ABSTRACT
The effects of ionizing radiation on living organisms are evaluated using the quantity “absorbed dose,” which is the amount of energy deposited per unit mass of any material, in this case living tissue. In most applications in radiation protection and nuclear medicine, dose is averaged over whole organs or tissues. There are specialized applications in which three-dimensional dose distributions or microscopic dose distributions are of interest, but they are mostly related to research application, not daily practical dosimetry. Ionizing radiation may cause DNA damage via direct interaction with components of DNA. The rotation may be in an axial or helical manner; in the latter case, sequential image slices may have various values of “pitch,” which is defined as the ratio of the travel of the imaging table per x-ray tube rotation to the width of the imaging slice. Small animal imaging focuses on testing of new imaging methods and pharmaceuticals to ultimately provide new technology for healthcare delivery to humans.
