Gamma rays are a form of nuclear radiation that consists of photons emitted by radioactive elements from the nucleus. This high energetic light emission is also produced from subatomic particle interaction, such as electron positron annihilation. Gamma radiation, similar to x-radiation can injure and destroy tissue, especially cell nuclei.
Gamma rays have in general very high frequencies, short wavelengths, are electrically neutral and penetrate matter. The interaction of gamma rays with matter depends on the nature of the absorber as well as the energy of the gamma rays; these interactions determine also the type and amount of shielding needed for radiation protection.

See also Radiation Safety, Lead Equivalence, Lead Apron, Leaded Glove, Glove-Box, Radioactive Decay Law and Radiation Worker.

(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.

The common radionuclide used for inflammation scintigraphy is 67Ga-citrate, which accumulates in inflammatory lesions and certain neoplasms. A 67 gallium scan may include scintigrams of the whole body or a specific region, performed after i.v. injection. Additionally, a single photon emission computed tomography (SPECT) can be performed. A pathological process presents itself as activity enrichment.

The intrinsic conversion efficiency is the efficacy of an intensifying screen in converting x-rays into light photons.
For example, the radiation to light conversion efficiency of calcium tungstate is less than the efficiency of rare earth screens (about 5% vs. 12 - 18%).

Leukocyte scintigraphy is a medical imaging test which displays the distribution of radiolabeled (for example labeled with 111In indium) leukocytes in the body to detect infection / inflammation. Whole-body scintigrams, and/or images of specific anatomic regions are recorded. Additionally, single photon emission computed tomography can be obtained.

See also Granulocyte Scintigraphy and Abscess Scintigraphy.