  We present an edge preserving and denoising filter for enhancing the features
in images, which contain an ROI having a narrow spatial extent. Typical
examples include angiograms, or ROI spatially distributed in multiple locations
and contained within an outlying region, such as in multiple-sclerosis. The
filtering involves determination of multiplicative weights in the spatial
domain using an extended set of neighborhood directions. Equivalently, the
filtering operation may be interpreted as a combination of directional filters
in the frequency domain, with selective weighting for spatial frequencies
contained within each direction. The advantages of the proposed filter in
comparison to specialized non-linear filters, which operate on diffusion
principle, are illustrated using numerical phantom data. The performance
evaluation is carried out on simulated images from BrainWeb database for
multiple-sclerosis, acute ischemic stroke using clinically acquired FLAIR
images and MR angiograms.
