**2. Medical uses of radiopharmaceuticals**

A radionuclide may decay by emitting different types of ionising radiation: alpha (α), beta (β-), positron (β+) and gamma (γ) radiation.

Depending on the radiation characteristics of the radionuclide, the radiopharmaceutical is used either for diagnosis or for therapy. Diagnostic radiopharmaceuticals should decay by gamma emission like Technetium-99 m (99mTc), Iodine-123 (123I) and Galium-67 (67Ga) or positron emission like Fluorine-18 (18F), Oxygen-15 (15O), Carbon-11 (11C), Zirconium 89 (89Zr) and Gallium 68 (68Ga) and never emit alpha particles or even beta particles.

On the other hand, therapeutic radiopharmaceuticals should decay by particulate decay (alpha or beta) since the intended effect is in fact radiation damage to specific cell, examples of β -emitters are Rhenium-186/Rhenium-188 (186Re/188Re), Strontium-89 (89Sr), Lutetium-177 (177-Lu),Iodine-131 (131-I) and Yttrium-90 (90Y) and of therapeutic α-emitters are Actinium-225 (225Ac), Bismuth-213 (213Bi) and Astatine-211 (211At).

Moreover, there is an emerging field of nuclear medicine named theranostics (Therapeutics and diagnostics), that involves diagnostic and therapeutic agents to target diseased cells and tissues. The use of targeting molecules labelled either with diagnostic radioisotopes and with therapeutic isotopes enables a more complete approach to patient management, because the diagnosis can then serve several simultaneous functions: assessing disease, monitoring and selection for therapy. The prospects of identifying the disease and orienting treatment, provide an advance level in precision medicine.

One of the most common examples of theragnosis in nuclear medicine is the use of Gallium 68(68Ga) as a diagnostic radiopharmaceutical, followed by therapy with radionuclides such as Lutetium 177 (177-Lu) to label the same molecule in the context of personalised therapy.
