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Patient‐specific quantification of respiratory motion‐induced dose uncertainty for step‐and‐shoot IMRT of lung cancer
Author(s) -
Li Heng,
Park Peter,
Liu Wei,
Matney Jason,
Liao Zhongxing,
Balter Peter,
Li Yupeng,
Zhang Xiaodong,
Li Xiaoqiang,
Zhu X. Ronald
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4829522
Subject(s) - dosimetry , nuclear medicine , medicine , breathing , radiation treatment planning , radiation therapy , lung cancer , cumulative dose , standard deviation , radiology , mathematics , oncology , anesthesia , statistics
Purpose: The objective of this study was to quantify respiratory motion‐induced dose uncertainty at the planning stage for step‐and‐shoot intensity‐modulated radiation therapy (IMRT) using an analytical technique.Methods: Ten patients with stage II/III lung cancer who had undergone a planning four‐dimensional (4D) computed tomographic scan and step‐and‐shoot IMRT planning were selected with a mix of motion and tumor size for this retrospective study. A step‐and‐shoot IMRT plan was generated for each patient. The maximum and minimum doses with respiratory motion were calculated for each plan, and the mean deviation from the 4D dose was calculated, taking delivery time, fractionation, and patient breathing cycle into consideration.Results: For all patients evaluated in this study, the mean deviation from the 4D dose in the planning target volume (PTV) was <2.5%, with a standard deviation <1.2%, and maximum point dose variation from the 4D dose was <6.2% in the PTV assuming delivery dose rate of 200 MU/min and patient breathing cycle of 8 s. The motion‐induced dose uncertainty is a function of motion, fractionation, MU (plan modulation), dose rate, and patient breathing cycle.Conclusions: Respiratory motion‐induced dose uncertainty varies from patient to patient. Therefore, it is important to evaluate the dose uncertainty on a patient‐specific basis, which could be useful for plan evaluation and treatment strategy determination for selected patients.