title: Intrafractional tumor motion: lung and liver.
abstract: Three-dimensional (3D) dose distribution has been improved by 3D conformation and intensity modulation in external radiotherapy. Interfractional uncertainty has been reduced by image-guided setup techniques. Reduction of ambiguity because of intrafractional target motion is the next step forward. Respiratory organ motion is known to be the largest intrafractional organ motion. Radiotherapy techniques controlling, gating, or tracking respiratory motion are under investigation to use smaller safety margins and higher doses for moving tumors. However, data on intrafractional tumor motion are sparse. We developed a fluoroscopic real-time tracking system and implantation techniques of fiducial markers for moving organs and have been accumulating knowledge about internal tumor motion. We also found the importance of 4-dimensional treatment planning to account for tumor motion in precision radiotherapy. This article reviews the current basic knowledge on respiratory physiology and summarizes the accumulating knowledge on internal motion of lung and liver tumors.
authors.affiliation: Department of Radiology, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
authors.forename: Yvette
authors.initials: Y
authors.lastname: Seppenwoolde
authors.forename: Kei
authors.initials: K
authors.lastname: Kitamura
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimura
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
mesh_terms: D005471:Fluoroscopy; D006801:Humans; D008113:Liver Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D009038:Motion; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D012119:Respiration; D012143:Respiratory Physiological Phenomena