Image-guided radiation therapy (IGRT): practical recommendations of Italian Association of Radiation Oncology (AIRO).

The use of imaging to maximize precision and accuracy throughout the entire process of radiation therapy (RT) delivery has been called "Image-guided RT" (IGRT). RT has long been image guided: in fact, historically, the portal films and later electronic megavoltage images represented an early form of IGRT. A broad range of IGRT modalities is now available and adopted. The target location may be defined for each treatment fraction by several methods by localizing surrogates, including implanted fiducial markers, external surface markers or anatomical features (through planar imaging, fluoroscopy, KV or MV computed tomography, magnetic resonance imaging, ultrasound and X-ray imaging, electromagnetic localization, optical surface imaging, etc.). The aim of the present review is to define practical recommendations for IGRT.