While working in Rutherford’s laboratory in Manchester, England, de Hevesy performed an unsuccessful experiment that nevertheless led to the very important conclusion that it is impossible to isolate by chemical means a radioactive isotope from the element of which it is part. Since the radioactive atoms remain the faithful companions of the nonradioactive atoms of the same element, he suggested that a radioactive isotope’s characteristic radiation could serve as a special “marker.” This radioactive marker, or tracer, follows its companion nonradioactive atoms throughout a living system, as they experience various biophysical and biochemical processes. Because radiation detectors can observe the presence of minute quantities of ionizing radiation, even a very tiny amount of radioactive material mixed in with nonradioactive atoms of the same element is sufficient as a tracer. De Hevesy received the 1943 Nobel Prize in chemistry for developing this important nuclear technology application.
Starting in the 1930s, the creation of artificial radioactive isotopes greatly expanded the application of de Hevesy’s tracer principle in medicine, industry, and science. For example, three radioisotope tracers— carbon-14, tritium, and phosphorous-32––played a major role in the establishment of modern biochemistry after World War II. These tracers remain the backbone of contemporary biological science. Similarly, the tracers carbon-11, iodine-123, fluorine-18, and technetium-99m used with PET (positron emission tomography) and SPECT (single-photon emission computed tomography)—discussed shortly—are key tools for in vivo biochemistry research and nuclear medicine applications. In vivo procedures occur when health care workers give trace amounts of radiopharmaceuticals (medical radioisotopes) directly to a patient. A radiopharmaceutical is the basic radioactively tagged compound (tracer) used to produce a nuclear medicine image. By comparison, an in vitro procedure takes place outside the patient’s body in a test tube. For example, radioimmunoassay (RIA) is a special type of in vitro procedure that combines the use of radioactive chemicals and antibodies to measure the levels of hormones, drugs, and vitamins in a patient’s blood.
Nuclear Impasse Remains If US Continues to Keep the Sanctions to Cripple Iranian Economy
