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FIGURE 2. Different tissue absorption properties of photons versus electron or 
-particle emissions of radionuclide are illustrated. Photons originating in liver, for example, depending on energy, can irradiate distant organs. Correspondingly, not all of photon energy emitted within source organ will be absorbed by source organ, as reflected in possible range of absorbed fraction values for photons. In contrast, great majority of electron (Auger and ß-particles) or -particle energy will be absorbed very close to emission source and within source tissue. Correspondingly, energy absorption to other tissues is negligible.
