This publication was conceived following a scientific meeting on the subject in November 1990. The long gestation period has enabled the editors to commission additional material to ensure that the final product is both comprehensive and up-to-date. Indeed, the editors have actively filtered and smoothed the various contributions to the extent that many of the eight chapters cannot be directly attributable to individual authorships. There is, however, full indication and acknowledgment of the efforts of more than 30 contributors, not all of them physicists.

IPEM: Institute of Physics and Engineering in Medicine