Overview of IGRT

The primary goal of image-guided radiation therapy (IGRT) is to improve local control and reduce impending side effects. IGRT provides the ability to ensure that the tumor is being properly targeted while limiting toxicities to normal structures. With the inclusion of IGRT as part of the treatment, the uncertainties arising from target motions can be reduced, whether from inter- or intrafractional motion. Certain systems allow the isodose lines from the plan to be displayed on the imaging obtained during the IGRT procedure. Upon initiation of treatment, IGRT can be used to assess the accuracy of the patient's alignment as well as continually monitor the tumor. An intervention based on IGRT may be required due to setup errors or shifts in the tumor, which could lead to reassessment. Since margins have become tighter and the use of highly modulated plans and dose escalation has increased, IGRT has become a useful tool for detecting any necessary interfractional adjustments.