It is a great privilege to introduce this book devoted to the current and future roles in research and clinical practice of another exciting new development in MRI: Diffusi- weighted MR imaging. This new, quick and non-invasive technique, which requires no contrast media or i- izing radiation, offers great potential for the detection and characterization of disease in the body as well as for the assessment of tumour response to therapy. Indeed, whereas DW-MRI is already ? rmly established for the study of the brain, progress in MR techn- ogy has only recently enabled its successful application in the body. Although the main focus of this book is on the role of DW-MRI in patients with malignant tumours, n- oncological emerging applications in other conditions are also discussed. The editors of this volume, Dr. D. M. Koh and Prof. H. Thoeny, are internationally well known for their pioneering work in the ? eld and their original contributions to the l- erature on DW-MRI of the body. I am very much indebted to them for the enthusiasm and engagement with which they prepared and edited this splendid volume in a record short time for our series Medical Radiology – Diagnostic section.