A bioassay is a medical test to measure, and quantify radionuclides in the body by direct (in vivo) or indirect (in vitro) analysis of tissues or excretions from the body.

See also Radioimmunoassay.

Atomic or nuclear fission is the process of splitting a heavy nucleus into two lighter nuclei. Some nuclides split up spontaneous as a type of radioactive decay. In other elements, fission is induced through the reaction of an incident radiation with the nucleus. High energy rates are released during the fission reaction (difference between the binding energies); this energy is used to produce heat and electricity e.g. in nuclear power plants.

(GBPS) The gated blood pool scintigraphy is an examination to evaluate the ventricular performance. This scintigraphic blood pool imaging uses an electrocardiographic synchronizer or gating device to acquire data during repeated heart cycles at specific times in the heart cycle. Radionuclides, for example 99mTc-humanserumalbumin (HSA), are used as intravascular tracers.
GBPS allows to determinate the left ventricular function with heart minute volume, ejection fraction (EF) at rest and under exercise. Single photon emission computed tomography (SPECT) versus planar scintigraphic imaging improves cardiac evaluation due to the three dimensional nature. The GBPS method is not suitable to analyze the right ventricular function; that is best evaluated by first-pass ventriculography.
Echocardiography vs. GBPS has important disadvantages due to problems in quantitative evaluation, in patients with anatomic variations and dyskinetic left ventricles.

See also Myocardial Perfusion Imaging.

Ion particles accelerated in a cyclotron are diverted by a magnetic field to a circular course until a desired energy is reached. The ion beam resulting from this procedure is e.g. used for the production of radionuclides.

See also Ion, Cyclotron.

Isomers are nuclides with the same number of neutrons and protons of a given element in different states of excitation. Most of these unstable isomers decay very quickly (~ 10^-12 seconds).
They are characterized in the chemical formula by an m (e.g. Tc-99m).

See also Isomeric Transition.