Table 2. B-COSFIRE filter parameters for blood vessel segmentation. Parameters for both filters used in automatic segmentation are given in the table. Length denotes the length of a line segment to be detected, whereas orientations denotes the number of orientations used to achieve rotational invariance. Parameters depend on image resolution and sample characteristics, such as expected vessel dimensions and lengths. All units are in pixels.

parameter	symmetric filter	asymmetric filter
$\sigma$	$5.5$	$4.0$
$\rho$	$2$	$2$
length	$20$	$20$
orientations	$12$	$24$
${\sigma }_0$	$3$	$4$
$\alpha$	$0.7$	$0.1$