Estimating the Rician noise level in brain MR image

For an efficient analysis the estimation of the noise level in images is very important to specific estimates of each modality. Moreover, it is a fundamental step and indispensable procedure for a number of image processing approaches. Especially in magnetic resonance images (MRI) due to the Rician presented in these, where the level of noise must be evaluated. In this paper a new method to estimate the noise level in MR images T1-w is proposed and compared with a known level of the ration of signal and noise presented. The advantage of this is its easiness for utilization during image acquisition and of course the adaptability of the idea of other areas of body. The correctness of the evaluation is addressed by comparison of Atlas noise free images where the level of Rician noise was artificially added and known. The main idea is the matching of same slices after registration in order to evaluate the level of noise. For evaluation of the range of noise in an image we used the signal noise ratio - SNR and a set of MRI with increasing levels of Rician noise. However, others metrics like the normalized cross correlation - NCC or the Root Mean Squared Error (RMSE) could be used as well.