The three-volume set LNCS 7510, 7511, and 7512 constitutes the refereed proceedings of the 15th International Conference on Medical Image Computing and Computer-Assisted Intervention, MICCAI 2012, held in Nice, France, in October 2012. Based on rigorous peer reviews, the program committee carefully selected 252 revised papers from 781 submissions for presentation in three volumes. The first volume includes 91 papers organized in topical sections on abdominal imaging, computer-assisted interventions and robotics, computer-aided diagnosis and planning, image reconstruction and enhancement, analysis of microscopic and optical images, computer-assisted interventions and robotics, image segmentation, cardiovascular imaging, and brain imaging: structure, function and disease evolution.