This book constitutes the refereed proceedings of the 4th International Conference on Medical Image Computing and Computer-Assisted Intervention, MICCAI 2001, held in Utrecht, The Netherlands, in October 2001. The 122 revised papers and 136 posters presented were carefully reviewed and selected from a total of 338 submissions. The book offers topical sections on image-guided surgery; shape analysis, segmentation, computer-aided diagnosis; registration; simulation, planning and modeling; visualization; quantitative image analysis; medical robotics and devices; visualization and augmented reality; and time series analysis