What is Radioactive Dose?
Radiation can come from many sources. There is a natural level of background radiation in the environment. Air travel brings us outside the protection of atmospheric layers that normally shield us from cosmic radiation. If we are injured we may be exposed to medical X-rays. Radioactive building materials and rocks may release radon gas. Finally, there is a artificial radiation resulting from mankind's military activities and the nuclear power industry.
Radioactive dose is a measurement of energy which is deposited in a material from a source of ionizing radiation. Commonly, this is measured in units of rads. Different types of radiation (e.g. alpha, beta, gamma) have different mechanisms for transferring this energy. Therefore, the effects on the body are also dependent on the type of radiation. Radioactive dose provides a physical explanation of energy deposited in a given mass, but it does not explain the effects of that deposited energy into a living organism. For this we require a different measure called the dose equivalent, which modifies a given dose by a quality factor depending on the type of radiation.
The Line-Source and Point-Source Model are used for calculating the absorbed dose for patients receiving radiotherapy. The line-source model is a more practical and realistic approach than the traditional point-source model for evaluating the dose on persons who are exposed to radiation.