Comparison of rigid and elastic matching of dynamic magnetic resonance mammographic images by mutual information

The present study aims at (i) the evaluation of the performance of a rigid and of an elastic matching algorithm for the coregistration of dynamic magn etic resonance (MR) images visualizing the female breast, and (ii) the eval uation of the mutual information (MI) as a matching criterion. To this end, ten patient data sets were analyzed. The comparison was performed with res pect to the achieved increase in the MI and by visual inspection of the dyn amic image series in a continuous film sequence (cine mode). In most cases, the achieved increase in MI by elastic image registration is much higher t han that achieved by rigid registration. Only for three of the ten data set s could the MI be increased by rigid image registration to a similar or eve n larger degree than by elastic image registration. Taking into account the results of the visual inspection of the rigid and elastic matched data set s, however, the elastic match leads to equal or better results for all data sets. Therefore, elastic matching is the gold standard for the registratio n of dynamic MR mammographic images of the female breast. The comparison of the increase in MI and the visual inspection further shows that the visual impression agrees in most cases with the result of the calculation of the MI. Therefore, the MI proves to be a suitable matching criterion for the ty pe of data sets studied. (C) 2000 American Association of Physicists in Med icine. [S0094-2405(00)00309-6].