Multimodality Image-Guided Radiotherapy of the Liver

Technological advances have made it possible for tumoricidal doses of radiation to be delivered to primary and metastatic liver cancers. Computed tomography, magnetic resonance imaging, ultrasound and positron emission tomography are used to help with tumor definition at the time of radiation planning. Specialized imaging techniques are also used for characterization of tumor motion due to breathing at the time of radiation planning. Image-guided radiation therapy (IGRT), referring to the use of frequent imaging in the treatment position during a course of radiotherapy to localize the tumor prior to or during each treatment, improves accuracy and precision of radiation delivery. IGRT improves the concordance between the delivered doses to the tumor and normal tissues and the planned doses, which should improve our understanding of dose–outcome analyses. IGRT also reduces the volume of normal tissue that needs to be irradiated, and facilitates dose escalation to the tumor, potentially improving tumor control probability and reducing the risk of toxicity. Image registration is required to bring imaging data sets together at the time of radiation planning and also for image guidance at treatment. This study provides an overview of multimodality imaging and IGRT used in liver cancer conformal radiation therapy.