Background: Fundus image is a projection of the inner surface of the eye,
which can be used to analyze and judge the distribution of blood vessels on
the retina due to its different shape, bifurcation and elongation. Vascular
trees are the most stable features in medical images and can be used for
biometrics. Ophthalmologists can effectively screen and determine the
ophthalmic conditions of diabetic retinopathy, glaucoma and microaneurysms
by the morphology of blood vessels presented in the fundus images.
Traditional unsupervised learning methods include matched filtering method,
morphological processing method, deformation model method, etc. However, due
to the great difference in the feature complexity of different fundus image
morphology, the traditional methods are relatively simple in coding, poor in
the extraction degree of vascular features, poor in segmentation effect, and
unable to meet the needs of practical clinical assistance. Methods: In this
paper, we propose a new feature fusion model based on non-subsampled
shearwave transform for retinal blood vessel segmentation. The contrast
between blood vessels and background is enhanced by pre-processing. The
vascular contour features and detailed features are extracted under the
multi-scale framework, and then the image is postprocessed. The fundus
images are decomposed into low frequency sub-band and high frequency
sub-band by non-subsampled shear-wave transform. The two feature images are
fused by regional definition weighting and guided filtering respectively,
and the vascular detection image is obtained by calculating the maximum
value of the corresponding pixels at each scale. Finally, the Otsu method is
used for segmentation. Results: The experimental results on DRIVE data set
show that the proposed method can accurately segment the vascular contour
while retaining a large number of small vascular branches with high
accuracy. Conclusion: The proposed method has a high accuracy and can
perform vascular segmentation well on the premise of ensuring sensitivity.