Browsing by Author "Paul, JS"

Now showing 1 - 2 of 2
  • Item
    MR image enhancement using an extended neighborhood filter
    (JOURNAL OF VISUAL COMMUNICATION AND IMAGE REPRESENTATION, 2014) Paul, JS; Mathew, JJ; Kesavadas, C
    A filtering scheme is proposed for contrast enhancement within a Region-Of-Interest (ROI) containing unconnected foreground regions of narrow spatial extent such as multiple sclerosis, or ischemic lesions in Magnetic Resonance (MR) images. This involves determination of localized multiplicative weights in the spatial domain using an extended set of neighborhood directions. The degree of enhancement is shown to depend on the number of such directions, as determined from the size of a rectangular lattice, together with a threshold value used for computing the multiplicative weights. Best performance in respect of visual quality is achieved by choosing a threshold corresponding to the maximum Contrast Ratio, and lattice size corresponding to the maximum Peak Signal-to-Noise Ratio within the ROI. It is shown that the proposed filter overrides Localized Histogram based Equalization (LHE) based techniques in terms of computational complexity, preservation of structural similarity and attaining the maximum extent of contrast stretching. (C) 2014 Elsevier Inc. All rights reserved.
  • Item
    Partial Fourier Reconstruction Using Subspace Projection
    (2013 FOURTH NATIONAL CONFERENCE ON COMPUTER VISION, PATTERN RECOGNITION, IMAGE PROCESSING AND GRAPHICS (NCVPRIPG), 2013) Uma, K; Chandrasekharan, K; Paul, JS
    Scan time reduction in MRI can be achieved by partial k-space reconstruction. Truncation of the k-space results in generation of artifacts in the reconstructed image. A subspace projection algorithm is developed for artifact-free reconstruction of sparse MRI. The algorithm is applied to a frequency weighted k-space, which fits into a signal-space model for sparse MR images. The application is illustrated using Magnetic Resonance Angiogram (MRA).