The 1991 International Conference on Information Processing in Medical Imaging (IPMI '91) is the twelfth in the series and was held in Wye College, part of the University of London. The purpose of IPMI is to provide a forum for the detailed examination of methodological issues in computing which are at the heart of advances in medical image formation, manipulation and interpretation. This volume presents the proceedings of IPMI '91. Full-length scientific papers describing the latest techniques and results are organized into the following nine sections: - Image formation and reconstruction -...