Radiation Pneumonitis and Fibrosis

Radiation pneumonitis represents an acute or subacute process following radiotherapy that may be reversible. Fibrosis is a more chronic process that may continue to evolve up to 2 years after treatment. To avoid confusion with other parenchymal opacities that may be encountered post-radiation, one must understand the technique used for radiotherapy in the thorax including: traditional, three-dimensional conformal radiation therapy (3D-CRT), and stereotactic beam radiation therapy (SBRT). The goal of this chapter is to review these different techniques so that expected findings can be distinguished from more significant imaging abnormalities.