11.34
(Right) and 11.35 (Left), marked with the dashed line in Fig. 11.35 (Left). The
RPE thickness map can enhance the GA display by suppressing the background, as
marked with the dashed black circles in Fig. 11.35 (Right). The edge slope between
the GA (marked with the dashed gray circle in the middle) and background regions
indicates that the final projection image (Fig. 11.35 (Left)) has a better contrast for
the GA visualization than the RSVP projection image (Fig. 11.34 (Right)). Since the
background intensity near the GA boundary is suppressed by the RPE thickness map,
the intensity gradient of the GA boundary is higher in the final GA projection image
than that in the RSVP projection image. This is helpful for enabling automated GA
segmentation. While within the GA region, the intensity values have some decrease
in the final GA projection image.
11.3.4.6 False Color Fusion
The proposed drusen and GA projection techniques described above are specific to
display one pathological feature (either drusen or GA). To display drusen and GA
simultaneously in one image, we adopted a false color fusion strategy. The three
components (R, G, B) of the false color image consist of the SVP projection image,
the drusen image, and the GA projection image, respectively. Figure 11.36 shows
the false color fusion result (Bottom Right) by combining the SVP projection image
(Top Left), drusen (Top Right) and GA projection (Bottom Left) images. It could
be observed that GA appears in the R and B components, and drusen appears in the
G component. We also noticed that drusen are darker in the GA projection image
because they reduce the choroidal brightness. However, it is noticeable that in the
false color image, the drusen is greenish and the GA is purple hue. The false color