Comparative Study of Retinal Vessel Segmentation Based on Global Thresholding Techniques
Table 1
Phase congruence parameter description and optimum parameter values.
Parameter description
Parameter symbol
Parameter value (DRIVE)
Parameter value (STARE)
Number of wavelet scales.
4
3
Number of filter orientations.
norient
6
5
Wavelength of smallest scale filter.
minWaveLength
3
2.5
Scaling factor between successive filters.
mult
2.1
2.9
Ratio of the standard deviation of the Gaussian describing the log Gabor filter’s transfer function in the frequency domain to the filter center frequency.
sigmaOnf
0.55
1.5
Ratio of angular interval between filter orientations and the standard deviation of the angular Gaussian function used to construct filters in the frequency plane.
dThetaOnSigma
1.2
1.7
Number of standard deviations of the noise energy beyond the mean at which we set the noise threshold point.
2.3
3
The fractional measure of frequency spread below which phase congruency values get penalized.
cutOff
0.5
0.5
Controls the sharpness of the transition in the sigmoid function used to weight phase congruency for frequency spread.
