. Author manuscript; available in PMC: 2009 Sep 14.

Published in final edited form as: Proc Int Conf Image Proc. 2008 Oct 12;2008:1804–1807. doi: 10.1109/ICIP.2008.4712127

Table 1.

Possible orientation patterns based on the eigenvalues $λ_{1, 2} = \frac{1}{2} (L_{x x} + L_{y y} \pm \sqrt{{(L_{x x} - L_{y y})}^{2} + {(2 L_{x y})}^{2}})$ (|λ₁| ≤ |λ₂|, H = high, L = low) [18].

λ₁	λ₂	orientation pattern

L	L	Flat or Noise no preferred direction
H−	L	Bright tubular structure
H+	L	Dark tubular structure
H−	H−	Bright blob-like structure
H+	H+	Dark blob-like structure