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An objective method to identify optimum clip-limit and histogram specification of contrast limited adaptive histogram equalization for MR images

Joseph J., Sivaraman J., Periyasamy R., Simi V. R.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 3

489--497

EN

In contrast limited adaptive histogram equalization (CLAHE), the selection of tile size, clip-limit and the distribution which specify desired shape of the histogram of image tiles is paramount, as it critically influences the quality of the enhanced image. The optimal value of these parameters devolves on the generic of the image to be enhanced and usually they are selected empirically. In this paper, the degradation of intensity, textural and geometric features of the medical image with respect to the variation in clip-limit and specified histogram shape is analyzed. The statistical indices used to quantify the feature degradation are Absolute Mean Brightness Error (AMBE), Absolute Deviation in Entropy (ADE), Peak Signal to Noise Ratio (PSNR), Variance Ratio (VR), Structural Similarity Index Matrix (SSIM) and Saturation Evaluation Index (SEI). The images used for the analysis are axial plane MR images of magnetic resonance spectroscopy (MRS), under gradient recalled echo (GRE), diffusion weighted imaging (DWI) 1000b Array Spatial Sensitivity Encoding Technique (ASSET), T2 Fluid Attenuation Inversion Recovery (FLAIR) and T1 Fast Spin-Echo Contrast Enhanced (FS-ECE) series of pre-operative Glioblastoma-edema complex. The experimental analysis was performed using Matlab®. Results show that for MR images the exponential histogram specification with a clip-limit of 0.01 is found to be optimum. At optimum clip-limit, the mean of SSIM exhibited by the Rayleigh, uniform and exponential histogram specification were found to be 0.7477, 0.7946 and 0.8457, for ten sets of MR images and mean of variance ratio are 1.242, 2.0316 and 1.7711, respectively.

2

An analytical method for the adaptive computation of threshold of gradient modulus in 2D anisotropic diffusion filter

Joseph J., Periyasamy R.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

1--10

EN

In spite of the extensive application of Anisotropic Diffusion (AD) filter in software packages for medical image analysis, denoising and edge preservation offered by it depends exclusively on the selection of the value of Threshold of Gradient Modulus (TGM). Tuning the TGM to its optimum value through trial and error is subjective and tiring. An analytical model to compute the optimum value of TGM adaptively from the mean gradient of the image itself is proposed in this article. The qualitative examination of the gradient and true edge maps of the original and restored Magnetic Resonance images revealed that analytically computed TGM ensures best trade-off between noise suppression and edge preservation.

3

A full reference Morphological Edge Similarity Index to account processing induced edge artefacts in magnetic resonance images

Kuppusamy P. G., Joseph J., Sivaraman J.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

159--166

EN

An objective measure of edge similarity between the original and processed images to quantify the processing induced artefacts in medical image computing is proposed in this article. Globally accepted Image Quality Analysis (IQA) indices such as Peak Signal Noise Ratio (PSNR) and Structural Similarity Index Metric (SSIM) measure the structural similarity between the original and processed image and do not specifically reflect the resemblance of the edge content. Most of the IQA indices either do not comply with the subjective quality ratings or they are prone to noise level. In the proposed Morphological Edge Similarity Index (MESI), the binary edge maps of the reference and processed images are generated via gradient based threshold and these edge maps are objectively compared to yield a reliable edge quality metric. The index is found superior to Edge Preservation Index (EPI), Edge Strength Similarity based Image quality Metric (ESSIM) and SSIM in terms of dynamic variability, correlation with subjective quality ratings, robustness to noise and sensitivity to degradation in edge quality caused by blockiness artefacts in image compression. MESI exhibits a correlation of 0.9985, very close to unity, with the subjective quality ratings. It is useful for objectively evaluating the performance of denoising, sharpening and enhancement schemes and for the selection of optimum value of the arbitrary parameters used in them.

4

Synthesis, Characterization, DNA Binding and Cleavage Studies of Some Novel Biosensitive Transition Metal(II) Complexes

Raman R., Joseph J.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 7

1303-1311

EN

Four novel Knoevenagel type Cu(II), Ni(II), Co(II) and Zn(II) macrocyclic complexes derived from 3-cinnamalideneacetoacetanilide and N-(2-aminoethyl)-1,3-propanediamine have been synthesized. The nature of complexes and the geometry have been inferred from their microanalytical data, magnetic susceptibility measurements, IR, UV-Vis., 1H NMR, ESR and mass spectral techniques. The low electrical conductance of complexes supports their neutral nature.Monomeric nature of the complexes is assessed from theirmagnetic susceptibility values. The in vitro biological screening effects of the investigated compounds were tested against the bacteria E. coli, S. aureus, S. typhi and K. pneumoniae by the well diffusion method using agar nutrient as the medium. A comparative study of MIC values of the macrocyclic Schiff base ligand and its complexes indicates that the complexes exhibit higher antibacterial activity than the free ligand. The cyclic voltammetry method was used to probe the interaction of a Cu(II) complex with pUC18 DNA. Information of the binding ratio and intercalation mode can be obtained from its electrochemical data. Cyclic voltammetric measurements showed that Cu(II) complex undergoes a reversible reduction at biologically accessible potentials. From the study, it is understood that copper complex prefers to bind with DNAin Cu(II) rather than Cu(I) oxidation state. The DNAcleavage ability of the complexes was monitored by gel electrophoresis using super coiled pUC18 DNA in Tris-HCl buffer.