Image guided radiotherapy moving towards real time adaptive radiotherapy; global positioning system for radiotherapy?

Image guided radiotherapy (IGRT) has been defined as ‘any imaging at the pre-treatment and treatment delivery stage that leads to an action that can improve or verify the accuracy of radiotherapy’ [1]. During the last 30 years, imaging in radiotherapy has reflected the advances of technology in society. We have moved from 2D, film imaging, to digital camera imaging (electronic portal imaging), then to video recording, 3D technology (Computerised Tomography (CT) and Cone Beam CT(CBCT)), more recently the addition of 4D information with location finders, (4D CT, 4D CBCT), and now entering the world of real-time adaptive radiotherapy which promises to be a ‘global positioning system (GPS) for radiotherapy’.