1. Cancer Research UK Clinical Magnetic Resonance Research Group, The Institute of Cancer Research, Royal Marsden NHS Foundation Trust, Downs Road Sutton, Surrey, SM2 5PT, United Kingdom, Oxford Instruments Molecular Biotools, Tubney Woods, Abingdon, Oxon, OX13 5QX, United Kingdom, and Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607