The physician wants to maximize radiation dose to the tumor and, at the same time, minimize radiation damage to the patient's healthy tissue . Click on the image for a larger view.
Patient dosimetry is the accurate determination of the radiation dose given during radiotherapy.
The equipment used today to perform radiotherapy, such as the electron electron accelerator , is very complex. The actual radiation dose to the patient and to the tumor is very dependent upon the radiation scattering from components inside the machine as well as structures within the human body. Consider a cross section of the human body as shown in the diagram on the right. The organs in the body can be viewed as discrete units, each with boundaries and densities. Most tissue in the body has a density close to water.