The World Health Organization has defined Nuclear Medicine as taken to embrace all applications of radioactive materials in diagnosis or treatment or in medical research, with the exception of the use of sealed radiation sources in radiotherapy. The precise starting point of Nuclear Medicine is difficult to define but radioactive iodine was being used in studying thyroid disease in the late 1940s, and by the mid 1950s thyroid gland images and isocount curve plotting were developed steadily into a firmly based clinical and scientific discipline. The greatest impetus to this development has been in the United States, other countries such as Canada, Japan and Germany have followed.

In Hong Kong Nuclear Medicine started as earlier as 1957, one of the earliest in Asia. The service was originally under the Radiotherapy Division of the Institute of Radiology and Oncology and known as the Radioisotope Section. In the mid 1970s , radionuclide imaging service was then transferred to be under the Diagnostic Radiology Division of the Institute. Since there was no radiologists or radiotherapists interested to specialize in Nuclear Medicine, the development was very slow even up to the year 1980. Dr. John H.C. Ho, who was then in charge of the Institute, was aware of the problem and a proposal was made to form an independent Nuclear Medicine Division under the Institute, embracing radionuclide imaging, functional tests and therapy. In 1984, Dr. David W.C. Yeung was appointed as Consultant in Nuclear Medicine in charge of the Nuclear Medicine Section. Since then, the service of Nuclear Medicine was under the supervision and development of the Consultant in Nuclear Medicine. In 1985, the Hong Kong Society of Nuclear Medicine was formed. Nuclear Medicine was first regarded as a specialty in 1988 in a government report on post-graduate medical education and training.

Nuclear Medicine is now regarded as a specialty with its own local training programme and postgraduate qualifying examinations. It is one of the three specialties under the Hong Kong College of Radiologists. The training pathway for a trainee Nuclear Medicine physician has now been fully established. It takes a minimum of six years to complete the postgraduate training. After getting basic medical degrees and internship, two years are spent in basic training which includes one year of elective training in a clinical specialty. This is followed by the Part I Fellowship Examination in Nuclear Medicine. Afterwards there are two years of intermediate training which includes six months of elective training in diagnostic radiology. After passing the Part II Fellowship Examination, two more years will be spent in higher training. On completion of training, the trainee will be awarded Fellow of the Hong Kong College of Radiologists and Fellow of the Hong Kong Academy of Medicine (Radiology) and be regarded as a specialist in Nuclear Medicine.