Image guidance in radiation oncology treatment planning: The role of imaging technologies on the planning process

Radiation therapy has evolved from 2-dimensional (2D) to 3-dimensional (3D) treatments and, more recently, to intensity-modulated radiation therapy and image-guided radiation therapy. Improvements in imaging have enabled improvements in targeting and treatment. As computer-processing power has improved during the past few decades, it has facilitated developments in both imaging and treatment. The historical role of imaging from 2D to image-guided radiation therapy is reviewed here. Examples of imaging technologies such as positron emission tomography and magnetic resonance imaging are provided. The role of these imaging technologies, organ motion management approaches and their potential impacts on radiation therapy are described.