This book was conceived by Professor K.H. Ephraim, the former director of the Institute for Nuclear Medicine of the University Hospital of Utrecht. Unfortunately, due to a serious illness, he was not able to finish the work he started. He is, however, very pleased to know that the book is, nevertheless, being published. In principle the volume consists of two parts. The first is dedicated to basic science and technology in nuclear medicine. It provides the data which are necessary to a clear understanding of the possibilities and limitations of investigations which make use of radioactive...