In the internal conversion process the multipole electric field of the nucleus of an atom, in an electromagnetically excited state, react with an orbit electron. With enough energy the electron is ejected (internal conversion electron). The energy of the conversion electron depends on the energy transferred from the nucleus reduced by the shell specific binding energy. This process competes with gamma emission. The refilling for the vacancy left by the internal conversion electron occurs through the Auger effect, a higher orbit electron take place and x-ray or an Auger electron will be emitted.
The atomic number of the atom gets not changed by internal conversion.

See also Conversion Electron, Auger Effect and Auger Electron.

Isobars are atoms with equal mass number but different atomic number.

(AMU) is equal to the mass of one-twelfth of a carbon-12 atom (6 protons + 6 neutrons (+ 6 electrons)), a 'very' little less than 1.66 x 10^-24 gram.

See also Mass Number and Atomic Mass.

(CA) Contrast agents are used to change the imaging characteristics, resulting in additional information about anatomy, morphology or physiology of the human body. Radiocontrast agents (also called photon-based imaging agents) are used to improve the visibility of internal body structures in x-ray and CT procedures. Contrast agents are also used to increase the contrast between different tissues in MRI (magnetic resonance imaging) and ultrasound imaging. The ideal imaging agent provides enhanced contrast with little biological interaction.
First investigations with radiopaque materials are done shortly after the discovery of x-rays. These positive contrast agents attenuate x-rays more than body soft tissues due to their high atomic weight. Iodine and barium have been identified as suitable materials with high radiodensity and are used until today in x-ray and CT contrast agents. Iodine-based contrast agents are water-soluble and the solutions are used nearly anywhere in the body. Iodinated contrast materials are most administered intravenous, but can also be introduced intraarterial, intrathecal, oral, rectal, intravesical, or installed in body cavities. Barium sulfate is only used for opacification of the gastrointestinal tract. Negative contrast agents attenuate x-rays less than body soft tissues, for example gas.

Iodinated contrast media are differentiated in;

Intravascular iodinated contrast agents are required for a large number of x-ray and CT studies to enhance vessels and organs dependent on the blood supply. Injectable contrast agents are diluted in the bloodstream and rapidly distributed throughout the extracellular fluid. The main route of excretion is through the kidneys, related to the poor binding of the agent to serum albumin. The liver (gall bladder) and small intestine provide alternate routes of elimination particularly in patients with severe renal impairment. The use of special biliary contrast agents is suitable for gallbladder CT and cholecystograms because they are concentrated by the liver to be detectable in the hepatic bile.
The introduction of fast multi-detector row CT technology, has led to the development of optimized contrast injection techniques. The amount of contrast enhancement depends on the contrast agent characteristics, such as iodine concentration, osmolality, viscosity, and the injection protocol, such as iodine flux and iodine dose. Adverse reactions are rare and have decreased with the introduction of nonionic contrast agents.
See also Contrast Enhanced Computed Tomography, Abdomen CT, Contrast Media Injector, Single-Head CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector, CT Power Injector.

(K-capture) An unstable atom with too many protons in the nucleus, and not enough energy to emit a positron, reaches a stable state in the way, that one proton captured an electron from the atom's inner shell (K-shell) and change to a neutron. A neutrino is emitted from the atoms nucleus by this process. The atomic mass of the atom is unchanged, but the decreased number of protons transformed the atom to a different element.