1. A method of correcting registration misalignment in magnetic resonance perfusion images, the method comprising the steps of: receiving a time series of magnetic resonance images of an anatomical organ, each said image comprising a plurality of intensities defined on an N-dimensional domain of points; performing a first group-wise registration of all images in the time series of images, using a pair-wise registration as an initialization; detecting a misaligned image from said group-wise registration by analyzing a total variation of intensity differences between consecutive images; and correcting said misaligned image by optimizing a second group-wise energy function over registration parameters of said misaligned image, wherein correcting said misaligned image comprises finding a set of rigid registration parameters P i =[p ik ], k=1,. .. , 6, of said misaligned transformation T i that minimizes {E(P(P i ))|P n , n≠i} wherein P=[P 1 , P 2 ,. .. , P N ] is the set of registration parameters for all the images from said first group-wise registration wherein Nis a total number of images, E(P(P i )) is said second group-wise energy function calculated for P with varying P i and fixing P n , with n≠i.