Open AccessEffect of MU‐weighted multi‐leaf collimator position error on dose distribution of SBRT radiotherapy in peripheral non‐small cell lung cancer
Author(s) -
Feng AiHui,
Chen Hua,
Wang Hao,
Gu HengLe,
Shao Yan,
Duan YanHua,
Ying YanChen,
Yue Ning Jeff,
Xu ZhiYong
Publication year - 2020
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.13061
Subject(s) - collimator , nuclear medicine , medicine , position error , radiation treatment planning , radiation therapy , position (finance) , dosimetry , stereotactic radiotherapy , radiosurgery , mathematics , physics , radiology , optics , statistics , calibration , finance , economics
Purpose Position accuracy of the multi‐leaf collimator (MLC) is essential in stereotactic body radiotherapy (SBRT). This study is aimed to investigate the dosimetric impacts of the MU‐weighted MLC positioning uncertainties of SBRT for patients with early stage peripheral non‐small cell lung cancer (NSCLC). Methods Three types of MLC position error were simulated: Type 1, random error; Type 2, system shift, in which both MLC banks shifted to the left or right direction; and Type 3, in which both MLC banks moved with same magnitudes in the opposite directions. Two baseline plans were generated: an automatic plan (AP) and a manually optimized plan (MP). Multi‐leaf collimator position errors were introduced to generate simulated plans with the preset MLC leaf position errors, which were then reimported into the Pinnacle system to generate simulated plans, respectively. The dosimetric parameters (CI, nCI, GI, etc.) and gEUD values of PTV and OARs were calculated. Linear regression between MU‐weighted/unweighted MLC position error and gEUD was performed to obtain dose sensitivity. Results The dose sensitivities of the PTVs were −4.93, −38.94, −41.70, −55.55, and 30.33 Gy/mm for random, left shift, right shift, system close, and system open MLC errors, respectively. There were significant differences between the MU‐weighted and the unweighted dose sensitivity, which was −38.94 Gy/mm vs −3.42 Gy/mm (left shift), −41.70 Gy/mm vs −3.56 Gy/mm (right shift), −55.55 Gy/mm vs −4.84 Gy/mm (system close), and 30.33 vs 2.64 Gy/mm (system open). For the system open/close MLC errors, as the PTV volume became larger, the dose sensitivity decreased. APs provided smaller dose sensitivity for the system shift and system close MLC errors compared to the conventional MPs. Conclusions There was significant difference in dose sensitivity between MU‐weighted and unweighted MLC position error of SBRT radiotherapy in peripheral NSCLC. MU is suggested to be included in the dosimetric evaluation of the MLC misalignments, since it is much closer to clinical radiotherapy.