25 Spot Finding and Measurement

Expression array images contain thousands of spots, and the intensity of each of these needs to be measured. Before this can occur, it is necessary to find the spots. This chapter presents a method for finding the center of spots in a slide.

25.1 Spot Finding

Although microarray slides are printed by a computerized robot, the user defines the number of spots and the geometry of the spots on the slide. For example, the slides used here as examples contain 16 × 24 blocks, and each block contains 5 × 5 spots. Often individual spots are referenced by their block location as well as their location within the block.

Figure 25-1 shows just a small portion with six blocks each containing 5 × 5 spots. These spots are mostly ...

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