Image-Guided Radiation Therapy

Image-guided radiation therapy (IGRT) is the process of frequent imaging during a course of radiation treatment, used to direct the treatment, position the patient, and compare the patient's position to the pre-therapy imaging captured during treatment planning. Immediately before or during a treatment fraction the patient is localized in the treatment room to match the position planned from the reference imaging dataset, for example by comparing a cone beam computed tomography dataset acquired on the treatment machine with the computed tomography dataset from planning, or by matching planar kilovoltage or megavoltage images with digital reconstructed radiographs from the planning CT. IGRT is distinct from the use of imaging to delineate targets and organs during the planning process itself, though the two are connected because IGRT relies on the planning imaging as its reference coordinates; it can help reduce errors in patient set-up and positioning, allow the margins around target tissue to be reduced during planning, and enable treatment to be adapted over its course, with the aim of improving overall outcomes.