Image-guided Radiation Therapy

Image-guided radiation therapy (IGRT) is the process of frequent two and three-dimensional imaging, during a course of radiation treatment, used to direct radiation therapy utilizing the imaging coordinates of the actual radiation treatment plan. The patient is localized in the treatment room in the same position as planned from the reference imaging dataset. An example of Three-dimensional (3D) IGRT would include localization of a cone-beam computed tomography (CBCT) dataset with the planning computed tomography (CT) dataset from planning. Similarly Two-dimensional (2D) IGRT would include matching planar kilovoltage (kV) radiographs fluoroscopy or megavoltage (MV) images with digital reconstructed radiographs (DRRs) from the planning CT.

This process is distinct from the use of imaging to delineate targets and organs in the planning process of radiation therapy. However, there is clearly a connection between the imaging processes as IGRT relies directly on the imaging modalities from planning as the reference coordinates for localizing the patient. The variety of image gathering hardware used in planning includes Computed Tomography(CT), Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET) among others. Through advancements in imaging technology, combined with a further understanding of human biology at the molecular level, the impact of IGRT on radiotherapy treatment continues to evolve.