Linear and Nonlinear Models and Algorithms in Intensity-Modulated Radiation Therapy (IMRT)

IMRT, abbreviating Intensity-Modulated Radiation Therapy, refers to a method of introducing spatial variation in the intensity (analogous to flow) of radiation directed across a beam front based on desired objectives concerning the resulting dose distribution within the body. Dose, like temperature, is a quantity that can be attached to each point of an irradiated body. The distribution of dose over critical organs and tumor targets bears a relation, 1 albeit imperfect, to end-goals such as rates of complication and cure. The principles underlying the new IMRT approach are that treatment parameters (such as machine settings) can be arranged to yield an intensity map for each incident beam, that an accurate dose distribution can be determined from knowledge of all the beam intensity maps, and that some dose distributions are preferred over others. Linearity enters because the contributed dose is a linear combination of the intensities carried by the infinitesimally small elements of the beam