Wilhelm Roentgen is credited with the discovery of radioactivity in 1895 with many others such as Antoine Henri Becquerel, Pierre Curie, and Marie Curie following closely behind to further advance the field of radioactivity. John Lawrence, a physicist at The University of California Berkeley, first used nuclear medicine in humans came in 1936 after extensive use of radioactive phosphorus in mouse models. Often called the father of nuclear medicine, Lawrence treated a leukemia patient with radiophosphorus, which was the first time a radioactive isotope has been used to treat human patients. Another pioneer in the field, Sam Seidlin, in partnership with Saul Hertz, treated a case of thyroid cancer with radioactive iodine (I-131) 1946. In the 1950s, nuclear medicine began to gain traction as a medical specialty with the Society of Nuclear Medicine forming in 1954 and later releasing the first copy of the Journal of Nuclear Medicine in 1960. The use of radioligands and nuclear tagging started to gain popularity in in the early 1960s when Elwood Jensen and Herbert Jacobsen (1962) and later Jack Gorksi, David Toft, G, Shymala, Donald Smith, and Angelo Notides (1968) attempted to identify the estrogen receptor. The American Medical Association (AMA) officially recognized Nuclear Medicine as a medical specialty in 1970 and the American Board of Nuclear Medicine was established in 1972. Progress came quickly in 1973 when Edward Hoffman, Michael M. Ter-Pogossian, and Michael E. Phelps invented the first PET camera for human use. The 1980s brought early radioligand studies for neuroendocrine tumors (NETs) which continued into the early 2000s. In 2017 the European Union (EU) approved the use of radioligand therapy for NETs with the U.S. following close behind in 2018.