Parmenides said that what cannot be thought, cannot be, therefore, what can be, can be thought. So it was that ancient Greek philosophers had thought of the atoms, and particularly, the radioactive atoms we use in Nuclear Medicine. Indeed, Democritos in the sixth century bc formulated the idea of the atoms as the indestructible smaller elements of the universe that combine among themselves to form the visible world; he thought of atoms on a philosophical basis as the explanation of the changes in the environment, which occur without the perishment of matter. Rearrangements of atoms could explain the changes around us and inside us. Two centuries later, Epicuros, as if anticipating the discovery of the radioactive atoms, introduced the idea of the unstable atom, which, after a period of instability, takes its final stable form. More than 2,000 years later, when science overtook these frontiers, John Dalton knew Democritos' Atomic Theory of Matter and used it to explain chemical experiments. If the atom (=not possible to cut) can be cut and split into parts, it is not Democritos' fault. Today we understand that by atoms Democritos actually meant the quarks or the strings, or perhaps some other, yet to be discovered, elemental particles. As for Henri Beckerel and Marie Curie, who were among the first to deal with radioactivity and the unstable or radioactive atoms, it is not known if they knew that the theoretical father of Nuclear Science was Epicuros. In Nuclear Medicine, we use the radioactive atoms, which are the atoms meant by Democritos (as applied by Dalton), in their unstable form, which was anticipated by Epicuros, for imaging of tissues or diseases and for therapy of malignant or benign diseases.
ASJC Scopus subject areas