Improvement of CT Image Degraded by Quantum Mottle Using Singularity Detection

Yi-Qiang YANG  Nobuyuki NAKAMORI  Yasuo YOSHIDA  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E86-D   No.1   pp.123-130
Publication Date: 2003/01/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Medical Engineering
Keyword: 
computed tomography (CT),  quantum mottle,  wavelet transform,  patient's dose,  noise reduction,  

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Summary: 
To improve the CT image degraded by radiographic noise (such as quantum mottle), we propose a method based on the wavelet transform modulus sum (WTMS). The noise and regular parts of a signal can be observed by tracing the evolution of its WTMS across scales. Our results show that most of the quantum mottle in the projections of Shepp-Logan phantom has been removed by the proposed method with the supposed cranium well preserved. The denoised CT images show good signal to noise ratio in the region of interest. We also have investigated the relation between the number of X-ray photons and the quality of images reconstructed from denoised projections. From experimental results, this method shows the possibility to reduce a patient's dose about 1/10 with the same visual quality.