Radiopharmaceutical

Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes.

Radiopharmaceuticals emit radiation themselves, which is different from contrast media which absorb or alter external electromagnetism or ultrasound.

The main group of these compounds are the radiotracers used to diagnose dysfunction in body tissues.

While not all medical isotopes are radioactive, radiopharmaceuticals are the oldest and remain the most common of such drugs.

It is produced in medical cyclotrons, usually from oxygen-18, and then chemically attached to a pharmaceutical formulation.

68Ga is a positron emitter, with a 68-minute half-life, produced by elution from germanium-68 in a gallium-68 generator or by proton irradiation of zinc-68.

Thyroid metastases imaging 125I is a gamma emitter with a long half-life of 59.4 days (the longest of all radioiodines used in medicine).

Iodine-123 is preferred for imaging, so I-125 is used diagnostically only when the test requires a longer period to prepare the radiopharmaceutical and trace it, such as a fibrinogen scan to diagnose clotting.

I-125's gamma radiation is of medium penetration, making it more useful as a therapeutic isotope for brachytherapy implant of radioisotope capsules for local treatment of cancers.

It can also be seen by a gamma camera, and can serve as a diagnostic imaging tracer, when treatment is also being attempted at the same time.