A major problem in magnetic resonance imaging (MRI) is the lack of a pulse sequence dependent standardized intensity scale like the Hounsfield units in computed tomography. This affects the post processing of the acquired images as, in general, segmentation and registration methods depend on the observed image intensities. Different approaches dealing with this problem were proposed recently. In this article we will describe and compare five state-of-the-art standardization methods regarding speed, applicability and accuracy. As a quality measure the mean distance and the Kullback-Leibler divergence are considered. For the experiments 28 MRI head volume images, acquired during clinical routine, were used.