This book discusses certain selected topics in the field of nuclear medicine. Nuclear medicine is the special branch of medicine which is concerned with the use of radioactive substances in research, diagnosis, and treatment. The progress of nuclear medicine as a medical specialty has led to the wide-scale application of its efficient imaging means in daily practice as an elementary method of diagnosis. The introduction of positron-emitting tracers (PET) has depicted another important leap ahead in the capability of nuclear medicine to exercise a thorough effect on patient administration, while the capacity to attain radioisotopes of various elements sparked the beginning of a diverse area of tracer studies in biology and medicine, easing the enhanced interactions of nuclear medicine specialists and specialists in other disciplines. In this age, nuclear medicine has become an important part of diagnosis of various diseases, especially in cardiologic, nephrologic and oncologic applications and it is congenital in its therapeutic approaches, markedly in the cure of thyroid cancers. Data from authorized sources of many countries validate that nearly 10-15 percent of expenditures on clinical imaging studies are used up on nuclear medicine procedures.