Fig. 2.

Computer-aided estimate of the surface area fractal dimension (D) of a vascular network in two-dimensional biopsy sections. (A) Pituitary tissue section stained with antibodies raised against CD34 that specifically react with vessels. (B) Image segmentation: the immunopositive vessels are selected on the basis of the similarity of the colour of adjacent pixels. (C) Determination of D using the box-counting algorithm which, briefly, counts the number of boxes of length ɛ required to cover the object being measured, and indicated as N(ɛ). (D) Prototypical curve obtainable using the box-counting method that highlights the so-called fractal windows ranged by box size ɛ₁ and ɛ₂, and represents the appropriate region in which to estimate the dimension. Box sizes of more than ɛ₂ approach the size of the image until one box covers it completely. Box sizes smaller than ɛ₁ approach a single pixel or the resolution of the image.