Diagnostic radiopharmaceuticals

What are Diagnostic radiopharmaceuticals?

When radiopharmaceuticals are used to help diagnose medical problems, only small amounts are given to the patient. The radiopharmaceutical then passes through, or is taken up by, an organ of the body (which organ depends on what radiopharmaceutical is used and how it has been given). Then the radioactivity is detected, and pictures are produced, by special imaging equipment. These pictures allow the nuclear medicine doctor to study how the organ is working and to detect cancer or tumors that may be present in the organ.

A diagnostic radiopharmaceutical emits radiation called “(gamma) photons”. Like X rays, this special form of light can penetrate the body and detected by an external “camera” that will produce a “picture” which can be used to, for instance, see a tumour or assess the functioning of the lungs.

Diagnostic radiopharmaceuticals are used to determine a disease or disorder.Therapeutic radiopharmaceuticals are used to treat a previously diagnosed disease or disorder. The rule of thumb is that the effective half-life (Te) cannot be longer than the shorter of the physical (Tp) or biological (Tb) half-life.

Radiopharmaceuticals are radioisotopes bound to biological molecules able to target specific organs, tissues or cells within the human body. These radioactive drugs can be used for the diagnosis and, increasingly, for the therapy of diseases.

A radioisotope used for diagnosis must emit gamma rays of sufficient energy to escape from the body and it must have a half-life short enough for it to decay away soon after imaging is completed. The radioisotope most widely used in medicine is Tc-99m, employed in some 80% of all nuclear medicine procedures.