According to the basic knowledge of the information theory, noise is known to hinder signal quality, and as the noise level increases the signal detection sensitivity decreases. Noise has a detrimental effect on tasks involving vigilance, memory and divided attention. Its effects vary depending on the nature of the noise (including volume, predictability and perceived control) and the type of task that participants are asked to undertake. Rician noise introduces a bias into MRI measurements that can have a significant impact on the cardic magnetic resonance (CMR) image segmentation. Noting to the variations of the noise with the signal amplitude, this paper discusses the over all effect of noise on segmentation. The eigen values that describe the contrast of the image are shown to have been decreased with the addition of noise. The presence of heavy noise is shown to lead to an under segmentation.Index Terms-Cardiac magnetic resonance image, noise, eigen values, variogram, power spectral density.