title: Planning in the IGRT context: closing the loop.
abstract: Technological developments in image-guided radiotherapy systems have introduced new considerations to the treatment-planning process. These include more rational assessment and reduction of treatment margins; adaptation of treatment plans according to information gathered as treatment progresses; and facilitation of treatments involving the delivery of large, highly focused doses of radiation to tumors. We examine the performance of different treatment-room image-guidance systems in terms of target position accuracy; such information is important for determining treatment margins and deciding on an appropriate correction strategy. Some clinical situations may warrant a modification to a patient's treatment plan part way through a course of treatment, such as tumor shrinkage in response to treatment and daily organ variation. We discuss the challenges and review proposed strategies for treatment-plan adaptation. Image guidance in combination with 3-dimensional conformal and intensity-modulated radiotherapy has provided the tools for clinical trials of single-dose and hypofractionated treatment as an alternative to standard fractionation. We discuss the clinical realization of this treatment paradigm in various disease sites.
authors: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. magerasg@mskcc.org
authors: Gig S
authors: GS
authors: Mageras
authors: James
authors: J
authors: Mechalakos
mesh_terms: D003952:Diagnostic Imaging; D019583:Dose Fractionation, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D008113:Liver Neoplasms / Q000532:radiotherapy; D008175:Lung Neoplasms / Q000532:radiotherapy; D008297:Male; D009369:Neoplasms / Q000532:radiotherapy*; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed