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Fig. 3. Radon transform analysis. (A) Pixel grayscale values are summed along rows
(in the direction of the green arrows), creating a column of row-intensity
values. This is done iteratively as the image is rotated through 179°. (B)
The resulting set of row-intensity columns is arrayed by rotation angle
(orientation), and these columns are summed to create a density distribution
(C). The peak of the density distribution therefore corresponds to the primary
orientation of objects within the image. (D-G) This method reliably detects
the orientation of radially arrayed struts (D), regardless of induced noise
(E) or the removal of the image center (F), but will not produce a false
signal for pure noise (G).