Figure 2.

Illustration of GA BER measurement based on the Euclidean distance map (EDM). The large square represents the imaging field, and the small squares represent individual pixels. (A) A GA lesion affecting four pixels (blue squares) at year 0. (B) After we performed an EDM transformation to the mask of the GA lesion at year 0, the value in each pixel of the EDM now indicated the shortest distance from this pixel to the GA lesion. The values in pixels affected by GA (blue pixels) are 0. (C) The enlarged GA lesion (orange squares) after 1 year of follow-up. (D) After we overlay the border of GA lesion at year 1 on the EDM shown in (B), we were able to obtain the shortest distances (i.e., values in the orange pixels) from the pixels on the GA border at year 1 to the GA border at year 0. These values represent GA BERs over 1 year of follow-up.