In the past years, the development of 3-D medical imaging devices has given access to the 3-D imaging of in vivo tissues, from an anatomical (MR, CT) or even functional point of view (fMRI, PET, SPECT). However, despite huge technological progress, the resolution of these images is still not sufficient to image to anatomical or functional details, that can only be revealed by in vitro imaging (e.g. histology, autoradiography), eventually enhanced by staining. The deep motivation of this work is the comparison of activations detected by fMRI series analysis to the ones that can be observed in autoradiographic images. The aim of the presented work is to fuse the autoradiographic data with the pre-mortem anatomical MR image, to facilitate the above mentioned comparison. First, we reconstruct a 3-D volume, coherent both in geometry and intensity, from the 2-D autoradiographic sections. Second, this volume is fused with the MR image, that allows to geometrically correct the reconstruction to make it comparable to the MR image. We show that this fusion can be achieved by using only simple global transformations (rigid and/or affine, 2-D and 3-D), yielding a very satisfactory result.