Mri Medical Image Denoising by Combined Spectral Subtraction and Wavelet Based Methods

Image denoising is a compromise between the removal of the largest possible amount of noise and the preservation of signal integrity and image resolution. To address this issue, a new hybrid approach is proposed by fusing dual band spectral subtraction and wavelet packet based thresholding method. The dual band spectral subtraction method (SS) is used for preprocessing of noisy MRI images in order to initially reduce the noise level and further the quality of images is improved by wavelet packet based thresholding method. Here threshold value is determined by Stein’s Unbiased Risk Estimator (SURE) and three kinds of thresholding are considered for denoising. According to the computer simulation, the best method of threshold process is obtained by comparing the performance of three wavelet threshold selection rules that are applied to enhance the images. It is suggested from the experimental results that the proposed scheme gives an improved performance, which reflects in better image quality in all types of noisy environment. This approach is incorporated with spatial domain and frequency domain analysis. Results are measured objectively by Peak Signal to Noise Ratio (PSNR), Root Mean Square Error (RMSE), and Universal Quality Index (UQI) and subjectively by measuring the visual quality with Picture Quality Scale (PQS).Overall results indicate that the enhancement quality is performing well in proposed method.