Abstract

PITA MACHADO, Reinaldo et al. Improving head CT image quality by use of Wavelet filters. EAC [online]. 2012, vol.33, n.1, pp. 56-62. ISSN 1815-5928.

An algorithm to reduce Poisson noise is described using Wavelet filters. Five tomographic images of patients and a head anthropomorphic phantom were used. They were acquired with two different CT machines. Due to the original images contain the acquisition noise; some simulated free noise lesions were added to the images and after that the whole images were contaminated with noise. Contaminated images were filtered with 9 Wavelet filters at different decomposition levels and thresholds. Image quality of filtered and unfiltered images was graded using the Signal to Noise ratio, Normalized Mean Square Error and the Structural Similarity Index, as well as, by the subjective JAFROC methods with 5 observers. Some filters as Bior 3.7 and dB45 improved in a significant way head CT image quality(p<0.05) producing an increment in SNR without visible structural distortions.

Keywords : poisson Noise; wavelet transform; brain CT; JAFROC.

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