title: The effect of image-guided radiation therapy on the margin between the clinical target volume and planning target volume in lung cancer.
abstract: IntroductionThis study aimed to evaluate the effect of image-guided radiation therapy (IGRT) on the margin between the clinical target volume (CTV) and planning target volume (PTV) in lung cancer. MethodsThe CTV and PTV margin were determined in three dimensions by four radiation oncologists using a standard method in 10 lung cancer patients, and compared to consensus values. Transfer error was measured using a rigid phantom containing gold markers. Systematic error ([Formula: see text]) and random error ([Formula: see text]) set up errors were calculated in three dimensions from pre-treatment and post-treatment cone beam CT scans. Finally, the margin between the CTV and PTV was corrected for set up error and calculated. ResultsThe margins between the CTV and PTV with IGRT (and without IGRT) were 0.88 cm (0.96 cm), 0.99 cm (1.08 cm) and 1.28 cm (1.82 cm) in the anterior and posterior (AP), left and right (LR) and superior and inferior (SI) directions, respectively. Images from two other patients verified the validity of the corrected margin. The target delineation errors of the radiation oncologists are considered to be the largest compared with the set up errors. The application of IGRT reduced the set up errors and the margins between CTV and PTV. ConclusionsThe delineation errors of radiation oncologists are the most important factor to consider for the margin between CTV and PTV for lung cancer. IGRT can reduce the margins by reducing the set up errors, especially in the SI direction. Further research is required to assess whether the reduction in the margin is solely based on set up errors.
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liang
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Minghui
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Han
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Dongfu
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Zhouguang
authors.initials: Z
authors.lastname: Hui
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Jima
authors.initials: J
authors.lastname: Lv
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Liansheng
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zheng
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Jianrong
authors.initials: J
authors.lastname: Dai
authors.affiliation: Department of Radiotherapy, Cancer Hospital, Chinese Academy of Medical Sciences Beijing, China.
authors.forename: Luhua
authors.initials: L
authors.lastname: Wang
keywords: Image-guided radiotherapy; lung neoplasm; set up error; target volume